RETHINKING THE LESSER BRAIN • THE VAPORS OF …oscar.ayoun.free.fr/www/ebook/Scientific American/2003/Scientific... · The cerebellum does more than coordinate body movement. It

AU GUST 20 03 $4. 95W W W. S CI A M. COM

RETHINKING THE LESSER BRAIN • THE VAPORS OF PROPHECY

Why the

Digital Divide

Does Not

Compute

COPYRIGHT 2003 SCIENTIFIC AMERICAN, INC.

B I O T E C H N O L O G Y

34 Censors of the GenomeB Y N E L S O N C . L A U A N D D A V I D P . B A R T E LBiotechnologists seek new therapies for cancer and other ailments with the help of a recently discovered natural mechanism for turning off genes.

I N F O R M A T I O N T E C H N O L O G Y

42 Demystifying the Digital DivideB Y M A R K W A R S C H A U E RHanding out computers and Internet access is the wrong way to raise technological literacy.

N E U R O S C I E N C E

50 Rethinking the “Lesser Brain”B Y J A M E S M . B O W E R A N D L A W R E N C E M . P A R S O N SThe cerebellum does more than coordinate body movement. It also weaves together signals from the senses.

P H Y S I C S

58 Information in the Holographic UniverseB Y J A C O B D . B E K E N S T E I NTheoretical work on black holes suggests that there are limits to how densely information can be packed—and that our universe might be like a giant hologram.

A R C H A E O L O G Y

66 Questioning the Delphic OracleB Y J O H N R . H A L E , J E L L E Z E I L I N G A D E B O E R , J E F F R E Y P . C H A N T O N A N D H E N R Y A . S P I L L E RThe ancient Greeks were right: vapors from the earth inspired the seer’s prophetic trances.

E V O L U T I O N

74 Planet of the ApesB Y D A V I D R . B E G U NThe Old World was home to as many as 100 species of apes, and those that gave rise to us may not have lived in Africa after all.

contentsaugust 2003

SCIENTIFIC AMERICAN Volume 289 Number 2 features

66 Mystery of the oracle solved


21

8 S C I E N T I F I C A M E R I C A N A U G U S T 2 0 0 3

departments10 SA Perspectives

Making space safe from the ground up.

12 How to Contact Us12 On the Web14 Letters18 50, 100 & 150 Years Ago20 News Scan

■ Global warming in the Middle Ages.■ VIRGO searches for gravity waves.■ Labeling “inert” ingredients in pesticides.■ Next stop, the earth’s core.■ Rooting Homo sapiens in Africa.■ By the Numbers: Future power shortages.■ Data Points: Video games enhance

visual processing.

30 InnovationsGrabbing particles with light leads to a new form of nanomanufacturing.

32 Staking ClaimsA sour remedy for treating angina, and more odd patents.

84 InsightsDoubters scoff, but asteroid watcher Brian Marsdenwatches for Armageddon from the skies.

86 Working KnowledgeSeeing in the dark.

88 Technicalities New devices connect the stereo and TV to the home data network.

91 ReviewsA Traveler’s Guide to Mars makes the case that the Red Planet remains geologically active.

84Brian Marsden, Smithsonian Astrophysical Observatory

88

SCIENTIFIC AMERICAN Volume 289 Number 2

columns33 Skeptic B Y M I C H A E L S H E R M E R

The ignoble savage.

93 Puzzling Adventures B Y D E N N I S E . S H A S H AOutwitting spies.

94 Anti Gravity B Y S T E V E M I R S K YTruth in science news.

95 Ask the Experts Would you fall all the way through a hole in the earth? How are calories counted?

96 Fuzzy Logic B Y R O Z C H A S T

Cover image by Kenn Brown; photograph by Sanjay Kothari and imaging by Trucollage (page 5)

Scientific American (ISSN 0036-8733), published monthly by Scientific American, Inc., 415 Madison Avenue, New York, N.Y. 10017-1111. Copyright © 2003 by ScientificAmerican, Inc. All rights reserved. No part of this issue may be reproduced by any mechanical, photographic or electronic process, or in the form of a phonographic recording,nor may it be stored in a retrieval system, transmitted or otherwise copied for public or private use without written permission of the publisher. Periodicals postage paid at NewYork, N.Y., and at additional mailing offices. Canada Post International Publications Mail (Canadian Distribution) Sales Agreement No. 242764. Canadian BN No. 127387652RT;QST No. Q1015332537. Subscription rates: one year $34.97, Canada $49 USD, International $55 USD. Postmaster: Send address changes to Scientific American, Box 3187,Harlan, Iowa 51537. Reprints available: write Reprint Department, Scientific American, Inc., 415 Madison Avenue, New York, N.Y. 10017-1111; (212) 451-8877;fax: (212) 355-0408 or send e-mail to [email protected] Subscription inquiries: U.S. and Canada (800) 333-1199; other (515) 247-7631. Printed in U.S.A.


In retrospect, the missteps that led to the loss of thespace shuttle Columbia seem so obvious. In every oneof the 113 shuttle flights since the program began in1981, small pieces of insulation foam peeled off the ve-hicle’s external tank during launch and dinged the or-biter. In at least eight flights, larger hunks of foam de-tached from the bipod ramps (the insulation coveringthe areas where struts attach the external tank to the

orbiter). During the launch of theshuttle Atlantis last October, afoot-long chunk fell from a bipodramp and hit one of the solid-fuelboosters. But in the Flight Readi-ness Review for the next shuttlemission, NASA managers con-cluded that the foam strikes didnot pose a threat. Instead of thor-oughly analyzing the problem,they put out a perfunctory ratio-nale including statements such as“Ramp foam application in-volves craftsmanship” and “Allramp closeout work was per-

formed by experienced practitioners.”One minute and 21 seconds into Columbia’s final

launch on January 16, a briefcase-size piece of foamseparated from the bipod area and slammed into theorbiter’s left wing at more than 500 miles an hour. Ac-cording to the Columbia Accident Investigation Board,which is due to release its report this summer, the im-pact most likely opened a breach in the wing’s leadingedge. On February 1, when the the shuttle reenteredthe atmosphere, superheated gases jetted through thehole like a blowtorch.

Hindsight is 20/20, of course. How could anyonehave known that a routine problem that had causedonly nicks to the orbiter in 112 flights would do lethal

damage in the 113th? But this wasn’t the first time thatNASA failed to recognize the dangers of a routineanomaly. In several shuttle flights during the mid-1980s, engineers had noticed an ominous sign—par-tial erosion of the O-rings in the solid-fuel boosters—

but nobody heeded their warnings. After an O-ringleak caused the explosion of Challenger in 1986, NASA

revamped its procedure for launch decisions to involvemore engineers and safety experts. Events during theColumbia flight, however, showed that the spaceagency still hadn’t learned how to listen to the cautionsof its own personnel. When NASA engineers asked theNational Imagery and Mapping Agency to take satel-lite photographs of the shuttle to look for damage fromthe foam impact, their superiors overruled the request.

To do justice to the seven astronauts killed in theColumbia accident, NASA must go far beyond techni-cal fixes to the bipod area. Before the space shuttles areallowed to fly again, the agency must restructure itsmission teams so that engineers and safety experts havesufficient resources to fully investigate flight anomaliesand enough independent clout to challenge programadministrators. In testimony before Congress in May,Harold W. Gehman, Jr., the retired admiral who headsthe accident investigation board, observed that NASA

engineers cannot persuade the agency to focus on asafety problem unless they have hard data to back uptheir concerns. Noted Gehman: “The people whowould say, ‘Wait a minute, this is not safe,’ can’t comeargue their cases with 18 inches worth of documenta-tion, because they aren’t funded well enough.”

Given the inherent risks of spaceflight and the un-gainly design of the shuttle, NASA may not be able tobar a third catastrophe (especially if it keeps the agingshuttles flying until 2015 or longer). But the agency canreduce the chances of another accident in space by im-proving its communications on the ground.


NAS

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SA Perspectives

THE EDITORS [email protected]

Houston, You Have a Problem

COLUMBIA ASTRONAUTS KalpanaChawla and Rick Husbandshortly before the accident.



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Sci/Tech Web Awards 2003It’s a jungle out there. With morethan three billion Web pages to siftthrough, finding great science sitesis harder than ever. The good newsis that the editors at Scientific American have once againtrawled the Internet for the best the Web has to offer. Wethink our list of winners has something for everyone.

Gecko-Inspired Adhesive Sticks It to Traditional TapeMove over, Spider-Man—

soon the rest of us may be able to scale walls and cling to ceilings, too. Researchers have developed a supersticky adhesive modeledon the gecko foot that grips even the slipperiest surface. So tenacious is this gecko tape, they report, that it could suspend a person from the ceiling by one hand.

Ask the ExpertsWhat causes stuttering?Speech-language pathologist Luc F. De Nilof the University of Toronto explains.

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REALITY CHECK“Get Real” [Perspectives] derides oppo-nents of technologies such as cloning as“technocynics,” as if they were irra-tionally antitechnology and antiprogress.Perhaps some are driven by such fears,but many are also dedicated scientistsand engineers with solid credentials, suc-cessful careers and a deep love for the val-ue of their work. Objecting to how closewe are to crossing the line with regard tocreating or destroying human life isn’t ablanket condemnation of technology.

Who’s being hurt in therapeuticcloning? Well, for one, the individualwhose life-building stem cells are har-vested for use by others. It’s tragic ironyfor you to brush aside warnings aboutdegrading human life, because the cal-lous and flippant attitude expressed inyour column reveals that you’ve alreadycrossed that line of dehumanization inyour own hearts, and you seem either notto know or not to care. While we unceas-ingly pursue answers to the whats andhows of nature and existence, we must re-member to keep seeking the whys as well.

Michael KonopikMenlo Park, Calif.

Your editorial completely ignores a ma-jor point that critics make: much scienceand technological development is fundedand controlled by corporations and gov-ernment—entities that may be concernedwith accumulating profits and enhancingpower at the expense of ordinary people.The editorial also brushes off the notion

that people lack the ability to managerapid scientific and technological ad-vances. Consider: we are in the midst ofan extinction crisis resulting from humanpopulation growth and increases in con-sumption made possible by modern sci-ence and technology; the list of Super-fund sites is growing; policy to counterglobal warming remains ineffective.

When Richard Gatling invented themachine gun, he thought it would endwar because no one would be foolishenough to charge the weapon, nor wouldanyone be so inhumane as to actually useit. Many citizens and scientists recognizethat nothing is more dangerous to our-selves and the rest of life than hubris.

David M. JohnsMcMinnville, Ore.

On the whole, your balanced view oftechnology seems appropriate. Whenyou suggest that to stop research is togive up trying to make the world a betterplace, however, you tend to promote yourown dangerous extreme. Often technolo-gy is used to “fix” something that is re-ally a symptom of a more fundamentalsystemic dysfunction. Worse, because ofthe complexities of human and ecologi-cal systems, the fixes often have unin-tended negative consequences. Unfortu-nately, those problems are usually met,because of the prevalent mind-set, withmerely another technofix.

Technology provides useful tools, butit is not the ultimate answer to making theworld a better place. For that, we require


TECHNOLOGY, IT IS OFTEN SAID, is “neutral,” neither goodnor bad—a tool whose function is determined by the peoplewho control it. Except when it isn’t. That was the reaction ofseveral readers to the April editorial “Get Real” [Perspectives].The editors warned against “technocynics” who may impedethe progress of various promising lines of research—includingtherapeutic cloning and genetically modified foods—based on“abstract worries” about the vague possibility of “doing moreharm than good.” Some correspondents urged that researchshould respect differing views on what is damaging, especial-ly regarding precious human life. Critics and defenders of sci-ence face off below on this and other topics from the April issue.

LettersE D I T O R S @ S C I A M . C O M

E D I T O R I N C H I E F : John Rennie E X E C U T I V E E D I T O R : Mariette DiChristina M A N A G I N G E D I T O R : Ricki L. Rusting N E W S E D I T O R : Philip M. Yam S P E C I A L P R O J E C T S E D I T O R : Gary Stix S E N I O R E D I T O R : Michelle Press S E N I O R W R I T E R : W. Wayt Gibbs E D I T O R S : Mark Alpert, Steven Ashley, Graham P. Collins, Carol Ezzell, Steve Mirsky, George Musser C O N T R I B U T I N G E D I T O R S : Mark Fischetti, Marguerite Holloway, Michael Shermer, Sarah Simpson, Paul Wallich

E D I T O R I A L D I R E C T O R , O N L I N E : Kate Wong A S S O C I A T E E D I T O R , O N L I N E : Sarah Graham

A R T D I R E C T O R : Edward Bell S E N I O R A S S O C I A T E A R T D I R E C T O R : Jana Brenning A S S I S T A N T A R T D I R E C T O R S :Johnny Johnson, Mark Clemens P H O T O G R A P H Y E D I T O R : Bridget Gerety P R O D U C T I O N E D I T O R : Richard Hunt

C O P Y D I R E C T O R : Maria-Christina Keller C O P Y C H I E F : Molly K. Frances C O P Y A N D R E S E A R C H : Daniel C. Schlenoff, Rina Bander, Emily Harrison

E D I T O R I A L A D M I N I S T R A T O R : Jacob Lasky S E N I O R S E C R E T A R Y : Maya Harty

A S S O C I A T E P U B L I S H E R , P R O D U C T I O N : William Sherman M A N U F A C T U R I N G M A N A G E R : Janet Cermak A D V E R T I S I N G P R O D U C T I O N M A N A G E R : Carl Cherebin P R E P R E S S A N D Q U A L I T Y M A N A G E R : Silvia Di Placido P R I N T P R O D U C T I O N M A N A G E R : Georgina Franco P R O D U C T I O N M A N A G E R : Christina Hippeli C U S T O M P U B L I S H I N G M A N A G E R : Madelyn Keyes-Milch

A S S O C I A T E P U B L I S H E R / V I C E P R E S I D E N T , C I R C U L A T I O N :Lorraine Leib Terlecki C I R C U L A T I O N D I R E C T O R : Katherine Corvino C I R C U L A T I O N P R O M O T I O N M A N A G E R : Joanne Guralnick F U L F I L L M E N T A N D D I S T R I B U T I O N M A N A G E R : Rosa Davis

V I C E P R E S I D E N T A N D P U B L I S H E R : Bruce Brandfon A S S O C I A T E P U B L I S H E R : Gail Delott S A L E S D E V E L O P M E N T M A N A G E R : David Tirpack SALES REPRESENTATIVES: Stephen Dudley, Hunter Millington, Stan Schmidt, Debra Silver

ASSOCIATE PUBLISHER, STRATEGIC PLANNING: Laura Salant P R O M O T I O N M A N A G E R : Diane Schube R E S E A R C H M A N A G E R : Aida Dadurian P R O M O T I O N D E S I G N M A N A G E R : Nancy Mongelli G E N E R A L M A N A G E R : Michael Florek B U S I N E S S M A N A G E R : Marie Maher M A N A G E R , A D V E R T I S I N G A C C O U N T I N G A N D C O O R D I N A T I O N : Constance Holmes

D I R E C T O R , S P E C I A L P R O J E C T S : Barth David Schwartz

M A N A G I N G D I R E C T O R , O N L I N E : Mina C. Lux S A L E S R E P R E S E N T A T I V E , O N L I N E : Gary BronsonW E B D E S I G N M A N A G E R : Ryan Reid

D I R E C T O R , A N C I L L A R Y P R O D U C T S : Diane McGarvey P E R M I S S I O N S M A N A G E R : Linda Hertz M A N A G E R O F C U S T O M P U B L I S H I N G : Jeremy A. Abbate

C H A I R M A N E M E R I T U S : John J. Hanley C H A I R M A N : Rolf Grisebach P R E S I D E N T A N D C H I E F E X E C U T I V E O F F I C E R :Gretchen G. Teichgraeber V I C E P R E S I D E N T A N D M A N A G I N G D I R E C T O R ,I N T E R N A T I O N A L : Dean SandersonV I C E P R E S I D E N T : Frances Newburg

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a paradigm shift into a systems- and com-plexity-science-based way of thinking.

Mark S. MerittRed Hook, N.Y.

Your editorial suggests that those whoare wary of genetically modified (GM)foods bemoan all new science and tech-nology. In fact, the opposite is true. GMfoods may yet be the solution to theworld’s hunger problems, but evidence in-dicates that their genes transfer into otherorganisms and that the effect on humanhealth may be less than positive. Do we re-ally want weed- or pest-resistance genes inGM crops spreading to native plants? Asfor human health, the FDA requires exten-sive testing of new drugs; these molecules,once approved, are administered only tothose with a medical need, usually for lim-ited periods and under the watchful eye ofa physician. On the other hand, GM foodsmay be eaten by everyone, unmonitored,for the rest of their life.

Science could address the related ques-tions, and I’d be delighted if the answercame back: “After extensive testing, ithas been concluded that GM organismsdo not harm humans or the environmenton which they depend.” But that wouldtake more science, not less.

Stephanie FergusonIndianapolis

In support of your editorial highlightingsome of the illogical and sensationalistviews of technocynics, I would like to addmore fuel for debate. The association ofGM food with Frankensteinian images isirrational. Humans have been eating ge-netically altered food for hundreds oreven thousands of years, since the intro-duction of agriculture. Although it is pos-sible that food that is genetically modifiedin certain ways could be deleterious to thehealth of consumers, such as by the in-troduction of carcinogens, the mere factthat a food is genetically modified shouldnot be regarded as something alien orharmful. Public education led by scientistsis required to avoid the further develop-ment of a culture of antiscience and to

break down the stigma associated withGM food.

Paul K. WrightUniversity Hospital of North Durham

Durham, England

HERBAL CAUTIONI just finished “The Lowdown on Gink-go Biloba,” by Paul E. Gold, Larry Cahilland Gary L. Wenk. One thing that wasnot stressed is that people who take sup-plements need to inform their health careproviders.

Many supplements cause no harm(except perhaps to the pocketbook), andsome are beneficial but still may not mix

well with conventional medications. Anexcellent reference is the Natural Medi-cines Comprehensive Database (www.naturaldatabase.com), a pay site that ex-plains what herbals are used for, whatthey are safe (or unsafe) for and how theyinteract with various drugs.

David M. Jonesvia e-mail

A GRID’S UTILITYIan Foster’s article “The Grid: Comput-ing without Bounds” fantastically inflatedan interesting software project, Globus,into the certainty of computing as a gen-eral utility. Bandwidth is an item the user

cannot readily produce, so it is reasonableto make a utility using it. Not so for pro-cessing and storage. The computing pow-er of yesteryear’s huge mainframes drivestoday’s desktop word processing andgames of solitaire. Storage costs $1 a giga-byte. It’s not economically sensible to turnthings that are essentially free into a utili-ty, as the article proposes.

Which brings me to the second point:bandwidth is not free. Foster provides nodiscussion of the economic impact of thebandwidth necessary to realize his vision.The price of transporting computer pro-cessing and storage cannot compete withthe low cost of keeping both local.

In the business world, grid computingis a solution without a problem.

L. L. WilliamsManitou Springs, Colo.

I had difficulty getting excited about gridcomputing, having experienced the slow,frustrating reality of wide-area distributednetworks. The total economic penalty ofthis inefficiency must be enormous.

Bruce VarleyMelville, Western Australia

ERRATA The News Scan story “Ma’s Eyes, NotHer Ways,” by Carol Ezzell, should have notedthat the cloned pigs were created at TexasA&M University by Shawn Walker and Jorge A.Piedrahita (now at North Carolina State Uni-versity) and that they initiated the collabora-tion with Ted Friend and Greg Archer of TexasA&M, which resulted in the observation thatclones have differing physical and behavioralattributes. Cloned pig siblings in the study hadvarying numbers of teats, not teeth, as statedin the article.

Simulations in a pressure chamber thatmimics conditions on the sunken oil tankerPrestige achieved about 350 atmospheres,not 100 [“Oiling Up Spain,” by Luis MiguelAriza, News Scan].

Ray Davis was a scientist in the chemistrydepartment at Brookhaven National Labora-tory when he did his pioneering work that be-gan the field of solar neutrino research [“Solv-ing the Solar Neutrino Problem,” by Arthur B.McDonald, Joshua R. Klein and David L. Wark].


LettersLetters

GINKGO and other herbs may interact with drugs.

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AUGUST 1953CONTRACEPTION—“Research on contra-ception by physiological rather than me-chanical methods is making considerableprogress, according to a recent report inScience by Paul Henshaw of the PlannedParenthood Foundation. The studies havetwo objectives: to improve the fertility ofchildless couples, and to develop a reli-able and convenient form of contracep-tion by pill, injection, timing or a combi-nation of these methods.”

BETTER SOIL ... MAYBE—“Somehail the new soil conditionersas wonder chemicals which,sprinkled on the ground, turnclay or sand to rich, loose top-soil in a few hours, removingall need for organic matterand the back-breaking laborof digging and cultivating.Chemically they are long-chainpolymers. Functionally theirmolecular charges attract clayparticles in the soil like a magnet, forming many smalllumps or aggregates. The Con-necticut Agricultural Experi-ment Station ran some testsand it was found that if thechemicals are put down in ex-cessive amounts, they retardgermination and repress plantgrowth. Being essentially plas-tics, the conditioners literallyplasticized the soil. However, some testshave shown increased yields.”

AUGUST 1903E.T. ISN’T PHONING—“On Mars, whenthe planet comes into favorable positionfor observation, astronomers are able tosee one or more irregular bright projec-tions on the sunrise or sunset line. Thenature of these projections is pretty wellunderstood by astronomers, but the bi-ennial press reports of such sightings giverise to a question on the part of the pub-

lic as to whether they could be signalsfrom intelligent beings on that planet. Allthe observed phenomena can be satisfac-torily accounted for on the theory that theprojections are due to clouds of consid-erable size, at great elevations in the rar-efied atmosphere. Such clouds would beilluminated by the sun’s rays while theland areas beneath them were still so darkas to form a black background. —W. W.Campbell, Director, Lick Observatory”

THE NEW CHEMISTRY—“Just what shallbe done with the newly discovered radio-active substances is a problem that per-plexes every thinking physicist. Theyrefuse to fit into our established and har-monious chemical system; they eventhreaten to undermine the venerableatomic theory, which we have acceptedunquestioned for well-nigh a century.The elements, once conceived to be sim-ple forms of primordial matter, are bold-ly proclaimed to be minute astronomicalsystems of whirling units of matter. This

seems more like scientific moonshinethan sober thought; and yet the new doc-trines are accepted by Sir Oliver Lodgeand by Lord Kelvin himself.”

ELECTRICITY FOR LIGHT—“Our illustra-tion shows a searchlight made by the firmof Schuckert & Co., in Nuremberg, Ger-many, with an Iris shutter, half closed,which has a diameter of 6 feet 6 inchesand throws a beam of light of 316 million

candle power. Searchlightssuch as this are destined to re-place the old petroleum lightsthat so long flashed out theirdanger signals to marinersfrom lighthouses.”

AUGUST 1853WEATHER BALLOONIST—“Mr.John Wise, the celebrated aer-ial navigator of nearly twohundred atmospheric voy-ages, writes to us: ‘In your ar-ticle on the subject of Thunderand Lightning you say you“have come to the conclusionthat for one vertical flash oflightning that reaches theearth, fifty are horizontal—dissipating in the atmospherelike the fibres of a vine spread-ing out from the main trunk.”I think you are correct in yourconclusion; the dissipationtakes place in the lower cloud

surface. I have witnessed the same thingwhen sailing above the layer of cloudsduring thunder storms.’”

PESTILENCE AT HOME—“The city of NewOrleans is severely afflicted with yellowfever this summer. No less than 200 havedied in one day.”

PESTILENCE ABROAD—“The cholera isnow raging fearfully in some places ofDenmark. In Copenhagen, 300 died of itin one day.”


Fixing Dirt ■ Atomic Revision ■ Epidemic News

50, 100 & 150 Years AgoFROM SCIENTIFIC AMERICAN

316 MILLION ELECTRIC CANDLES—for lighthouses, 1903



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In a contretemps indicative of the politicalstruggle over global climate change, a re-cent study suggested that humans may not

be warming the earth. Greenhouse skeptics,pro-industry groups and political conserva-tives have seized on the results, proclaimingthat the science of climate change is incon-clusive and that agreements such as the Kyo-to Protocol, which set limits on the output ofindustrial heat-trapping gases, are unneces-sary. But mainstream climatologists, as rep-resented by the Intergovernmental Panel on

Climate Change (IPCC), are perturbed thatthe report has received so much attention;they say the study’s conclusions are scientifi-cally dubious and colored by politics.

Sallie Baliunas and Willie Soon of the Har-vard-Smithsonian Center for Astrophysics re-viewed more than 200 studies that examinedclimate “proxy” records—data from suchphenomena as the growth of tree rings orcoral, which are sensitive to climatic condi-tions. They concluded in the January ClimateResearch that “across the world, manyrecords reveal that the 20th century is proba-bly not the warmest nor a uniquely extremeclimate period of the last millennium.” Theysaid that two extreme climate periods—theMedieval Warming Period between 800 and1300 and the Little Ice Age of 1300 to 1900—

occurred worldwide, at a time before indus-trial emissions of greenhouse gases becameabundant. (A longer version subsequently ap-peared in the May Energy and Environment.)

In contrast, the consensus view among pa-leoclimatologists is that the Medieval Warm-ing Period was regional, that the worldwidenature of the Little Ice Age is open to questionand that the late 20th century saw the mostextreme global average temperatures.

Scientists skeptical of human-inducedwarming applaud the analysis by Soon andBaliunas. “It has been painstaking and metic-ulous,” says William Kininmonth, a meteoro-

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Hot WordsA CLAIM OF NONHUMAN-INDUCED GLOBAL WARMING SPARKS DEBATE BY DAVID APPELL

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TREE RINGS hold clues about past climate, because temperature affects a tree’s growth.


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Mainstream climatologistsperceive flaws in a paper by WillieSoon and Sallie Baliunas, the twoHarvard-Smithsonian researcherswho produced results skeptical ofhuman-induced global warming.Some conclude that politics drovethe paper’s publication in ClimateResearch. One of the journal’seditors, Chris de Freitas of theUniversity of Auckland, hasfrequently editorialized in the NewZealand press against theoverwhelmingly acceptedconclusions of the IPCC. And atleast three scientists who were onthe journal’s peer-review panel—Wolfgang Cramer, Tom Wigley andDanny Harvey—have complainedthat de Freitas has published papersthey have deemed unacceptablewithout notifying them.

Wigley says that such action isvery unusual; de Freitas respondsthat he “was not too concerned[about Wigley’s complaint] asperiodically I receive diametricallyopposed assessments fromexperts,” especially, he says, “asthe work in question was a criticalassessment of Wigley’s own work.”

The Soon and Baliunas paperproduced political results in onerespect: it seems to haveemboldened the Bushadministration to edit a JuneEnvironmental Protection Agencyreport so that it no longerrepresented a scientificconsensus about climate change.The New York Times reported that,as a result, the EPA decided topublish much weaker statementsabout global warming.

logical consultant in Kew, Australia, and for-mer head of the Australian National ClimateCenter. But he says that “from a purely sta-tistical viewpoint, the work can be criticized.”

And that criticism, from many scientistswho feel that Soon and Baliunas produceddeeply flawed work, has been unusually stri-dent. “The fact that it has received any atten-tion at all is a result, again in my view, of itsutility to those groups who want the globalwarming issue to just go away,” commentsTim Barnett, a marine physicist at the ScrippsInstitution of Oceanography, whose workSoon and Baliunas refer to. Similar sentimentscame from Malcolm Hughes of the Labora-tory of Tree-Ring Research at the Universityof Arizona, whose work is also discussed:“The Soon et al. paper is so fundamentallymisconceived and contains so many egregiouserrors that it would take weeks to list and ex-plain them all.”

Rather than seeing global anomalies,many paleoclimatologists subscribe to theconclusions of Phil Jones of the University ofEast Anglia, Michael Mann of the Universityof Virginia and their colleagues, who beganin 1998 to quantitatively splice together theproxy records. They have concluded that theglobal average temperature over the past1,000 years has been relatively stable until the20th century. “Nothing in the paper under-mines in any way the conclusion of earlierstudies that the average temperature of thelate twentieth century in the Northern Hemi-sphere was anomalous against the back-ground of the past millennium,” wrote Mannand Princeton University’s Michael Oppen-heimer in a privately circulated statement.

The most significant criticism is that Soonand Baliunas do not present their data quan-titatively—instead they merely categorize thework of others primarily into one of two sets:either supporting or not supporting their par-ticular definitions of a Medieval Warming Pe-riod or Little Ice Age. “I was stating outrightthat I’m not able to give too many quantita-tive details, especially in terms of aggregatingall the results,” Soon says.

Specifically, they define a “climatic anom-aly” as a period of 50 or more years of wet-ness or dryness or sustained warmth (or, forthe Little Ice Age, coolness). The problem isthat under this broad definition a wet or dryspell would indicate a climatic anomaly evenif the temperature remained perfectly con-

stant. Soon and Baliunas are “mindful” thatthe Medieval Warming Period and the LittleIce Age should be defined by temperature, but“we emphasize that great bias would result ifthose thermal anomalies were to be dissociat-ed” from other climatic conditions. (Asked todefine “wetness” and “dryness,” Soon andBaliunas say only that they “referred to thestandard usage in English.”)

What is more, their results were nonsyn-chronous: “Their analysis doesn’t considerwhether the warm/cold periods occurred atthe same time,” says Peter Stott, a climate sci-entist at the U.K.’s Hadley Center for Climate

Prediction and Research in Bracknell. For ex-ample, if a proxy record indicated that a dri-er condition existed in one part of the worldfrom 800 to 850, it would be counted as equalevidence for a Medieval Warming Period asa different proxy record that showed wetterconditions in another part of the world from1250 to 1300. Regional conditions do notnecessarily mirror the global average, Stottnotes: “Iceland and Greenland had theirwarmest periods in the 1930s, whereas thewarmest for the globe was the 1990s.”

Soon and Baliunas also take issue with theIPCC by contending that the 20th centurysaw no unique patterns: they found few cli-matic anomalies in the proxy records. Butthey looked for 50-year-long anomalies; thelast century’s warming, the IPCC concludes,occurred in two periods of about 30 yearseach (with cooling in between). The warmestperiod occurred in the late 20th century—tooshort to meet Soon and Baliunas’s selected re-quirement. The two researchers also discountthermometer readings and “give great weightto the paleo data for which the uncertaintiesare much greater,” Stott says.

The conclusion of Soon and Baliunas that

CORAL can serve as climate proxy records: theirchemical makeup depends on temperature and salinity.

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Spraying for mosquitoes has increasing-ly become a summer routine in manyareas, thanks to the West Nile virus.

Residents who want to find out what’s beingsprayed could turn to the product label on thecontainer. But even a thorough reading of the

label won’t tell the whole story. Most “inert”ingredients, which often constitute up to 99percent of the product contents, are not list-ed. Yet they can be biochemically active—forexample, an unlisted ingredient in the mos-quito pesticide Dibrom is naphthalene, whichmight cause cancer and developmental prob-lems in exposed children. Now some activistsare trying to get the Environmental Protec-tion Agency to force chemical makers into re-vealing their hidden compounds.

According to the Federal Insecticide,Fungicide and Rodenticide Act, pesticide in-gredients qualify as inert when their functionin a product is something other than killingthe target pest. For instance, an inert maymake a product sticky, or sprayable, or at-tractive to a particular kind of bug or rodent.Yet the term “inert” does not bear on the

toxicity of the ingredient to other organisms. In the case of Monsanto’s product Round-

up, currently the most used herbicide in theworld, a Texas Tech University study pub-lished in 2000 revealed a 90 percent decreasein the production of certain reproductive hor-mones in exposed mice. After the researchersgave mice glyphosate, the only listed activeingredient in Roundup, they did not see thedecrease in hormone production. They con-cluded that the inert ingredients in the prod-uct caused the reduced sexual hormones.

In March 2000 the EPA brought togetherpublic-interest groups and pesticide manu-facturers for a workshop to discuss ways toenhance disclosure of inert ingredients to con-sumers and to emergency health profession-als, who can be ill equipped to treat exposuresymptoms if they cannot identify the culpritchemical. Since 1987, pesticide manufacturershave had to register all their ingredients withthe EPA, but most inerts are protected frompublic disclosure as trade secrets. The EPA ini-tiative categorized the compounds into fourlists and pushed for further toxicity testing.

More than half of all EPA-registered in-erts fall into List 3: “inerts of unknown tox-icity.” And according to a survey by theNorthwest Coalition for Alternatives to Pes-ticides (NCAP) in Eugene, Ore., about a quar-ter of inert substances, many on List 3, arealready classified as hazardous under theClean Air Act, the Safe Drinking Water Actand other federal statutes.

Industry representatives argue that fulldisclosure of inerts would cause manufactur-ers severe competitive harm. “It basicallywould tear down the art we’ve practiced and

the warming during the 20th century is not un-usual has engendered sharp debate and intensereactions on both sides—Soon and Baliunas re-sponded primarily via e-mail and refused fol-low-up questions. The charges illustrate the po-larized nature of the climate change debate inthe U.S. “You’d be challenged, I’d bet, to findsomeone who supports the Kyoto Protocol and

also thinks that this paper is good science, orsomeone who thinks that the paper is bad sci-ence and is opposed to Kyoto,” predicts RogerPielke, Jr., of the University of Colorado. Ex-pect more of such flares as the stakes—and theworld’s temperatures—continue to rise.

David Appell is based in Lee, N.H.

Secret Ingredients“INERT” COMPOUNDS MAY BE CHEMICALLY ACTIVE—AND TOXIC BY DAVID J. EPSTEIN

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Pesticides contain many kinds ofchemicals labeled as inert. The EPA

places them into four categories; a few examples are listed (see

www.epa.gov/opprd001/inerts/lists.html).

List 1 (“of toxicological concern”; 7 compounds):

Phenol, hydroquinone

List 2 (“potentially toxic”; 95 compounds):

Diesel fuel, nitromethane, certainpetroleum distillates, toluene

List 3 (“of unknown toxicity”; about 2,000 compounds):

Asphalt, atropine, borax, coal tar,dried blood, formaldehyde,

hydrogen peroxide, kerosene,naphthalene, propane, shellac,

sulfuric acid, turpentine, tobacco dust

List 4 (“of minimal concern”; more than 1,000 compounds):Beer, egg white, oyster shells,paprika, polyurethane, spermwhale oil, sugar, sulfur, yeast

AN END TOA BUG’S LIFE

PESTICIDE LABELS do not list the “inert” ingredients.



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F or more than a century, paleoanthro-pologists have been at loggerheads overthe origin of modern humans. Two fac-

tions occupy the forefront of the debate:those who subscribe to the Out of Africa the-ory, which holds that Homo sapiens arose inAfrica alone between 200,000 and 150,000years ago and subsequently spread across theglobe, replacing archaic hominids; and thosewho espouse the multiregional evolution the-ory, which proposes that modern humansemerged from archaic populations across theOld World.

The Out of Africa model has come out asthe clear favorite, bolstered by numerous ge-netic studies. Critics, however, have chargedthat fossil support for the theory is flimsy. IfAfrica was the fountainhead of modern hu-man morphology, then the first modern-looking fossils should come from that conti-nent. But a hole in the African fossil recordbetween 300,000 and 100,000 years ago,when the transition to morphological moder-nity is believed to have occurred, has pre-vented scientists from testing that prediction.

New finds from a site called Herto in

Ethiopia’s Middle Awash region bridge thatgap. In the June 12 Nature, Tim D. White ofthe University of California at Berkeley andhis colleagues describe three skulls reliablydated at nearly 160,000 years old that theysay represent the earliest near-modern hu-mans on record. The fossils, assigned to anew subspecies, H. sapiens idaltu, exhibitsuch modern traits as a globular braincase,but they also retain some ancient features—

a heavy browridge, for example. Their anato-my and antiquity, the researchers observe,link earlier archaic African forms to later ful-ly modern ones, thereby providing strong evidence that Africa was the birthplace ofour kind.

The Herto hominids also bear on anoth-er, related question: Namely, were Neander-tals among the forebears of living peoples?Whereas Out of Africa theorists contend thatsuch archaic hominids did not contribute sig-

just give it to our competitors globally whocan produce it at lower costs because ofcheaper labor and lower safety standards,”comments Chip Collins of Stepan, a firmbased in Northfield, Ill., that makes inerts fora variety of products, including pesticides.

NCAP and other public-interest represen-tatives maintain that the means to reverse-en-gineer pesticide formulations, which they argueis available to companies with well-equippedlabs, already renders inert identities reasonablyobtainable to competitors. Data about the in-erts should therefore be subject to Freedom ofInformation Act requests. In fact, throughsuch requests NCAP has obtained documen-tation from the EPA on inerts in hundreds ofproducts, but some requests “have been in thehopper since 1996,” NCAP’s Caroline Coxsays. Moreover, manufacturers retain theability to deny disclosure if they claim thatthey will suffer competitive harm.

During the workshop the EPA formally de-nied a petition by NCAP to mandate disclosureof all inert ingredients on pesticide labels. Yetearlier this year the EPA began a pilot programof “voluntary disclosure” to urge companiesto offer up more ingredient information todoctors and toxicologists, notes Cameo Smootof the EPA Office of Pesticide Programs. Still,Cox is skeptical of the success of voluntaryprograms. “Voluntary disclosure is the statusquo, so what’s the difference?” she asks.

So now NCAP has gone to court to forceEPA officials to recognize the petition for fulldisclosure. “My personal opinion is that theywill not take any action unless essentially theyhave to,” Cox adds. “The briefs have all beenfiled,” she says, “but we currently have noidea what the judge will rule.” Pesticide inertscould be destined to remain a public mystery.

David J. Epstein is based in New York City.

Sourcing SapiensNEW FOSSILS AND DNA TESTS GET TO THE ROOTS OF OUR SPECIES BY K ATE WONG

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ALMOST MODERN: 160,000-year-old skull from Ethiopiasuggests that our species stemmed from Africa (top).An artist’s reconstruction shows what the individualmight have looked like in life (bottom).

List 1 inerts are now required onproduct labels. One positive effectof this rule, according to theEnvironmental Protection Bureauat the New York State AttorneyGeneral’s office, is that severalmanufacturers decided to dropcertain inerts altogether ratherthan subject them to the rigoroustesting required to determine theirdegree of toxicity.

LABELSWITH LESS



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P our a few million tons of molten ironinto a modest crack in the planet’s sur-face, and the seething blob will burrow

some 3,000 kilometers down to the outercore in a matter of weeks. Plant a grapefruit-size probe inside the sinking metal, and youhave a sensational new way to explore theearth’s inner workings.

At least that’s how David J. Stevenson, aplanetary scientist at the California Instituteof Technology, envisions it. Some of Steven-son’s colleagues have laughed out loud at hismusings; others have called them “goofy.”But at least a few geophysicists admit that theidea is promising, even feasible.

“We don’t know that it wouldn’t work,”says earth scientist Paul J. Tackley of the Uni-versity of California at Los Angeles. And hesees plenty of reasons to launch such a journey.

What scientists currently know about theinner earth has been inferred indirectly—

from the way earthquake vibrations travelthrough the planet’s middle or from alteredbits of mantle rocks that are coughed up thethroats of volcanoes. Most researchers haveabandoned any hope of making direct obser-vations: drilling below about 12 kilometershas proved futile because of the intense pres-sures exerted by the overlying rock.

What makes Stevenson’s plan different isthat it requires no drilling. Instead the probe’sjourney begins with a crack, which would re-quire the equivalent of a few megatons of TNTto create. Once filled with 100,000 to 10 mil-lion metric tons of iron, the crack would growdownward. The sinking iron, with a densityabout twice that of the surrounding rock,would advance the crack because of the force

nificantly to the modern human gene pool,some multiregionalists have argued that theNeandertals independently evolved into mod-ern Europeans. The presence of near modernsin Africa while the Neandertals were still de-veloping their distinctive characteristics inEurope makes it highly unlikely that Nean-dertals were ancestral to modern humans,White’s team asserts.

Scientists working on ancient DNA havereached similar conclusions. In May, GiorgioBertorelle of the University of Ferrara in Italyand his colleagues reported that mitochon-drial DNA (mtDNA) sequences from twoearly modern European fossils differ marked-ly from the mtDNA sequences previously re-covered from four Neandertal specimens.They fall within the range of genetic variationseen in Europeans today, however.

Not everyone is convinced by the caseagainst Neandertal ancestry. Fred H. Smithof Loyola University of Chicago countersthat although the Herto finds add weight tothe idea that modern humans originated inAfrica, they do not address the question of

whether those moderns mingled with the ar-chaic hominids they encountered on leavingtheir homeland. Smith has argued that anumber of early modern European fossilspossess Neandertal traits, suggesting that thetwo groups interbred. Neither is Smith per-suaded by the DNA data. “Two individualsdo not tell us what the genetic makeup of ear-ly modern human populations was,” he re-marks. “We need a good deal more data todetermine whether Neandertals contributedgenetically to that population.”

Although disagreement over the origin ofmodern humans and the fate of the Nean-dertals and other ancient hominids persists,the dispute itself has evolved. “Continuityversus replacement is dead,” declares ErikTrinkaus of Washington University. The de-bate now is over “trivial amounts of admix-ture versus major amounts of admixture.”For his part, Trinkaus suspects that earlymodern humans and Neandertals paid littleattention to the physical differences betweenthem. “They saw each other as people,” hesurmises—and did what people do.

Deep ThoughtsHOW TO JOURNEY TO THE CENTER OF THE EARTH—MAYBE BY SARAH SIMPSON

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The Neandertal mitochondrial DNA(mtDNA) sequences published so

far have been found to differconsiderably from those of

contemporary Europeans, thussupporting the Out of Africa

proponents’ view that Neandertalsdid not contribute to the modern

gene pool. But someanthropologists complain that toensure that the sequences trulycome from Neandertals and not

modern contaminants, molecularbiologists typically accept as valid

only those sequences that lieoutside of the modern human

range. This requirement therebystacks the deck against

Neandertals that might have DNAlike ours, which is what thoseadvocating the multiregional

evolution theory expect to see.

NEED TO KNOW:NEANDERTAL DNA



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Sending a blob of molten iron deepinside the earth has spawned a fewthought experiments, if nothingelse. Burning enough fossil fuel tomelt the iron would surelyexacerbate global warming, saysPaul Johnson of the University ofWashington. To liquefy 10 millionmetric tons of iron, a blast furnacewould emit about a megaton ofcarbon dioxide—a small butsignificant percentage of theannual production of thegreenhouse gas worldwide. But ifthe plan really works, “it could bethe antidote to global warming,”Johnson muses. Riding to the coreinside molten metal could be thelong-elusive answer for how todispose safely of spent nuclearreactor rods, making the switchfrom coal-burning to nuclear powerplants more desirable.

SIDE EFFECTS ANDCORE CONCERNS

H igh on any astrophysicist’s wish listis the detection of gravitational waves,ripples of spacetime caused by such vi-

olent phenomena as supernova and mergingblack holes. Researchers are pinning theirhopes on kilometer-long detectors. Theworld’s biggest, the $371-million Laser In-

terferometer Gravitational Observatory(LIGO), began taking data last year. Thispast July a French-Italian collaboration in-augurated VIRGO, which, though secondfiddle in size to LIGO, may be in a better po-sition to register the tiny, elusive wrinkles.And costing about 75 million euros (rough-

of gravity—like an ax splitting a log. Pressureof up to about 135 gigapascals—or 20 mil-lion pounds per square inch—within themantle would reseal the crack above.

Controlling the shape of the crack wouldbe more difficult, Tackley cautions. Naturalfractures might divert some of the iron fromits intended path. Tackley and Paul Johnson,a geophysicist at the University of Washing-ton, also point out that at least some of theiron would freeze as it descended through therelatively cold environs of the deep crust.

Overcoming the engineering difficultiesmay require melting much more iron thanwould ever be reasonable, Stevenson con-

cedes. Even more uncertain, he says, are thetime and money required to invent a probethat could survive the tortures of the trip (per-haps with electronics crafted from diamonds)

while successfully communicating itsfindings (probably via low-intensitysound waves) to researchers above.

“I suspect the actual cost of a proj-ect of this sort would make even NASA

blush,” Johnson speculates. But he addsthat while it’s easy to be a naysayerabout any of a dozen aspects of this plan(cracking the earth’s crust would prob-ably require nuclear explosions) theproposal’s greatest value is getting peo-ple to talk in new ways about a scientif-ic dream long since rejected by most.

Stevenson admits that although theideas had been bouncing around in hishead for a decade, it took him only sixhours to write them up—spurred on inpart by Paramount Pictures’s recent re-lease of its geophysical thriller, The Core.

Though not passionately commit-ted to realizing his scheme, Stevensonhopes that his fellow scientists will seehis proposal’s serious side. In the past

40 years, NASA has spent more than $10 bil-lion on unmanned exploration of space.Stevenson thinks our home planet is worth acomparable investment—a rather audaciousmessage coming from someone whose suc-cessful, 30-year career has been financedlargely by NASA.

“Knowing the composition and tempera-ture of the mantle and core is fundamental tounderstanding the origin of the earth,” he says.“We will never know if we don’t go there.”

View from VIRGOA NEW GRAVITY OBSERVATORY COMES ONLINE BY ALEX ANDER HELLEMANS

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GOING DOWN: A few million tons of molten iron would envelopa small probe. As the molten mass sank toward the core, theprobe would relay temperature and composition readings tothe surface via sound vibrations. (Diagram not to scale.)

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newsSCAN ly $87 million), it is substantially cheaper.

Like LIGO, VIRGO is a so-called Michel-son interferometer: light from a laser passesa beam splitter and travels down two per-pendicular evacuated pipes. The beams arereflected back by mirrors at the end of thepipes and “interfere” with each other. Specif-ically, they recombine destructively—that is,the waves cancel each other out. Any slightchange in arrival time (phase) gives itselfaway as a faint beam that can be detected byan optical sensor.

The LIGO interferometer arms are fourkilometers long; VIRGO’s arms extend threekilometers. Both are effectively much longerbecause the beams bounce back and forthdozens of times. Over these distances, the dis-tortions of space are approximately a bil-lionth the size of an atom—sufficient to causenoticeable differences in the phase of thecombining light beams. The challenge so farhas been boosting the detectors’ sensitivity:vibrations in the mirrors can obscure the tinysignals.

Seismicity is a major problem for LIGO[see “Ripples in Spacetime,” by W. WaytGibbs; Scientific American, April 2002].It limits the detection of signals below 60hertz, where astrophysicists have more con-fidence in what a gravitational signal shouldlook like and where the strongest signals areexpected to be.

VIRGO includes seismic isolators forevery optical component in the interferome-ter. Each “superattenuator” comprises sixsets of coupled springs and weights housed ina 10-meter-tall tower. The weights act likependulums, damping horizontal swaying,and the combinations of springs and weightscurtail vertical movements. The attenuatorstame seismic motions by a factor of 10–12, re-ports VIRGO spokesperson Adalbert Gia-zotto of the National Institute for NuclearPhysics in Italy, one of the research groupsparticipating in VIRGO. That attenuationenables the detector to reach its cutoff fre-quency of 10 hertz.

A second problem is thermal noise, espe-cially that caused by the laser beam itself: thelaser spots hit the center of the mirrors, heat-ing them unevenly and thereby deformingthem. In anticipation of future upgrades thatwould boost beam strength (and detectionsensitivity), VIRGO designers want to incor-porate cryogenic coolers, although excessive

cooling will add mechanical noise at low fre-quencies, says physicist Flavio Vetrano of theUniversity of Urbino, Italy’s spokesperson forVIRGO.

LIGO wants to introduce seismic isola-tion and thermal control (whereby the mir-rors are not cooled but heated on the periph-ery to compensate for the heating at their cen-ters). These improvements are planned forthe next-generation LIGO detectors, whichshould be implemented around 2006, ac-cording to Lee Samuel Finn, who directs theCenter for Gravitational Wave Physics atPennsylvania State University.

Finn expects that merging massive blackholes will be the first objects to have their grav-itational waves detected. But because sourcesof gravitational radiation are poor emitters oflight, astronomers may have missed still un-known classes of objects. “The first thing wemight see may be something unanticipated. Iam optimistic in that regard,” Finn remarks.

VIRGO joins a growing family of small-er gravitational-wave detectors sproutingaround the globe, such as GEO in Germanyand TAMA in Japan. A simultaneous detec-tion of an unexpected signal by the world’sinterferometers would be crucial to provingthe existence of gravitational waves. Al-though contacts among the observatoriesright now are largely informal, Vetrano looksforward to a time when they will function asa single machine.

Alexander Hellemans is a writer based in Naples, Italy.

Gravitational-wave signals will beburied deeply in noise, so

scientists will have to know whatto look for. They will compare their

interferometer signals with so-called templates, or gravitational-

wave patterns. These templatescome from models of binary black

holes or neutron stars spiralingtoward a collision course.

Therefore, detecting a signaldepends to a large extent on the

correctness of these models.Unfortunately, the parameters,

such as velocities, spins andmasses of the objects, vary widely,

remarks Flavio Vetrano, Italy’sspokesperson for VIRGO: “We are

facing a catch-22: for recognizing asignal we should have good

templates, but for having goodtemplates we need a true signal.”

PICKINGA PATTERN

VIRGO INTERFEROMETER is built on a layer ofsediment in the alluvial plain of the Arno River inCascina near Pisa, Italy. VIRGO’s designers chose thissite because of its low level of microseismicity.



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National Energy Policy: Reportof the National Energy PolicyDevelopment Group. May 2001.Available through the Office of thePresident of the United States(www.whitehouse.gov/energy).

Clean Energy Blueprint: ASmarter National Energy Policyfor Today and the Future.Steven Clemmer et al. Union ofConcerned Scientists with theAmerican Council for an Energy-Efficient Economy, and the TellusInstitute, October 2001(www.ucsusa.org).

Advanced Technology Paths toGlobal Climate Stability:Energy for a GreenhousePlanet. Martin I. Hoffert et al. inScience, Vol. 298, pages 981–987;November 1, 2002.

World Energy Outlook 2002.International Energy Agency,2002.

Annual Energy Outlook 2003with Projections to 2025.Energy Information Administration,January 2003 (www.eia.doe.gov).

FURTHERREADING

Summer now often means rolling black-outs and brownouts—on top of risingutility bills and higher prices at the

pumps. Unpredictable circumstances canlead to energy headaches—hot weather part-ly caused California’s infamous shortages of2001—but the main culprit is inadequate in-vestment and lack of an integrated powergrid to transmit electricity from one area toanother during emergencies.

The chart shows an increasing gap be-tween consumption and domestic production,one that historically has been filled by im-porting fuels, mostlyoil and natural gas.The growing depen-dence on importsputs the U.S. at risk,not only because 53percent of the world’sproven oil reservesare in the volatilePersian Gulf regionbut because pipelinesand international sealanes must be pro-tected. Additionally,the growing need forimports contributesto the economic vul-nerability of the U.S.by increasing the for-eign trade debt [seeBy the Numbers, Feb-ruary 2000]. And ofcourse, fossil-fuel consumption produces car-bon dioxide and other heat-trapping gases,thereby contributing to global warming.

An endless supply of clean energy—say,from nuclear fusion plants or orbiting solarpanels beaming down microwave energy—

may someday be possible. But such radicaltechnology will not be available soon. To ad-dress America’s needs in the next 25 to 50years, the Bush administration detailed a con-troversial plan in 2001, favored by industry,called the National Energy Policy. It calls for,among other measures, investing huge sumsin the oil, gas, electricity and coal infrastruc-

tures, opening the Arctic National WildlifeRefuge in Alaska to oil and gas development,expanding the use of nuclear (fission) pow-er, and developing a national power-grid sys-tem to prevent local and regional electricityshortages.

Among the more prominent counterplansis the Clean Energy Blueprint, issued by aconsortium that includes the Union of Con-cerned Scientists (UCS). This strategy calls forconsiderably less investment in fossil-fuel in-frastructure and greater investment in re-newable energy. Of all such sources—solar,

geothermal and bio-mass—wind poweremerges as the mostimportant to theUCS, which consid-ers it essential to anyplan to meet U.S. en-ergy needs over thenext two decades.The UCS estimatesthat in the 20th yearof implementation,the proposed mea-sures will reduce an-nual energy con-sumption by 20 per-cent as comparedwith the “businessas usual” forecast ofthe U.S. Energy In-formation Adminis-tration that under-

lies the administration proposal. This past June, U.S. Secretary of Energy

Spencer Abraham warned that the country iscritically low on natural gas. Whether thisnews will nudge the U.S. into making the re-ally big decisions about energy policy is un-clear. Few Americans feel that there is an en-ergy crisis, to judge by Gallup polls, whichconsistently show that “lack of energy” or“energy crisis” is at the bottom of their list ofimportant problems facing the nation.

Rodger Doyle can be reached [email protected]

Energy CrunchAVOIDING FUTURE SHORTAGES DEMANDS CRUCIAL CHOICES NOW BY RODGER DOYLE

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Buzz Off, HeatHornets may chill out with a bit of electricity,say a group of biologists and physicists fromTel Aviv University. Infrared images of hor-nets anesthetized in their nest revealed thatthe cuticle around body parts such as the ab-domen could be up to 3 degrees Celsius cool-er than the nest material. Evaporation fromthe mouth cannot account for the abdominalcooling; rather the researchers assert that thehornets’ cuticles may be thermoelectric. Suchmaterials change temperature when an elec-tric current passes through them. But insectphysiologist Allen Gibbs of the University ofArizona thinks that evaporative coolingcould in fact do the trick and that the mea-surements may be misleading because of dif-ferences in air and nest temperature. Until

studies of the cuticle’s thermal and electricalconductivity and the hornets’ water loss andmetabolic activity come in, he says, “put medown as a skeptic.” The paper scorches thepages of the May 30 Physical Review Letters.

—JR Minkel

V I S U A L R E C O G N I T I O N

If U Cn Rd Ths . . .Despite having read 100 million words or more by age25, the average literate person does not have an easi-er time identifying common words compared with anyword of the same length. Researchers asked volunteersto make out familiar English words or letters hiddenin various levels of contrast. Reading efficiency waslinked not to how common a word was but to howmany letters it had: four-letter words were twice ashard to recognize as two-letter ones, for instance. Fur-thermore, words proved unreadable unless tiny fea-tures of each letter are recognizable, demonstrating severe limitations on the brain’s ability toprocess visual patterns, the researchers say. Such handicaps may have arisen to suppress re-flexive attempts to recognize a deluge of inconsequential details. The findings appear in theJune 12 Nature. —Charles Choi

E N V I R O N M E N T

Not So Friendly HydrogenBurning oil and gas can lead to smog, acid rain and global warming, whereas burned hydrogengenerates only water. But hydrogen engines may not prove as environmentally friendly asthought. Current systems are leaky, with 10 percent or more of hydrogen escaping uncombusted.California Institute of Technology researchers calculate that if hydrogen fuel cells replaced alloil- and gas-burning technologies, people would release four to eight times more hydrogen intothe atmosphere than they do now. The hydrogen would oxidize and form water, clouding theoverlying stratosphere, and the resulting cooling would encourage ozone-destroying chemicalreactions. The investigators say that preventing hydrogen seepage could offset this damage, ascould decreases in ozone-eating chlorofluorocarbons over time and better-than-expected hy-drogen absorption by soil. Their report appears in the June 13 Science. —Charles Choi

ORIENTAL HORNETS (Vespa orientalis), shown heremunching raw meat, may stay cool with electricity.

FEATURES on letters help enable reading.

Fans of shoot-’em-up video gamesprocess visual information betterthan nongamers. C. Shawn Green

and Daphne Bavelier of theUniversity of Rochester tested

subjects on various tasks, such asrecognizing an object in a

sequence and counting severalitems at once. Practice with action

games enabled nonplayers toimprove their visual attention

skills—useful perhaps in drivingand in combat training.

Number of items flashed that gameplayers could see: 4.9

Number that nongame playerscould see: 3.3

Accuracy of game players: 78

Accuracy of nongame players: 65

Increase in flashed items seenamong those trained on action

game Medal of Honor: 1.7

Increase in those trained on puzzlegame Tetris: 0

Daily training time: 1 hour

Number of training days: 10

DATA POINTS:TRIGGER HAPPY


P H Y S I C S

Forced AttractionOpposites attract and like repels, at leastwhen it comes to electricity and magnetism.Now physicists suggest that it could be possi-ble to bind positive charges to other positivecharges. The result could be otherwise im-possible “molecules,” in which proton-loadedatomic nuclei stick together without electrons.The trick: high-power lasers, which could pushatomic nuclei and keep them spinning aroundone another instead of exploding apart. Suffi-

ciently intense laser pulses could then slam thenuclei together. Such experiments could boostunderstanding about nuclear activity in starsand improve laser-driven fusion reactor de-sign. The hope is that tabletop equipmentcould generate fast enough laser pulses for nu-clei confinement or collision. The team at theNational Research Council Canada in Ot-tawa presents its findings in the June 20 Phys-ical Review Letters. —Charles Choi


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■ A common gene therapy vector, a leukemia retrovirus, integratesits genes near active genes,possibly disrupting them.Researchers previously thoughtthat the integration occurredrandomly and thus did not pose ahazard to a patient’s genes. Thefinding may explain recent failedtrials in which patientsdeveloped leukemia.

Science, June 13, 2003

■ Keep the mystique: Rather thanwearing casual clothing such asjeans and sneakers, physiciansare better off donning white labcoats with name tags. Patientsfeel that such attire projectsconfidence and inspires trust.

Archives of Internal Medicine, June 9, 2003

■ A noise thermometer can go fromnear absolute zero to roomtemperature. Made of metalstrips around an insulator, it depends on the tunneling of electrons, which createstemperature-dependent “shot” noise.

Science, June 20, 2003

■ Saturn’s winds have died downfrom 1,700 kilometers per hourin the early 1980s to a currentspeed of 1,000 kph—a resultperhaps of the planet’s longseasonal cycles and equatorialshadows cast by its rings.

Nature, June 5, 2003

BRIEFPOINTS

E C O L O G Y

Fueling PredictionsWildfire predictions rely heavily on summerweather forecasts, alerting fire crews only a fewweeks in advance. But warnings might be extend-ed by a year or more, because long-term climatecan have an even greater influence than short-termweather. Anthony L. Westerling of the Scripps In-stitution of Oceanography and his colleagues cor-related more than 20 years of climate and vege-tation records with wildfire statistics. Their analy-sis reveals that the flammability of nonforestedregions—home to more than half of U.S. wild-fires—depends most on rainfall during previoussummers. If persistent drought kills off grasses and shrubs, then the next year’s fire season willbe less severe. In forests, the opposite is often true; although dry spells diminish kindling, theyalso make vegetation more combustible. The findings, in the May Bulletin of the AmericanMeteorological Society, could help douse blazing costs: U.S. agencies spent more than $1billion fighting the fires that ravaged some 6.4 million acres last year. —Sarah Simpson

B I O L O G Y

See under the SeaClear vision certainly helps get the job done.For the Moken people, who live along thecoasts of Myanmar and Thailand, that meansbeing able to spot clams, sea cucumbers andother food on the ocean bot-tom. But as any swimmerknows, blurriness rules under-water. Anna Gislén of LundUniversity in Sweden and hercolleagues have uncovered anunusual adaptation: unlikeEuropean kids, Moken chil-dren “accommodate,” or fo-cus on objects, when they are

underwater. Moreover, the Moken reducethe size of their pupils, a reflex resulting fromaccommodation and perhaps from a physio-logical response to diving. Like a pinholecamera, an eye with a smaller pupil producessharper images. The adaptations enable the

Moken to see twice as well un-derwater as landlubbers do.Gislén is testing Swedish chil-dren to determine if underwa-ter focusing can be learned.“Preliminary data suggest thisability is very much train-able,” she remarks. The May13 Current Biology containsthe report. —Philip Yam

CONSTRICTED PUPILS show thatthe Moken can focus underwater.

BETTER FORECASTS may prevent blazes such as this one last year in California’s Anza-BorregoDesert State Park.


When David G. Grier got a tenure-track teaching posi-tion at the University of Chicago in 1992, he expectedto continue the work on high-temperature supercon-ductors that he had completed as a postdoctoral fellowat Bell Labs. Biding his time while his superconductorlaboratory was being set up, he decided to carry outwhat he thought would be a quick and easy experimenton suspensions of particles, called colloids. These ma-terials serve as a means for scientists to study how theatoms in metal crystals or other collections of tiny par-ticles interact with one another, without having tomove around individual atoms.

“We whipped up the experiment, and nothing waswhat it was supposed to be,” Grier says. One-micron-diameter latex beads carrying a negative electrical chargehad demonstrated a strong attraction when they were

placed in a solution of water between two closely spacedparallel plates also bearing a negative charge. “It con-tradicted a 50-year-old theory that holds that likecharges in a solution repel,” he adds. The technologyneeded to understand the colloids was one that he hadlearned to use at Bell Labs, where it had been invented.

Optical tweezers employ forces applied by a highlyfocused laser beam to trap and move objects ranging insize from that of a protein (five nanometers) up to thatof a collection of dozens of cells (100 microns). Thetweezers trap the particles where the light is most intense.Grier and his students manipulated two tweezers to mea-sure the interaction between microscopic beads. Eachtweezer captured one bead and, when the trap wasturned off, released it. The group then observed with adigital-video microscope how quickly the two beadsmoved toward or away from each other, enabling a cal-culation of the forces exerted by one bead on another.But the researchers needed to do more. They wanted tosee whether this attractive force exists among complexconfigurations of particles. This finding might afford abetter comprehension of biological systems—how DNAand proteins, for instance, pack tightly together in thecell nucleus. But aligning multiple optical tweezers tomeasure forces among even four particles was difficult.

One student, Eric R. Dufresne, was looking througha surplus catalogue and came across a $5 device thatseparates the beam from a laser pointer into a four-by-four array that fans out from the original beam. “It wasworth trying for five bucks, but we thought we should-n’t be disappointed if it didn’t pan out,” Grier recalls.The experiment proceeded without a hitch. “We wroteit up and patented it,” he says.

The patent covers the use of a computer-designeddiffraction grating, a type of hologram that takes a sin-gle beam and breaks it up into an array of beams, eachone of which forms an optical trap for particles of mi-cron or nanometer dimensions. The invention tran-scends the run-of-the-mill optical tweezers. Regular


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Hands of LightMoving particles with photons leads to a new form of nanomanufacturing By GARY STIX

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OPTICAL VORTICES generated by a laser beam drive microscopic beads in circles.


light pincers are often compared to chopsticks or pairedfingers. Holographic optical tweezers, as they are called,are more akin to a hand, with its ability to move fingersindependently at various angles.

The $5 solution paved the way to the next, more chal-lenging problem. The diffraction gratings purchased fromthe catalogue were limited to 16 beams and did not al-low the beams to be manipulated independently. ButGrier and his team already foresaw the possibility ofmaneuvering hundreds or even thousands of particlesin a three-dimensional space. They tried a variety of ap-proaches—ranging from chip-making lithography toolsto liquid-crystal displays such as those used in a SonyWatchman—that would allow them to create and controldiffracted beams separately. “This was a slow and diffi-cult process to get something working,” Grier remembers.

The answer came in the form of liquid-crystal spa-tial light modulators used in pattern matching for fin-gerprint identification and retinal scanning. By chang-ing the orientation of the molecules that make up theliquid crystals, the modulators reshape the wavefrontof the incoming light beam to display the image encod-ed in a computer-designed hologram. The pattern onthe hologram can project hundreds or thousands ofbeams that can be moved forward, back, sideways, upor down or can twist the light in a corkscrew trajecto-ry that creates a vortex.

The tweezer array showed successfully that thesame attraction that occurs between a pair of similarlycharged particles is also present in large clusters ofthem. And the researchers realized that the technologymight be good for other things. “People were asking,‘What are the applications?’” Grier says. “At that pointwe didn’t have any. We had a lot of ideas, but very fewof them had been demonstrated.” The university tech-nology office shopped the idea around. Lewis Gruber,a co-founder of a biotechnology company called Hyseq(now Nuvelo), had retired to Chicago and was con-tacted by the university. When Grier and his studentsdemonstrated the tweezer array, Gruber was impressed:“It’s bigger than genomics. It was the most excitingthing I had ever seen.” Gruber perceived that the tweez-er array was not just a tool for biology but could beused in manufacturing materials for markets from pho-tonics to food processing.

In late fall of 2000, a few months after witnessingGrier’s demonstration, Gruber had licensed the patentsheld by the University of Chicago to start a new com-pany. The first few employees, along with the membersof Grier’s lab, were asked to come up with a name. Grier’s suggestion of the Very Nice Optical Tweezer

Company was immediately vetoed. Then he remem-bered that high-tech companies were supposed to havenames studded with letters like “X” or “Q.” Thus wasborn Arryx. The company set up quarters on two base-ment floors in downtown Chicago, just down the streetfrom the signature Wrigley building.

Arryx developed a point-and-click system that al-lows a particle to be imaged, highlighted, trapped andmoved along a trajectory outlined on the screen. Withthe telecommunications boom at its peak, the compa-ny began to research using holographic optical tweez-ers to make photonic crystals that could switch or am-

plify optical signals. Tweezer arrays with dozens ofbeams could manipulate particles to create defects in anordered colloidal crystal. Thus altered, the crystalscould form components for optical networks, such as adevice that channels light signals around corners withvery low loss in energy.

After the telecom market imploded, the technolo-gy demonstrated the versatility that Gruber had origi-nally perceived. The evaporation in demand for next-generation optical networks caused Arryx to turn itssights toward biology. Its first product, the BioRyx 200,is a $275,000 research tool sold to the likes of EmoryUniversity and the National Institute of Standards andTechnology. The company’s first application-specificproducts will try to best the efficiency of conventionalflow cytometry techniques, sorting hundreds or thou-sands of cells at once. Further elaboration of the tech-nology may enable sorting of cells or proteins morequickly and precisely than an approach known as gelelectrophoresis. The work on photonic crystals was notfor naught, though. These devices may soon be incor-porated into the manufacture of optical sensors for de-tection of bioweapons or toxic chemicals.

Optical tweezers are more than a hand of light.They are more like a hand that has power screwdriversor cutting tools attached to the tips of each finger. Eachbeam can apply torque to an object or make incisionsin a material. In the future, holographic tweezers mayassemble nanocomputers from carbon nanotubes, pu-rify drugs, perform noninvasive surgery or create spin-ning liquid vortices that act as microscopic pumps. Thisdiversity may allow holographic optical tweezers to be-come a critical tool in the still emerging disciplines ofnanotechnology and microelectromechanics.


Optical tweezer arrays are not just for biology but could be used in markets

from photonics to food processing.


A patent gives the holder the right to exclude othersfrom making, using or selling an invention for 20 yearsfrom the filing date. The holders of the following selec-tion of patents—a continuation of last month’s columnon out-of-the-ordinary issuances from the U.S. Patent

and Trademark Office—willprobably not have to worrytoo much about having tomount an aggressive programto protect their intellectualproperty.

Method of treating chestpain, patent 6,457,474, CarlE. Hanson of St. Paul, Minn.This inventor has patentedlime juice to replace nitroglyc-erin as a treatment for chestpain such as angina pectoris.Making the patented inven-

tion requires only modest skill. “Limeade in non-con-centrated form,” according to the document, “was pre-pared by opening a can of the Minute Maid brand Pre-mium All Natural Frozen Concentrate for Limeade,removing the contents and placing it in a pitcher, addingapproximately 52 fluid ounces (about 4.5 cans) of tapwater to the frozen concentrate and stirring.

“The pitcher was placed in the refrigerator so thatthe contents would cool. I drank approximately 2 to 3glasses of limeade daily and did not notice the reoccur-rence of chest pain.” The lime juice can also be admin-istered intravenously or by the angina sufferer’s placingthe frozen concentrate directly into his or her mouth.“The present invention is advantageous in that a patientcan easily determine if the medicine is properly ingest-ed. Lime juice has a very noticeable taste that disappearsafter it leaves the mouth. Since the juice is regularlystored in the refrigerator or freezer, it can be quickly lo-cated by the patient, particularly at nighttime where therefrigerator light plays a helpful role.”

Process for phase-locking human ovulation/menstrual cycles, patent 6,497,718, assigned to thesecretary of the U.S. Air Force. “By simulating moon-light with nocturnal light exposures [with a 100-wattlightbulb], the menstrual cycles of women could bebrought nearer to the lunar cycle of 29.5 days. . . . Theidea behind it is that, during evolution, the fertility cy-cle of humans and other primates was phase-locked tothe moon and that [the] full moon coincided with ovu-lation.. . . It would also explain, on a rational basis, thecause of the well-known ‘romantic’ effect of the fullmoon.” The technique, notes the patent, would allowthe rhythm method to be more reliably adopted.

Talking moving dieter’s plate, patent 6,541,713, Albertine White of Los Angeles. “This invention pro-vides a plate and scale combination with a pre-pro-grammed repertoire of statements which can be madeby the device depending on the stimulus. The apparatuscan be programmed to encourage dieters not to placeexcessive meal portions on the plate or, alternatively, itcan be programmed to encourage persons battlinganorexia to have normal sized meals rather than mealswhich are too small. . . . The invention might roll awayfrom the dieter, or a lid might close, denying access tothe food. The invention might tremble in ‘anxiety’ overthe amount of food being measured or the inventionmight even be able to flush the food into itself if toogreat a portion is measured.”

Apparatus and method for detecting and identify-ing organisms, especially pathogens, using the aurasignature of the organism, patent 6,466,688, ThomasP. Ramstack of Silver Spring, Md. A technology for de-tecting “auras,” or “electromagnetic fields created by theaction of the cells of all living organisms.” It purported-ly screens for pathogens involved in disease or biowar-fare. “Typically, the auras of diseased persons bear tell-tale colors, and the auras may have holes or gaps not nor-mally present in healthy persons. An illness can often bedetected as a dark brown glow in a person’s aura.”


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What a Little Limeade Can DoOwning the rights for frozen juice to treat angina and for lunar birth control By GARY STIX



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In 1670 English poet John Dryden penned this expression of hu-mans in a state of nature: “I am as free as Nature first mademan .. . /When wild in woods the noble savage ran.” A centurylater, in 1755, French philosopher Jean-Jacques Rousseau can-onized the noble savage in Western culture by proclaiming that“nothing can be more gentle than he in his primitive state, whenplaced by nature at an equal distance from the stupidity of brutesand the pernicious good sense of civilized man.”

From the Disneyfication of Pocahontas to Kevin Costner’seco-pacifist Native Americans in Dances with Wolves and from

postmodern accusations of cor-ruptive modernity to modern an-thropological theories that indige-nous people’s wars are just ritual-ized games, the noble savageremains one of the last epic cre-ation myths of our time.

Science reveals a rather differ-ent picture of humanity in its nat-ural state. In a 1996 study Uni-

versity of Michigan ecologist Bobbi S. Low analyzed 186 pre-industrial societies and discovered that their relatively low en-vironmental impact is the result of low population density, in-efficient technology and lack of profitable markets, not con-scious efforts at conservation. Anthropologist Shepard KrechIII, in his 1999 book The Ecological Indian, shows that in anumber of Native American communities, large-scale irrigationpractices led to the collapse of their societies.

Even the reverence for big game animals that we have beentold was held by Native Americans is a fallacy—many believedthat common game animals such as elk, deer, caribou, beaverand especially buffalo would be physically reincarnated, thuseasily replaced, by the gods. Given the opportunity to hunt biggame animals to extinction, they did. The evidence is now over-whelming that many large mammals went extinct at the sametime that the first Americans began to populate the continent.

Ignoble savages were nasty to one another as well as to theirenvironments. Surveying primitive and civilized societies, Uni-versity of Illinois anthropologist Lawrence H. Keeley, in his 1996

book War before Civilization, demonstrates that prehistoric warwas, relative to population densities and fighting technologies, atleast as frequent (measured in years at war versus years at peace),as deadly (determined by percentage of deaths resulting fromconflict) and as ruthless (judged by the killing and maiming ofnoncombatants, women and children) as modern war. One pre-Columbian mass grave in South Dakota, for example, yielded theremains of 500 scalped and mutilated men, women and children.

In Constant Battles, a recent and exceptionally insightfulstudy of this concept, Harvard University archaeologist StevenA. LeBlanc quips, “Anthropologists have searched for peacefulsocieties much like Diogenes looked for an honest man.” Con-sider the evidence from a 10,000-year-old Paleolithic site alongthe Nile River: “The graveyard held the remains of 59 people,at least 24 of whom showed direct evidence of violent death, in-cluding stone points from arrows or spears within the body cav-ity, and many contained several points. There were six multi-ple burials, and almost all those individuals had points in them,indicating that the people in each mass grave were killed in a sin-gle event and then buried together.”

LeBlanc’s survey reveals that even cannibalism, long thoughtto be a form of primitive urban legend (noble savages wouldnever eat one another, would they?), is supported by powerfulphysical artifacts: broken and burned bones, cut marks onbones, bones cracked open lengthwise to get at the marrow, andbones inside cooking jars hacked so that they would fit. Such ev-idence for prehistoric cannibalism has been uncovered in Mex-ico, Fiji and parts of Europe. The definitive (and gruesome)proof came with the discovery of the human muscle proteinmyoglobin in the fossilized human feces of a prehistoric Anasazipueblo Indian. Savage, yes. Noble, no.

Roman statesman Cicero noted, “Although physicians fre-quently know their patients will die of a given disease, they nev-er tell them so. To warn of an evil is justified only if, along withthe warning, there is a way of escape.” As we shall see in parttwo of this column, there is an escape from our disease.

Michael Shermer is publisher of Skeptic (www.skeptic.com)and author of Why People Believe Weird Things.

The Ignoble SavageScience reveals humanity’s heart of darkness By MICHAEL SHERMER

“Anthropologistshave searched

for peacefulsocieties much

like Diogeneslooked for

an honest man.”



CENSORS of the

Biologists have been surprised

to discover that most animal

and plant cells contain a built-in system

to silence individual genes by shredding the

RNA they produce. Biotech companies are already working

to exploit it


the transcription machinery of the cell would expressevery gene in the genome at once: unwinding the DNAdouble helix, transcribing each gene into single-strand-ed messenger RNA and, finally, translating the RNAmessages into their protein forms.

No cell could function amid the resulting cacoph-ony. So cells muzzle most genes, allowing an appro-priate subset to be heard. In most cases, a gene’s DNAcode is transcribed into messenger RNA only if a par-ticular protein assemblage has docked onto a specialregulatory region in the gene.

Some genes, however, are so subversive that theyshould never be given freedom of expression. If thegenes from mobile genetic elements were to success-fully broadcast their RNA messages, they could jumpfrom spot to spot on the DNA, causing cancer or oth-er diseases. Similarly, viruses, if allowed to expresstheir messages unchecked, will hijack the cell’s proteinproduction facilities to crank out viral proteins.

Cells have ways of fighting back. For example, bi-ologists long ago identified a system, the interferon re-sponse, that human cells deploy when viral genes entera cell. This response can shut off almost all gene ex-pression, analogous to stopping the presses. And just

within the past several years, scientists have discovereda more precise and—for the purposes of research andmedicine—more powerful security apparatus built intonearly all plant and animal cells. Called RNA interfer-ence, or RNAi, this system acts like a censor. When athreatening gene is expressed, the RNAi machinery si-lences it by intercepting and destroying only the of-fender’s messenger RNA, without disturbing the mes-sages of other genes.

As biologists probe the modus operandi of this cel-lular censor and the stimuli that spur it into action, theirfascination and excitement are growing. In principle,scientists might be able to invent ways to direct RNAinterference to stifle genes involved in cancer, viral in-fection or other diseases. If so, the technology couldform the basis for a new class of medicines.

Meanwhile researchers working with plants,worms, flies and other experimental organisms have al-ready learned how to co-opt RNAi to suppress nearlyany gene they want to study, allowing them to begin todeduce the gene’s purpose. As a research tool, RNAihas been an immediate success, allowing hundreds oflaboratories to tackle questions that were far beyondtheir reach just a few years ago.


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bserved on a microscope slide, a living cell appears serene. But underneath its tranquil facade, it buzzeswith biochemical chatter. The DNA genome inside every cell of a plant or animal contains many thousands of genes. Left to its own devices,

O


Whereas most research groups are using RNA interferenceas a means to an end, some are investigating exactly how thephenomenon works. Other labs (including our own) are un-covering roles for the RNAi machinery in the normal growth anddevelopment of plants, fungi and animals—humans among them.

A Strange SilenceTHE FIRST HINTS of the RNAi phenomenon surfaced 13 yearsago. Richard A. Jorgensen, now at the University of Arizona,and, independently, Joseph Mol of the Free University of Am-sterdam inserted into purple-flowered petunias additional copiesof their native pigment gene. They were expecting the engineeredplants to grow flowers that were even more vibrantly violet. Butinstead they obtained blooms having patches of white.

Jorgensen and Mol concluded that the extra copies weresomehow triggering censorship of the purple pigment genes—

including those natural to the petunias—resulting in variegatedor even albino-like flowers. This dual censorship of an insertedgene and its native counterpart, called co-suppression, was lat-er seen in fungi, fruit flies and other organisms.

Clues to the mystery of how genes were being silenced camea few years later from William G. Dougherty’s lab at OregonState University. Dougherty and his colleagues started with to-bacco plants that had been engineered to contain within their

DNA several copies of the CP (coat protein) gene from tobaccoetch virus. When these plants were exposed to the virus, someof the plants proved immune to infection. Dougherty proposedthat this immunity arose through co-suppression. The plants ap-parently reacted to the initial expression of their foreign CPgenes by shutting down this expression and subsequently alsoblocking expression of the CP gene of the invading virus (whichneeded the coat protein to produce an infection). Dougherty’slab went on to show that the immunity did not require synthe-sis of the coat protein by the plants; something about the RNAtranscribed from the CP gene accounted for the plants’ resistanceto infection.

The group also showed that not only could plants shut offspecific genes in viruses, viruses could trigger the silencing of se-lected genes. Some of Dougherty’s plants did not suppress theirCP genes on their own and became infected by the virus, whichreplicated happily in the plant cells. When the researchers latermeasured the RNA being produced from the CP genes of the af-fected plants, they saw that these messages had nearly van-ished—infection had led to the CP genes’ inactivation.

Meanwhile biologists experimenting with the nematodeCaenorhabditis elegans, a tiny, transparent worm, were puzzlingover their attempts to use “antisense” RNA to inactivate thegenes they were studying. Antisense RNA is designed to pair upwith a particular messenger RNA sequence in the same way thattwo complementary strands of DNA mesh to form a double he-lix. Each strand in DNA or RNA is a chain of nucleotides, ge-netic building blocks represented by the letters A, C, G and ei-ther U (in RNA) or T (in DNA). C nucleotides link up with Gs,and As pair with Us or Ts. A strand of antisense RNA binds toa complementary messenger RNA strand to form a double-stranded structure that cannot be translated into a useful protein.

Over the years, antisense experiments in various organismshave had only spotty success. In worms, injecting antisense RNAsseemed to work. To everyone’s bewilderment, however, “sense”RNA also blocked gene expression. Sense RNA has the same se-quence as the target messenger RNA and is therefore unable tolock up the messenger RNA within a double helix.

The stage was now set for the eureka experiment, performedfive years ago in the labs of Andrew Z. Fire of the Carnegie In-stitution of Washington and Craig C. Mello of the University ofMassachusetts Medical School. Fire and Mello guessed that theprevious preparations of antisense and sense RNAs that werebeing injected into worms were not totally pure. Both mixturesprobably contained trace amounts of double-stranded RNA. They


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■ Scientists have long had the ability to introduce alteredgenes into experimental organisms. But only within thepast few years have they discovered a convenient andeffective way to turn off a specific gene inside a cell.

■ It turns out that nearly all plant and animal cells haveinternal machinery that uses unusual forms of RNA, thegenetic messenger molecule, to naturally silenceparticular genes.

■ This machinery has evolved both to protect cells fromhostile genes and to regulate the activity of normal genesduring growth and development. Medicines might also bedeveloped to exploit the RNA interference machinery toprevent or treat diseases.

Overview/RNA Interference

PURPLE PETUNIAS offered the first clues to the existence of gene censorsin plants. When extra pigment genes were inserted into normal plants (left), the flowers that emerged ended up with areas that strangely lacked color (center and right).


suspected that the double-stranded RNA was alerting the censors.To test their idea, Fire, Mello and their colleagues inoculat-

ed nematodes with either single- or double-stranded RNAs thatcorresponded to the gene unc-22, which is important for musclefunction. Relatively large amounts of single-stranded unc-22RNA, whether sense or antisense, had little effect on the nema-todes. But surprisingly few molecules of double-stranded unc-22RNA caused the worms—and even the worms’ offspring—totwitch uncontrollably, an unmistakable sign that something hadstarted interfering with unc-22 gene expression. Fire and Melloobserved the same amazingly potent silencing effect on nearlyevery gene they targeted, from muscle genes to fertility and via-bility genes. They dubbed the phenomenon “RNA interference”to convey the key role of double-stranded RNA in initiating cen-sorship of the corresponding gene.

Investigators studying plants and fungi were also closingin on double-stranded RNA as the trigger for silencing. Theyshowed that RNA strands that could fold back on themselvesto form long stretches of double-stranded RNA were potent in-ducers of silencing. And other analyses revealed that a gene thatenables cells to convert single-stranded RNA into double-stranded RNA was needed for co-suppression. These findingssuggested that Jorgensen and Mol’s petunias recognized the ex-tra pigment genes as unusual (through a mechanism that is still

mysterious) and converted their messenger RNAs into double-stranded RNA, which then triggered the silencing of both theextra and native genes. The concept of a double-stranded RNAtrigger also explains why viral infection muzzled the CP genesin Dougherty’s plants. The tobacco etch virus had created dou-ble-stranded RNA of its entire viral genome as it reproduced,as happens with many viruses. The plant cells responded by cut-ting off the RNA messages of all genes associated with the virus,including the CP genes incorporated into the plant DNA.

Biologists were stunned that such a powerful and ubiquitoussystem for regulating gene expression had escaped their noticefor so long. Now that the shroud had been lifted on the phe-nomenon, scientists were anxious to analyze its mechanism ofaction and put it to gainful employment.

Slicing and Dicing Genetic MessagesRNA INTERFERENCE was soon observed in algae, flatwormsand fruit flies—diverse branches of the evolutionary tree.Demonstrating RNAi within typical cells of humans and othermammals was considerably trickier, however.

When a human cell is infected by viruses that make long dou-ble-stranded RNAs, it can slam into lockdown mode: an enzymeknown as PKR blocks translation of all messenger RNAs—both

normal and viral—and the enzyme RNAse L indiscriminatelydestroys the messenger RNAs. These responses to double-stranded RNA are considered components of the so-called in-terferon response because they are triggered more readily afterthe cells have been exposed to interferons, molecules that in-fected cells secrete to signal danger to neighboring cells.

Unfortunately, when researchers put artificial double-strand-ed RNAs (like those used to induce RNA interference in wormsand flies) into the cells of mature mammals, the interferon re-sponse indiscriminately shuts down every gene in the cell. Adeeper understanding of how RNA interference works wasneeded before it could be used routinely without setting off theinterferon alarms. In addition to the pioneering researchers al-

ready mentioned, Thomas Tuschl of the Rockefeller University,Phillip D. Zamore of the University of Massachusetts MedicalSchool, Gregory Hannon of Cold Spring Harbor Laboratoryin New York State and many others have added to our currentunderstanding of the RNA interference mechanism.

RNAi appears to work like this: Inside a cell, double-stranded RNA encounters an enzyme dubbed Dicer. Using thechemical process of hydrolysis, Dicer cleaves the long RNA intopieces, known as short (or small) interfering RNAs, or siRNAs.Each siRNA is about 22 nucleotides long.

Dicer cuts through both strands of the long double-strand-ed RNA at slightly staggered positions so that each resultingsiRNA has two overhanging nucleotides on one strand at either


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NELSON C. LAU and DAVID P. BARTEL have been studying microRNAsand other small RNAs that regulate the expression of genes. Lau iscompleting a doctoral degree at the Whitehead Institute and theMassachusetts Institute of Technology. Bartel started his researchgroup at the Whitehead Institute in 1994, after earning a Ph.D. atHarvard University. Bartel is also an associate professor at M.I.T.and a co-founder of Alnylam Pharmaceuticals, which is developingRNAi-based therapeutics. Lau and Bartel are among the recipientsof the 2002 AAAS Newcomb Cleveland Prize.

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Surprisingly FEW MOLECULES of double-stranded RNA made the worms—and even theiroffspring—TWITCH UNCONTROLLABLY.

GLOWING NEMATODES proved that RNA interference operates in animals as well as plants. When worms whose cells express a gene for a fluorescentprotein (left) were treated with double-stranded RNA corresponding to thegene, the glow was extinguished ( right).


end [see box above]. The siRNA duplex is then unwound, andone strand of the duplex is loaded into an assembly of proteinsto form the RNA-induced silencing complex (RISC).

Within the silencing complex, the siRNA molecule is posi-tioned so that messenger RNAs can bump into it. The RISC willencounter thousands of different messenger RNAs that are ina typical cell at any given moment. But the siRNA of the RISCwill adhere well only to a messenger RNA that closely com-plements its own nucleotide sequence. So, unlike the interferonresponse, the silencing complex is highly selective in choosingits target messenger RNAs.

When a matched messenger RNA finally docks onto thesiRNA, an enzyme known as Slicer cuts the captured messen-ger RNA strand in two. The RISC then releases the two mes-senger RNA pieces (now rendered incapable of directing pro-tein synthesis) and moves on. The RISC itself stays intact, freeto find and cleave another messenger RNA. In this way, theRNAi censor uses bits of the double-stranded RNA as a black-

list to identify and mute corresponding messenger RNAs.David C. Baulcombe and his co-workers at the Sainsbury

Laboratory in Norwich, England, were the first to spot siRNAs,in plants. Tuschl’s group later isolated them from fruit fly em-bryos and demonstrated their role in gene silencing by synthe-sizing artificial siRNAs and using them to direct the destructionof messenger RNA targets. When that succeeded, Tuschl won-dered whether these short snippets of RNA might slip under theradar of mammalian cells without setting off the interferon re-sponse, which generally ignores double-stranded RNAs that areshorter than 30 nucleotide pairs. He and his co-workers put syn-thetic siRNAs into cultured mammalian cells, and the experi-ment went just as they expected. The target genes were silenced;the interferon response never occurred.

Tuschl’s findings rocked the biomedical community. Ge-neticists had long been able to introduce a new gene into mam-malian cells by, for example, using viruses to ferry the gene intocells. But it would take labs months of labor to knock out a gene


GENETIC CENSORSHIP: HOW IT WORKS

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NORMAL GENE EXPRESSION TRIGGERS OF RNA SILENCING

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HOW RNAi SUPPRESSESGENE EXPRESSION

GLOWING CELLS revealsuccessful translationof a gene (encodingthe lamin protein) intoprotein form.

Cell unwinds RNA strands

siRNA ormicroRNA


of interest to ascertain the gene’s function. Now the dream ofeasily silencing a single, selected gene in mammalian cells wassuddenly attainable. With siRNAs, almost any gene of interestcan be turned off in mammalian cell cultures—including humancell lines—within a matter of hours. And the effect persists fordays, long enough to complete an experiment.

A Dream ToolAS HELPFUL AS RNA interference has become to mammal bi-ologists, it is even more useful at the moment to those who studylower organisms. A particular bonus for those studying wormsand plants is that in these organisms the censorship effect is am-plified and spread far from the site where the double-strandedRNA was introduced. This systemic phenomenon has allowedbiologists to exploit RNAi in worms simply by feeding them bac-teria engineered to make double-stranded RNA correspondingto the gene that should be shut down.

Because RNA interference is so easy to induce and yet so

powerful, scientists are thinking big. Now that complete ge-nomes—all the genes in the DNA—have been sequenced for avariety of organisms, scientists can use RNA interference to ex-plore systematically what each gene does by turning it off. Re-cently four groups did just that in thousands of parallel exper-iments, each disabling a different gene of C. elegans. A similargenome-wide study is under way in plants, and several consor-tia are planning large RNAi studies of mammalian cells.

RNA interference is being used by pharmaceutical compa-nies as well. Some drug designers are exploiting the effect as ashortcut to screen all genes of a certain kind in search of promis-ing targets for new medicines. For instance, the systematic si-lencing of genes using RNAi could allow scientists to find a genethat is critical for the growth of certain cancer cells but not soimportant for the growth of normal cells. They could then de-velop a drug candidate that interferes with the protein productof this gene and then test the compound against cancer. Biotechfirms have also been founded on the bet that gene silencing by


A CELL CAN CENSOR the expression of an individual gene inside it byinterfering with the messenger RNA (mRNA) transcribed from theoffending gene, thus preventing the RNA from being decoded byribosomes into active protein, as normally happens (left panel). Thecensorship machinery is triggered by small, double-stranded RNAmolecules with ragged ends. An enzyme called Dicer chemically snipssuch short interfering RNAs (siRNAs) from longer double-stranded RNAsproduced by self-copying genetic sequences (a) or viruses (b).Regulatory RNA sequences known as microRNA precursors (c) are alsocleaved by Dicer into this short form. And scientists can use lipidmolecules to insert artificial siRNAs into cells (d).

The RNA fragments separate into individual strands (bottom panel),which combine with proteins to form an RNA-induced silencing complex(RISC). The RISC then captures mRNA that complements the short RNAsequence. If the match is essentially perfect, the captive message issliced into useless fragments (top row); less perfect matches elicit adifferent response. For instance, they may cause the RISC to blockribosome movements and thus halt translation of the message intoprotein form (bottom row).

b Double-stranded RNA from a replicating virus

d Artificial siRNAs delivered by lipidmolecules

GLOW FADED in cells that took up artificial siRNAs corresponding to the lamin gene.

RNA-induced silencingcomplex (RISC)

Cleaved mRNA

Mismatched RNA

If the two RNA strands are highly complementary, the mRNAis cleaved

If the two strands are somewhatmismatched, the RISC sticks to mRNA

Ribosomes stallon the mRNA

NO PROTEIN IS MADE


RNAi could itself become a viable therapy to treat cancer, viralinfections, certain dominant genetic disorders and other dis-eases that could be controlled by preventing selected genes fromgiving rise to illness-causing proteins.

Numerous reports have hinted at the promise of siRNAs fortherapy. At least six labs have temporarily stopped viruses—

HIV, polio and hepatitis C among them—from proliferating inhuman cell cultures. In each case, the scientists exposed the cellsto siRNAs that prompted cells to shut down production of pro-teins crucial to the pathogens’ reproduction. More recently,groups led by Judy Lieberman of Harvard Medical School andMark A. Kay of the Stanford University School of Medicinehave reported that siRNAs injected under extremely high pres-sure into mice slowed hepatitis and rescued many of the animalsfrom liver disease that otherwise would have killed them.

Despite these laboratory successes, it will be years before

RNAi-based therapies can be used in hospitals. The most diffi-cult challenge will probably be delivery. Although the RNAi ef-fect can spread throughout a plant or worm, such spreadingdoes not seem to occur in humans and other mammals. Also,siRNAs are very large compared with typical drugs and cannotbe taken as pills, because the digestive tract will destroy themrather then absorb them. Researchers are testing various waysto disseminate siRNAs to many organs and to guide themthrough cells’ outer membranes. But it is not yet clear whetherany of the current strategies will work.

Another approach for solving the delivery problem is gene

therapy. A novel gene that produces a particular siRNA mightbe loaded into a benign virus that will then bring the gene intothe cells it infects. Beverly Davidson’s group at the Universityof Iowa, for example, has used a modified adenovirus to deliv-er genes that produce siRNAs to the brain and liver of mice.Gene therapy in humans faces technical and regulatory diffi-culties, however.

Regardless of concerns about delivery, RNAi approacheshave generated an excitement not currently seen for antisenseand catalytic RNA techniques—other methods that, in princi-ple, could treat disease by impeding harmful messenger RNAs.This excitement stems in part from the realization that RNA in-terference harnesses natural gene-censoring machinery thatevolution has perfected over time.

Why Cells Have CensorsINDEED, THE GENE-CENSORING mechanism is thought tohave emerged about a billion years ago to protect some com-mon ancestor to plants, animals and fungi against viruses andmobile genetic elements. Supporting this idea, the groups ofRonald H. A. Plasterk at the Netherlands Cancer Institute andof Hervé Vaucheret at the French National Institute of Agri-cultural Research have shown that modern worms rely on RNAinterference for protection against mobile genetic elements andthat plants need it as a defense against viruses.

Yet RNA interference seems to play other biological roles aswell. Mutant worms and weeds having an impaired Dicer en-zyme or too little of it suffer from numerous developmental de-fects and cannot reproduce. Why should a Dicer deficiency causeanimals and plants to look misshapen?

One hypothesis is that once nature developed such an effec-tive mechanism for silencing the subversive genes in viruses andmobile DNA sequences, it started borrowing tools from theRNAi tool chest and using them for different purposes. Each cellhas the same set of genes—what makes them different from oneanother is which genes are expressed and which ones are not.

Most plants and animals start as a single embryonic cell that di-vides and eventually gives rise to a multitude of cells of varioustypes. For this to occur, many of the genes expressed in the em-bryonic cells need to be turned off as the organ matures. Othergenes that are off need to be turned on. When the RNAi ma-chinery is not defending against attack, it apparently pitches into help silence normal cellular genes during developmental tran-sitions needed to form disparate cell types, such as neurons andmuscle cells, or different organs, such as the brain and heart.

What then motivates the RNAi machinery to hush particu-lar normal genes within the cell? In some cases, a cell may nat-


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RNAi has temporarily STOPPED VIRUSES—HIV, polio and hepatitis C among them—fromproliferating IN HUMAN CELLS.

MICE LIGHT UP when injected with DNA containing the luciferase gene (left).But scientists took the shine off the mice by also injecting siRNAs that matchthe gene (right), thus demonstrating one way to exploit RNAi in mammals.


urally produce long double-stranded RNA specifically for thispurpose. But frequently the triggers are “microRNAs”—smallRNA fragments that resemble siRNAs but differ in origin. Where-as siRNAs come from the same types of genes or genomic regionsthat ultimately become silenced, microRNAs come from geneswhose sole mission is to produce these tiny regulatory RNAs.

The RNA molecule initially transcribed from a microRNAgene—the microRNA precursor—folds back on itself, forminga structure that resembles an old-fashioned hairpin. With thehelp of Dicer, the middle section is chopped out of the hairpin,and the resulting piece typically behaves very much like an siRNA—with the important exception that it does not censora gene with any resemblance to the one that produced it but in-stead censors some other gene altogether.

As with the RNAi phenomenon in general, it has taken biol-ogists time to appreciate the potential of microRNAs for regu-lating gene expression. Until recently, scientists knew of only twomicroRNAs, called lin-4 RNA and let-7 RNA, discovered by thegroups of Victor Ambros of Dartmouth Medical School andGary Ruvkun of Harvard Medical School. In the past two yearswe, Tuschl, Ambros and others have discovered hundreds of ad-ditional microRNA genes in worms, flies, plants and humans.

With Christopher Burge at M.I.T., we have estimated thathumans have between 200 and 255 microRNA genes—nearly1 percent of the total number of human genes. The microRNAgenes had escaped detection because the computer programs de-signed to sift through the reams of genomic sequence data hadnot been trained to find this unusual type of gene, whose finalproduct is an RNA rather than a protein.

Some microRNAs, particularly those in plants, guide the slic-ing of their mRNA targets, as was shown by James C. Carring-ton of Oregon State University and Zamore. We and BonnieBartel of Rice University have noted that plant microRNAs takeaim primarily at genes important for development. By clearingtheir messages from certain cells during development, RNAicould help the cells mature into the correct type and form theproper structures.

Interestingly, the lin-4 and let-7 RNAs, first discovered inworms because of their crucial role in pacing development, canemploy a second tactic as well. The messenger RNAs targetedby these microRNAs are only approximately complementary tothe microRNAs, and these messages are not cleaved. Some oth-er mechanism blocks translation of the messenger RNAs intoproductive proteins.

Faced with these different silencing mechanisms, biologistsare keeping open minds about the roles of small RNAs and theRNAi machinery. Mounting evidence indicates that siRNAs notonly capture messenger RNAs for destruction but can also directthe silencing of DNA—in the most extreme case, by literally edit-ing genes right out of the genome. In most cases, however, thesilenced DNA is not destroyed; instead it is more tightly packedso that it cannot be transcribed.

From its humble beginnings in white flowers and deformedworms, our understanding of RNA interference has come a longway. Almost all facets of biology, biomedicine and bioengi-neering are being touched by RNAi, as the gene-silencing tech-nique spreads to more labs and experimental organisms.

Still, RNAi poses many fascinating questions. What is thespan of biological processes that RNA interference, siRNAs andmicroRNAs influence? How does the RNAi molecular machin-ery operate at the level of atoms and chemical bonds? Do anydiseases result from defects in the RNAi process and in micro-RNAs? As these questions yield to science, our understandingof the phenomenon will gradually solidify—perhaps into afoundation for an entirely new pillar of genetic medicine.


RNAi: Nature Abhors a Double-Strand. György Hutvágner and Phillip D.Zamore in Current Opinion in Genetics & Development, Vol. 12, No. 2, pages 225–232; April 2002.Gene Silencing in Mammals by Small Interfering RNAs. Michael T.McManus and Phillip A. Sharp in Nature Reviews Genetics, Vol. 3, pages 737–747; October 2002.MicroRNAs: At the Root of Plant Development? Bonnie Bartel and David P.Bartel in Plant Physiology, Vol. 132, No. 2; pages 709–717; June 2003.Available at www.plantphysiol.org /cgi /content / full/132/2/709

M O R E T O E X P L O R E

THE MACHINERY for RNA interference was discovered to operate in mammals just two years ago. Yet about 10 companies, including thesampling below, have already begun testing ways to exploit gene censoring to treat or prevent human disease. —The Editors

COMPANY PROJECTS STATUS

Alnylam Pharmaceuticals Researching therapeutic applications of RNAi, Founded in 2002 by Bartel, Tuschl, Sharp and Cambridge, Mass. but specific disease targets not yet announced Zamore, the firm has secured initial funding

and several patents

Cenix Biosciences Investigating the use of RNAi-based therapies With Texas-based Ambion, Cenix is creating Dresden, Germany for cancer and viral diseases a library of siRNAs to cover the entire

human genome

Ribopharma Attempting to chemically modify siRNAs to make drugs Clinical trials in brain cancer patients Kulmbach, Germany for glioblastoma, pancreatic cancer and hepatitis C are expected to begin this year

Sirna Therapeutics Testing a catalytic RNA medicine for advanced Changed name from Ribozyme PharmaceuticalsBoulder, Colo. colon cancer in clinical trials; development of in April; recently secured $48 million

RNAi-based therapeutics is still in early stages in venture capital

Efforts to Apply RNA Interference to Medicine


For much of the past decade,policy leaders and social scientists havegrown increasingly concerned about a so-cietal split between those with and thosewithout access to computers and the In-ternet. The U.S. National Telecommuni-

cations and Information Ad-ministration popularized aterm for this situation in themid-1990s: the “digital di-

vide.” The phrase soon became used in aninternational context as well, to describethe status of information technology fromcountry to country.

Demystifying the

Digital DivideThe simple binary notion oftechnology haves and have-notsdoesn’t quite compute

By Mark Warschauer

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42 S C I E N T I F I C A M E R I C A N A U G U S T 2 0 0 3COPYRIGHT 2003 SCIENTIFIC AMERICAN, INC.

L E F T T O R I G H T : N A T I O N A L I N S T I T U T E O F I N F O R M A T I O N T E C H N O L O G Y , D A V I D G R E E D Y , P H O T O D I S C , P H O T O D I S C ( t o p r o w ) ; P H O T O D I S C ( a l l p h o t o g r a p h s i n s e c o n d r o w ) ; P H O T O D I S C , P H O T O D I S C , M A R K W A R S C H A U E R ( t h i r d r o w ) ; P H O T O D I S C , P H O T O D I S C , K E I T H D A N N E M I L L E R C o r b i s / S A B A ( f o u r t h r o w ) ; K E I T H D A N N E M I L L E R C o r b i s / S A B A , N A T I O N A L I N S T I T U T E O F I N F O R M A T I O N T E C H N O L O G Y , P H O T O D I S C , P H O T O D I S C ( f i f t h r o w ) ; P H O T O D I S C , P H O T O D I S C , V I V I A N M O O S C o r b i s ( b o t t o m r o w )


Underlying disparities are real, bothwithin and among countries. The BentonFoundation, which promotes the public-interest use of communications technolo-gy, reports that by late 2001, 80 percentof American families with annual house-hold income greater than $75,000 wereonline, compared with 25 percent of thepoorest U.S. families. Total home Inter-net access was 55 percent for whites, 31percent for African-Americans and 32percent for Hispanics. Looking at the in-ternational picture, in most African coun-tries less than 1 percent of the populationis online. Not surprisingly, such dispari-

ty correlates highly with other measuresof social and economic inequality.

Yet the simple binary description of adivide fails to do justice to the complexreality of various people’s differing accessand usage of digital technology. AnAmerican who surfs the Internet on acomputer at a local library once a monthmight be considered to be a digital “have-not,” whereas someone in a developingcountry with the same profile would be a“have.” Indeed, couching the conditionin black-and-white terminology can leadthose attempting to deal with technolog-ical inequities down the wrong path. Thelate Rob Kling, who directed the Centerfor Social Informatics at Indiana Univer-sity, put it well: “[The] big problem with

the ‘digital divide’ framing is that it tendsto connote ‘digital solutions,’” that is,“computers and telecommunications,”without a consideration of the contextinto which that hardware would be put.

This line of reasoning led some to as-sume that the dearth of digital access ofnations, communities and individualscould be easily tackled by an infusion ofcomputers and Internet connections. For-mer Speaker of the U.S. House of Repre-sentatives Newt Gingrich has talkedabout the virtues of giving every child alaptop computer, without offering a sol-id plan for using the devices. And Bill

Gates donated computers to small-townlibraries across America, believing thatInternet connections would help stem theexodus from rural areas. Although Inter-net connection through small-town li-braries has improved people’s lives by al-lowing them to stay in touch with friendsand relatives, it has not stemmed the ex-odus—which largely depends on broad-er factors, such as employment availabil-ity—and may even have contributed to itby allowing people to search for jobs incities. (To Gates’s and Gingrich’s credit,they at least had the issue of technologyaccess on their radar screens. Gates, rec-ognizing the limitations of computertechnology in solving social ills, has sincegone on to donate billions of dollars to

broader health and education campaignsaround the world.)

This perspective is known in academ-ic circles as technological determinism,the idea that the mere presence of tech-nology leads to familiar and standard ap-plications of that technology, which inturn bring about social change. The Har-vard Graduate School of Education’sChristopher Dede has termed this the“fire” model, with its implication that acomputer, by its mere presence, will gen-erate learning or development, just as afire generates warmth. Governments, theprivate sector, foundations and charities

have thus spent hundreds of millions ofdollars to bridge the perceived digital di-vide by providing computers and Inter-net lines to those in need, often withoutsufficient attention to the social contextsin which these technologies might beused. (Dede notes that a better modelthan fire might be clothing, which alsokeeps one warm yet is tailored for indi-vidual fit and use.)

How does this application based onthe assumption of technological deter-minism turn out in practice? Over thepast few years, I have traveled around theworld to study community technologyprograms in both developed and devel-oping countries. I have observed scores ofdiverse programs and have interviewedhundreds of participants and organizers.As the following case studies show, twobasics became apparent: well-intentionedprograms often lead in unexpected direc-tions, and the worst failures occur whenpeople attempt to address complex socialproblems with a narrow focus on provi-sion of equipment.

A Minimalist ApproachIN 1999 THE MUNICIPAL govern-ment of New Delhi, in collaboration withan Indian company called the NationalInstitute of Information Technology,


■ The concept of a “digital divide” separating those with access to computers andcommunications technology from those without is simplistic and can lead towell-meaning but incomplete attempts at a solution based on merely addingtechnology to a given circumstance.

■ In fact, people have widely varying opportunities for access to computers andcommunications technology and disparate reasons for wanting the level ofaccess they may desire.

■ A consideration of how people can use computers and the Internet to further theprocess of social inclusion is paramount in any effort to install new technologyinto an environment lacking it.

Overview/Technologic Logic

Some assumed that the dearth of digital access could be easily tackled by an infusion of computers.


launched an experiment to provide com-puter access to children in one of thecity’s poorest areas. Government officialsand representatives of the company setup an outdoor kiosk with several com-puter stations. The computers, with dial-up Internet access, were inside a lockedbooth, but the monitors, joysticks andbuttons stuck out through holes andwere accessible. In line with a conceptknown as minimally invasive education,the test included no teachers or instruc-tors. The idea was to allow the childrenunfettered daily access so they couldlearn at their own pace rather thanthrough the directives of adults.

The program was hailed by its orga-nizers as a groundbreaking model forhow to bring information technology tothe world’s urban poor. Inspiring storiescirculated on the Internet about how il-literate children taught themselves to usecomputers and thus crashed the barriersto the information age. These accountsled to additional kiosks being set up inother locations.

My visit to one of the New Delhikiosks, however, revealed a different pic-ture. The Internet connection seldomfunctioned. The architecture of thekiosk—based on a wall instead of aroom—made instruction or collaboration

difficult. Most poor communities in NewDelhi already have organizations thatwork with children and that could haveset up educational training at a differentkind of computer center, but their par-ticipation was neither solicited nor wel-comed. Over the nine-month duration ofthe experiment, the youngsters did in-deed learn how to manipulate the joy-stick and buttons. But without educa-tional programs and with the content pri-marily in English rather than Hindi, theymostly did what you might expect: playedgames and used paint programs to draw.

Neighborhood parents felt ambiva-lent. Several embraced the initiative, butmost expressed concern about the lack oforganized instruction. Some even com-plained that the computer was detrimen-tal. “My son used to be doing very wellin school,” one parent said, “but now hespends all his free time playing comput-er games at the kiosk, and his school-

work is suffering.” In short, the commu-nity came to realize that minimally inva-sive education was, in practice, minimal-ly effective education.

Nevertheless, an overemphasis onhardware with scant attention paid to thepedagogical and curricular frameworksthat shape how the computers are used iscommon in educational technology proj-ects throughout the world. But such tech-nological determinism has been chal-lenged in the academic arena by a con-cept called social informatics, whichargues that technology must be consid-ered within a specific context that in-cludes hardware, software, support re-sources, infrastructure, as well as peoplein various roles and relationships withone another and with other elements ofthe system. And the technology and so-cial system continuously shape each oth-er, like a biological community and itsenvironment.

Although grassroots teachers, parentsor aid workers may be unfamiliar withthe academic term “social informatics,”many already appreciate the implicationsof an interwoven relationship of technol-ogy and public organizations. Social in-formatics has recently given birth to“community informatics,” which alsoconsiders unique aspects of the particu-lar culture into which technology isplaced, so that communities can most ef-fectively use that technology to achievesocial, economic, political or culturalgoals.

A More Integrated AttemptONE EXAMPLE of a program based ona community informatics approach is theGyandoot (which translates to “purvey-or of knowledge”) project in India. In2000 in the southwest corner of MadhyaPradesh, one of India’s poorest states, thegovernment established this digital effort


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MARK WARSCHAUER is vice chair of the department of education at the University of Califor-nia, Irvine, and is also affiliated with the university’s School of Information and Computer Sci-ence and Center for Research on Information Technology and Organizations. He is the found-ing editor of Language Learning & Technology journal and author or editor of seven books ontechnology, education and development. The editor of the “Papyrus News” e-mail news listreporting on technology and society, Warschauer has conducted research in Egypt, China,India, Brazil, Singapore and other countries, focusing on how diverse peoples and commu-nities make use of information technology for human and social development.

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NEW DELHI CHILDREN experiment with what is literally a hole-in-the-wall computer in 2000. Theminimally invasive education project was designed to insert technology into the environment so thatthe children would learn to use the computer without guidance. Without direction, however, thecomputer proved for the most part to be merely a high-tech toy.


to bring more economic and politicalpower to the rural population, nearlytwo thirds of whom are undernourishedand illiterate. Each village received acomputer kiosk, which is connected tothe others in a network. Local entrepre-neurs service the machines, and a smallteam hired by the government createscontent for the Gyandoot intranet, basedon an analysis of the people’s social andeconomic needs.

This content includes updated pricesof popular crops at the district, regionaland national markets, so that small farm-ers can decide whether to harvest theircrop and where to sell it, without wast-ing a day traveling to the district capitalfor price checks. A complaint service letsvillagers report local problems, such asmalfunctioning hand pumps or teachersfailing to show up at schools. With vil-

lagers quickly able to voice such concernsdigitally, government services have start-ed to improve.

Local kiosk managers operate thecomputers, thus making the service,which costs a few cents per use, accessi-ble even to the illiterate. Kiosk managersalso offer computer training to villagechildren for a small fee, thereby uppingthe collective computer skills of the com-munity while affording additional in-come to the managers. And Gyandoot isused to connect with the area’s broadsocioeconomic initiatives, such as a“healthiest child” campaign, which pro-vides information about vaccinationsand nutrition.

Gyandoot was inexpensive to launch,because it involves only one computerper village, and it is partly self-sustaining,because kiosk operators are able to re-cover some of their costs through smallfees to users. With its emphasis on meet-ing user needs through small-scale, local-ly run services, it has much in commonwith the earlier model of telephone

kiosks that helped to extend phone ac-cess throughout much of India. In thenine months beginning in October 2001,the Gyandoot kiosks had some 21,300users, 80 percent of whom had annual in-comes of less than $300. The number ofusers is a small percentage of the popula-tion, but the benefits of the project, suchas improved government services, even-tually ripple outward to friends, familiesand co-workers.

The magnitude of the Gyandoot suc-cess story remains to be determined. Butthe underlying approach—a combinationof well-planned and low-cost infusions oftechnology with content developmentand educational campaigns targeted tosocial development—is surely a healthyalternative to projects that rely on plant-ing computers and waiting for somethingto grow.

Fine-Tuning in CaliforniaA DOMESTIC CASE, which I investigat-ed with doctoral candidate Jodie Wales,also shows the importance of the com-munity informatics approach. Californiahigh schools offer Advanced Placement(AP) courses that give students collegecredit and facilitate their admission to thebest universities. These courses are avail-able in dramatically unequal numbers,however, largely in relation to the socio-economic status and ethnicity of studentpopulations. For example, in 1999 Bev-erly Hills High School, which is 9 percentAfrican-American and Hispanic, offered45 AP classes. Inglewood High School, ina different part of the same metropolitanarea and with 97 percent black and His-panic students, offered only three suchcourses.

To address this problem, in 2000 theUniversity of California Office of the Pres-ident and the university’s College Prepa-ratory Initiative engaged in a collabora-tion with the Anaheim Union HighSchool District, which has a large His-

panic population. The first effort was anonline AP course in macroeconomics, be-cause many of their students, even thepoorer of them, had some access to com-puters and the Internet outside of school.Attendees of several schools enrolled inthe courses, thus potentially overcomingthe problem of small and dispersed pop-ulations of advanced students. The result:only six of 22 students completed thecourse. Some reasons became clearthrough student surveys and interviews.The online instructional format—withstudents completing work independentlyfrom their home computers—lacked suf-ficient structure, teacher contact and peerinteraction to maintain students’ motiva-tion to cope with the challenging materi-al. The Hispanic students commentedmost frequently that they preferred thesetypes of social support.

Still, the failure was fruitful. A revisedprogram the next year brought studentsfrom several schools to a computer labo-ratory at a central location, this time totake an honors course, “Introduction toComputer Science and the C Program-ming Language.” Although the class wasstill taught online to take advantage of thedistant expert instructor and the comput-er-based curriculum, a local teacherjoined the students to answer questionsand provide general assistance. The com-bination of online expert instruction andface-to-face teacher and peer interactionproved much more effective: 56 of 65 stu-dents completed the course. Based onthese results, the University of CaliforniaCollege Preparatory Initiative abandonedthe previous model of pure online in-struction in exchange for the combinedonline and face-to-face model. (Of course,students may find an honors computerclass somewhat more accessible than anAP macroeconomics course, or the formermight be better suited for the online set-ting. Such points must also be considered


The key issue is not unequal access to computers but rather the unequal ways that computers are used.


when devising the mode of instruction.)More and more evidence points to

the need for a careful consideration of allpotential ramifications before applyingtechnology as an educational Band-Aid.In fact, my research—together with thatof other educational investigators such asHenry J. Becker of the University of Cal-ifornia at Irvine, Harold Wenglinsky ofthe City University of New York andJanet Schofield of the University of Pitts-burgh—shows that computer use inschools is as likely to exacerbate in-equality as lessen it. The key issue is notunequal access to computers but ratherthe unequal ways that computers areused. Our studies note that kindergartenthrough 12th grade students who enjoya high socioeconomic status more fre-quently use computers for experimenta-tion, research and critical inquiry, where-as poor students engage in less challeng-ing drills and exercises that do not takefull advantage of computer technology.In mathematics and English classes,where such drills are common, poor stu-dents actually have more access to com-puters than do more affluent ones. Onlyin science classes, which rely on experi-

ments and simulations, do wealthy stu-dents use computers more. Once again, a“digital divide” framework that focuseson access issues alone fails to face thesebroader inequalities in technology useand learning.

Changing the Mind-setPEOPLE ACCESS digital information ina wide variety of ways and usually as partof social networks involving relatives,friends and co-workers. Literacy pro-vides a good analogy. Literacy does notexist in a bipolar divide between thosewho absolutely can and cannot read.There are levels of literacy for function-al, vocational, civic, literary and scholar-ly purposes. And people become literate

not just through physical access to booksbut through education, communication,work connections, family support andassistance from social networks. Similar-ly, technology can be well implementedto augment and improve existing socialefforts and programs.

The bottom line is that there is no bi-nary digital divide and no single overrid-ing factor for determining—or closing—

such a divide. Technology does not existas an external variable to be injectedfrom the outside to bring about certainresults. It is woven into social systemsand processes. And from a policy stand-point, the goal of bringing technology tomarginalized groups is not merely toovercome a technological divide but in-stead to further a process of social inclu-sion. Realizing this objective involves notonly providing computers and Internetlinks or shifting to online platforms butalso developing relevant content in di-verse languages, promoting literacy andeducation, and mobilizing communityand institutional support toward achiev-ing community goals. Technology thenbecomes a means, and often a powerfulone, rather than an end in itself.

It is important to note that the Bushadministration is cutting funding of pro-grams that foster access to technology.Some might argue that such cuts are ap-propriate if there is no digital divide, butthat reasoning is as specious as simplisticsolutions based on the notion of a divide.The opposite of divide is multiply. Policyplanners should stop thinking in terms ofdivides to be bridged. The combinationof carefully planned infusions of tech-nology with relevant content, improvededucation and enhanced social supportcan multiply those assets that communi-ties already have.


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Technology and Social Inclusion: Rethinking the Digital Divide. Mark Warschauer. MIT Press, 2003.Who’s Wired and Who’s Not? Henry J. Becker in The Future of Children, Vol. 10, No. 2; 2000. Available at www.futureofchildren.org/usr–doc/ vol10no2art3.pdfReconceptualizing the Digital Divide. Mark Warschauer in First Monday, Vol. 7, No. 7; 2002.Available at www.firstmonday.dk/issues/issue7–7/warschauer/Athena Alliance: www.athenaalliance.org/Center for Social Informatics: www.slis.indiana.edu/CSI/Community Informatics Research and Applications Unit: www.cira.org.uk /Community Technology Centers Network: www.ctcnet.orgDigital Divide Network: www.digitaldividenetwork.org/


FARMERS ACCESS the Gyandoot intranet at a community computer facility in central India’s Dhardistrict, where 60 percent of the 1.7 million residents live below the poverty line. The intranet providescrop prices, official application forms, and a place to hold village auctions and to air public grievances.


Long thought to be solely the BRAIN’S COORDINATOR of body movement,

THE CEREBELLUM is now known to be active during a wide variety of cognitive and perceptual activities


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“Lesser Brain”Rethinking

By James M. Bower and Lawrence M. Parsons

So began, somewhat modestly, the article thatin 1958 introduced the cerebellum to the read-ers of Scientific American. Written by Ray S.Snider of Northwestern University, the intro-duction continued, “In contrast to the cere-brum, where men have sought and found thecenters of so many vital mental activities, thecerebellum remains a region of subtle and tan-talizing mystery, its function hidden from in-vestigators.” But by the time the second Scien-tific American article on the cerebellum ap-peared 17 years later, author Rodolfo R. Llinás(currently at New York University MedicalCenter) confidently stated, “There is no longerany doubt that the cerebellum is a central con-trol point for the organization of movement.”

Recently, however, the cerebellum’s functionhas again become a subject of debate. In par-ticular, cognitive neuroscientists using powerfulnew tools of brain imaging have found that the

human cerebellum is active during a wide rangeof activities that are not directly related tomovement. Sophisticated cognitive studies havealso revealed that damage to specific areas ofthe cerebellum can cause unanticipated impair-ments in nonmotor processes, especially in howquickly and accurately people perceive sensoryinformation. Other findings indicate that thecerebellum may play important roles in short-term memory, attention, impulse control, emo-tion, higher cognition, the ability to scheduleand plan tasks, and possibly even in conditionssuch as schizophrenia and autism. Additionalneurobiological experiments—both on the pat-tern of sensory inputs to the cerebellum and onthe ways in which the cerebellum processes thatinformation—also suggest a need to substan-tially revise current thinking about the functionof this organ. The cerebellum has once again be-come an area of “tantalizing mystery.”

“In the back of our skulls, perched upon the brain stem underthe overarching mantle of the great hemispheres of thecerebrum, is a baseball-sized, bean-shaped lump of gray andwhite brain tissue. This is the cerebellum, the ‘lesser brain.’ ”


In retrospect, it is perhaps not sur-prising that the cerebellum acts as morethan just a simple controller of move-ment. Its great bulk and intricate structureimply that it has a more pervasive andcomplex role. It is second in size only tothe cerebral cortex, the wrinkled surfaceof the brain’s two large hemispheres,which is known to be the seat of manycritical brain functions. Like the humancerebral cortex, the cerebellum packs aprodigious amount of circuitry into asmall space by folding in on itself numer-ous times. Indeed, the human cerebellumis much more folded than the cerebral

cortex; in various mammals, it is the solefolded brain structure. Flattening out thehuman cerebellum yields a sheet with anaverage area of 1,128 square centime-ters—slightly larger than a record albumcover. That is more than half the 1,900square centimeters of the surface area ofthe two cerebral cortices added together.

The cerebellum clearly has an impor-tant job, because it has persisted—andbecome larger—during the course of evo-lution. Although biologists often consid-er the growth of the cerebral cortex to bethe defining characteristic of humanbrain evolution, the cerebellum has also

enlarged significantly, increasing in sizeat least three times during the past mil-lion years of human history, according tofossilized skulls. Perhaps the cerebellum’smost remarkable feature, however, isthat it contains more individual nervecells, or neurons, than the rest of thebrain combined. Furthermore, the waythose neurons are wired together has re-mained essentially constant over morethan 400 million years of vertebrate evo-lution [see box on opposite page]. Thus,a shark’s cerebellum has neurons that areorganized into circuits nearly identical tothose of a person’s.

More than MovementTHE HYPOTHESIS that the cerebellumcontrols movement was first proposed bymedical physiologists in the middle of the19th century, who observed that remov-ing the cerebellum could result in imme-diate difficulties in coordinating move-ment. During World War I, English neu-rologist Gordon Holmes added greatdetail to these early findings by going fromtent to tent on the front lines of battle anddocumenting the lack of motor coordina-tion in soldiers who had suffered gunshotor shrapnel wounds to the cerebellum.

In the past 15 years, however, morerefined testing techniques have made thestory more complicated. In 1989 RichardB. Ivry and Steven W. Keele of the Uni-versity of Oregon observed that patientswith cerebellar injuries cannot accuratelyjudge the duration of a particular soundor the amount of time that elapses be-tween two sounds. In the early 1990s re-searchers led by Julie A. Fiez of Washing-ton University observed that patients withdamage to the cerebellum were more er-ror-prone than others in performing cer-tain verbal tasks. One such individual, forinstance, required additional time tothink of an appropriate verb, such as “toshave,” when shown a picture of a razor,for example. He came up with a descrip-tor such as “sharp” more readily.

In more recent studies, the two of usdemonstrated that patients who haveneurodegenerative diseases that specifi-cally shrink the cerebellum are often lessaccurate than others in judging fine dif-ferences between the pitch of two tones.


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■ The cerebellum sits at the base of the brain and has a complex neural circuitry that has remained virtually the same throughout the evolution of animals with backbones.

■ The traditional notion that the cerebellum controls movement is being questionedby studies indicating that it is active during a wide variety of tasks. The cerebellummay be more involved in coordinating sensory input than in motor output.

■ Removing the cerebellum from young individuals often causes few obviousbehavioral difficulties, suggesting that the rest of the brain can learn to functionwithout a cerebellum.

Overview/The Cerebellum

LARGER THAN YOU’D THINKFLATTENING the outer layer, or cortex, of the two human cerebral hemispheres andthe cerebellum illustrates that the cerebellum has roughly the same surface area asa single cerebral hemisphere, even though when folded it takes up much less space.The size and complexity of the cerebellum indicate that it must play a crucial function.

Cerebral hemispheres

CerebellumFlattened leftcerebral cortex

Flattened right cerebral cortex

Flattenedcerebellum



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HOW THE CEREBELLUM IS WIREDTHE BASIC FEATURES of cerebellar circuitry have been knownsince the seminal work of Spanish neuroanatomist SantiagoRamón y Cajal in the late 1800s. The central neuron is thePurkinje cell, named for Czech physiologist Johannes E.Purkinje, who identified it in 1837. The Purkinje cell providesthe sole output of the cerebellar cortex and is one of thelargest neurons in the nervous system, receiving anextraordinary 150,000 to 200,000 inputs (synapses)—anorder of magnitude more than any single neuron in the cerebralcortex. These inputs spring principally from one of the smallestvertebrate neurons, the cerebellar granule cell. Granule cellsare packed together at a density of six million per squaremillimeter, making them the most numerous type of neuron in

the brain. The axon, or main trunk line carrying the outgoingsignal, of every granule cell rises vertically out of the granulecell layer, making multiple inputs with its overlying Purkinjecell. The axon then splits into two segments that stretch awayin opposite directions. These segments align into parallel fibersthat run through the arms, or dendrites, of a Purkinje cell likewires through an electrical pole, providing a single input tomany hundreds of Purkinje cells. Granule cells alsocommunicate with three other types of neurons—the stellate,basket and Golgi cells—which help to modulate the signalsemitted by both the granule and Purkinje cells. This basicpattern occurs in every cerebellum, indicating that it must beintegral to its function. —J.M.B. and L.M.P.

Stellate cell

Parallel fibers of granule cells

Purkinje cell dendrites

Purkinje cell

Golgi cell

Granulecells

Granule cells

Area of detail

Ascendinggranulecell axon

Basket cell


Similarly, Peter Thier of the University ofTübingen in Germany and his co-work-ers found that people with damage to, orshrinkage of, part or all of the cerebellumare prone to make errors in tests in whichthey are asked to detect the presence,speed and direction of moving patterns.In addition, Hermann Ackermann andhis collaborators, also at Tübingen, ob-served that patients with degeneratedcerebellums are less able than healthy per-sons to discriminate between the similar-sounding words “rabbit” and “rapid.”

The impairments experienced by peo-ple with cerebellar damage can extend be-yond language, vision and hearing. Jere-my D. Schmahmann of MassachusettsGeneral Hospital reported that adult andchild cerebellar patients have difficultymodulating their emotions: they eitherfail to react to or overreact to a stimulusthat elicits a more moderate responsefrom most people. Other researchers havedemonstrated that adults with cerebellardamage show delays and tend to makemistakes in spatial reasoning tests, such asdetermining whether the shapes of objectsseen from different views match. Somescientists have also tied the cerebellum todyslexia. Rod I. Nicolson and his col-leagues at the University of Sheffield inEngland, for instance, found that peoplewith dyslexia and those with cerebellardamage have similar deficits in learningability and that dyslexics have reducedcerebellar activity during certain tasks.

Other recent studies suggest that thecerebellum might be involved in workingmemory, attention, mental functions suchas planning and scheduling, and impulsecontrol. In 1992 Jordan Grafman and hisco-workers at the National Institutes ofHealth observed, for instance, that indi-

viduals with an atrophied cerebellum hadtrouble with the planning and schedulingof steps required to solve the Tower ofHanoi problem, in which rings of differ-ent sizes must be arranged on a series ofpegs according to specific rules. Two in-dependent neuroimaging studies con-ducted in 1997 reported that the cerebel-lum of healthy volunteers became activewhen they were asked to recall a list of let-ters they had heard recited moments ear-

lier or when they were instructed tosearch a pattern for a specific image. In2002 a brain imaging study by XavierCastellanos, Judith L. Rapoport and theircolleagues at the National Institute ofMental Health found that the cerebellumof children with attention-deficit hyper-activity disorder—which is characterizedby a lack of impulse control—is reducedin size. Finally, brain imaging studies ofhealthy people and animals indicate thatthe cerebellum is normally active duringsensory processes such as hearing, smell,thirst, need for food or air, awareness ofbody movement, and perception of pain.

Touching, FeelingWE ARE AMONG the researchers whohave become convinced that the tradi-tional motor-control theory of cerebellarfunction is inadequate to account for thenew data. We came to this conclusion ini-tially by intensively studying cerebellar re-


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JAMES M. BOWER and LAWRENCE M. PARSONS are both at the Research Imaging Center atthe University of Texas Health Science Center in San Antonio, where Bower is professor ofcomputational neurobiology and Parsons is professor of cognitive neuroscience. Bower—

who is also professor at the Cajal Neuroscience Center at the University of Texas at San An-tonio—is a founder of the Journal of Computational Neuroscience and of the internationalAnnual Computational Neuroscience Meeting. He has also had a long-standing involvementin science education and is one of the creators of a children’s educational Web site(Whyville.net). Parsons has been responsible for establishing a cognitive neuroscience pro-gram at the National Science Foundation. He is a founding member of the editorial boardof the journal Human Brain Mapping and serves as a trustee for the International Founda-tion for Music Research.

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THE CEREBELLUM’S FRACTURED NATUREA PARTICULAR AREA on a rat’s face is not represented as a single area in thecerebellum. When scientists use a probe to touch a rat’s lower lip, for instance, theycan record electrical activity at several widely spaced spots on the animal’scerebellar cortex. Such fragmentation may allow the cerebellum to integrate avariety of incoming sensory information obtained by different body parts during thecourse of exploration.

Representative area ofcerebellar cortex

Rat brain

Cerebellum

Front whiskersUpper lipInside mouthLower lip Top toothBottom tooth

KEY


gions that are active during touch. One ofus (Bower) began such work while a grad-uate student more than 20 years ago inthe laboratory of Wallace I. Welker at theUniversity of Wisconsin–Madison. Theseinvestigations used a technique calledmicromapping to record the electrical ac-tivity of small patches of neurons in thebrains of rats as they were touched light-ly on various parts of their bodies.

Such tactile stimuli evoked activityacross a large area of the cerebellum [seeillustration on opposite page]. What ismore, the map appeared fractured, withneighboring areas of the cerebellum oftenreceiving inputs from disparate regions ofthe body and with areas that were farapart being represented next to one an-other in the cerebellum. Such a mappingplan is very different from that occurring

in the cerebral cortex, where the spatial re-lations between areas of the body surfaceare retained in the cortical regions that re-spond to and send signals to those areas.

Although the fractured nature of thecerebellar maps is unusual, an even moresurprising finding was that the rat cerebel-lum receives input primarily from the faceof the animal. This was initially confusingbecause Snider had shown earlier that

most of the tactile region of the cat cere-bellum receives input from the forepawsand that the bulk of that region in mon-keys is active when the fingers are touched.

A Sensory CoordinatorGIVEN THE DIFFERENCES in the re-gions of the body surface represented inthe cerebellum of various types of animals,the question became: How is the mouth of

a rat like the forepaws of a cat or the fin-gers of a monkey? The conclusion fromthe Wisconsin studies appeared to be thateach structure is used by each animal tolearn about its environment throughtouch. Anyone with a cat knows howmuch mischief its paws can cause, andanyone familiar with children recognizeshow actively—and sometimes painfully—

little fingers are used to gain information

about the youngsters’ immediate world.But rats tend to get into trouble using theirmouths. The fractured structure of thetouch maps in the cerebellum supportedthe idea that the region was somehowcomparing the sensory data coming fromthe multiple body parts used by each ani-mal to explore its world. These mapsseemed to be organized according to theuse of the body parts rather than on theirabsolute proximity on the body surface.The idea that the rat cerebellum wassomehow comparing the sensory infor-mation coming from different parts of theface was further supported by models andexperiments examining how the cerebel-lum responded to these inputs. Whatemerged was a new hypothesis of cerebel-lar function suggesting that the cerebellumwas specifically involved in coordinatingthe brain’s acquisition of sensory data.

Although proposing novel ideas ofbrain function is easy, having the ideasaccepted in a field that had decided in the1850s that the cerebellum was a motorstructure is a different story. In this case,the task was made even harder by the factthat there is clearly an extremely closelinkage between sensory and motor sys-tems in the brain, especially those in-volving touch. To make sure that wewere seeing the effects of only sensory—

and not motor—activity, we needed tostudy people, who, unlike rats, can fol-low explicit instructions about when tomove and when not to. It was at thispoint that the partnership between thetwo of us began. In collaboration withPeter T. Fox of the University of Texas


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The cerebellum is more involved in SENSORY than in PURE MOTOR FUNCTION.

RUDOLF VAN’T HOFF of Howard County, Maryland, has cerebellar damage caused by type 1spinocerebellar atrophy, a rare genetic disease that usually manifests itself in middle age. Thedisorder has affected van’t Hoff’s balance, speech, and coordination and has also impaired his ability todiscriminate between some sounds. He steadies his body with a bungee cord when sitting on his tractor.


Health Science Center in San Antonio,we designed a neuroimaging study tocompare the amount of cerebellar activ-ity induced when volunteers were in-structed to use their fingers for a sensorytouch discrimination task or told just topick up and drop small objects. Under allprevious theories of cerebellar function,the fine finger motor control required inpicking up and dropping the small ob-jects would be predicted to induce largeamounts of cerebellar activity in the areaassociated with touch. Instead we foundvery little cerebellar activity in that region

during the pick-up-and-drop task, where-as sensory exploration using the fingerscaused an intense cerebellar response [seebox above]. This observation added sup-port to our idea that the cerebellum ismore involved in sensory than pure mo-tor function and in particular that it ishighly active during the process of ac-quiring sensory data.

Life without a CerebellumOUR SENSORY-ACQUISITION hypoth-esis is but one of several new theories aris-ing as a consequence of the growing evi-

dence for cerebellar involvement in morethan just motor control. In many cases,the new data have been accommodated bysimply broadening existing motor theoriesto account for nonmotor results. Ivry, forinstance, has advocated a “generalizedtiming” hypothesis of cerebellar functionthat suggests that the cerebellum controlsthe timing of body movements (such as co-ordinating changes in joint angles) to al-low individuals to time the duration ofsensory inputs such as sights and sounds.

Other researchers have posited thatthe cerebellum not only facilitates fine


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PROBING CEREBELLAR FUNCTION

TO DISCRIMINATE BETWEEN the cerebellum’spossible roles in coordinating movement andintegrating sensory input, we devised a four-part experiment. We used a technique calledfunctional magnetic resonance imaging toreveal brain activity in the cerebellum of sixhealthy people while they were either sensing astimulus on their fingers without moving them orpicking up and dropping small objects. In thefirst scenario, we immobilized a subject’s handsand rubbed pieces of sandpaper gently acrosstheir fingertips (a). Sometimes they were askedto compare the coarseness of two differenttypes of sandpaper (b). Both were purelysensory tasks, but the latter one required eachperson to discriminate between what they werefeeling on each hand.

The second scenario involved both sensoryand motor aspects. A volunteer placed his or herhands into separate bags that contained smallwooden balls of different shapes and textures. In the first task (c), the person was told torandomly pick up and drop the balls, paying littleheed to their shapes. In the second task (d), theindividual was asked to compare the shape andfeel of two balls every time he or she picked oneup in each hand.

The cerebellum showed very little activityduring the task that simply required picking upand dropping balls (c). In general, it was mostactive when the subjects were evaluating whatthey were sensing, either while moving (d) or still (b). These findings and others support ourhypothesis that the cerebellum’s main role is inprocessing sensory information rather than incontrolling movement. —J.M.B. and L.M.P.

PASSIVE SENSINGNo movement

ACTIVE SENSORY COMPARISONNo movement

Movement

Cerebellum Active area

Movement

a

c

b

d

Finesandpaper

Coarsesandpaper


movement but also “smooths” the pro-cessing of information related to moodand thought. Schmahmann expressedsuch a view in 1991, and in 1996 NancyC. Andreason of the University of Iowaadapted the hypothesis to schizophrenia.She maintains that cerebellar deficits couldunderlie the disordered mental functioncharacteristic of the disease. Other scien-tists have proposed that the regions of thecerebellum that have expanded dramat-ically during human evolution providecomputational support for psychologi-cal tasks that can be offloaded from the

cerebral cortex when it is overburdened.As the number of conditions that in-

volve changes in cerebellar activity hasgrown, researchers have attributed moreand more functions to the cerebellum. Butscientists must yet explain how a singlebrain structure whose neural circuitry isorganized into a uniform, repetitive pat-tern can play such an integral role in somany disparate functions and behaviors.

What is even more confounding is thatpeople can recover from cerebellar injury.Although total removal of the cerebelluminitially disrupts movement coordination,individuals (particularly young ones) can,with sufficient time, regain normal func-tion to a considerable degree. Such plas-ticity is a general characteristic of thebrain, but similar damage to primary sen-sory or motor-control regions of the cere-bral cortex usually leaves animals and hu-mans severely and permanently impairedin specific functions.

The capacity to recover from removalof the cerebellum has led some researchersto propose facetiously that its functionmight be to compensate for its own ab-sence. It is highly unlikely, however, thatsuch a large and intricate structure as thecerebellum is functionless or vestigial. In-stead cerebellar function appears to per-mit the rest of the brain to compensate toa considerable degree for its absence.

Few cerebellar theories, includingthose based on motor control, have pro-vided an explanation for this puzzling re-silience. In our view, the ability of thebrain to compensate for the cerebellum’sabsence implies a general and subtle sup-port function. Under the sensory coordi-nation hypothesis we favor, the cerebel-lum is not responsible for any particularovert behavior or psychological process.Rather it functions as a support structurefor the rest of the brain. That support in-volves monitoring incoming sensory dataand making continuous, very fine adjust-

ments in how that information is ac-quired—the objective being to assure thehighest possible quality of sensory input.

We predict that those adjustmentstake the form of extremely subtle changesin the positions of probing human fingersor rat whiskers or in the retina or the innerear. As a support structure, the cerebellumwould be expected to have some level ofactivity in a large number of conditions,especially those requiring careful controlof incoming and perhaps rememberedsensory data. Other brain systems canusually compensate for the lack of senso-ry data coordination through the use ofalternative processing strategies if thecerebellum is damaged or removed.

Indeed, motor coordination studiessuggest that people with cerebellar dam-age slow down and simplify their move-ments—reasonable strategies to compen-sate for a lack of high-quality sensorydata. An interesting and important exten-sion of this idea is that the continued op-

eration of a faulty cerebellum would havemore serious consequences than its com-plete removal. Although other brain struc-tures can compensate for the outright lackof sensory data control, ongoing faultycontrol would be expected to cause con-tinuing dysfunction in other brain regionsattempting to use bad data. This type ofeffect might explain the recent implica-tions for cerebellar involvement in disor-ders such as autism, in which patients failto respond to incoming sensory data.

Hypotheses such as ours carry a usefulreminder for future research: the presence

of activity in a brain area does not neces-sarily mean that it is directly involved in aparticular behavior or psychological pro-cess. Most of the machinery under thehood of a car, by analogy, is there to sup-port the function of the engine. One couldgenerate all kinds of hypotheses about therole of the radiator in propulsion—by cor-relating increased temperature to milesper hour, for instance, or by observingthat a car ceases to run if its radiator is re-moved. But the radiator is not the engine.

If the cerebellum is primarily a sup-port structure, then it does not contributedirectly to motor coordination, memory,perception, attention, spatial reasoningor any of the many other functions re-cently proposed. Although this theory isone of several competing to account forthe new and surprising data about thecerebellum, it is clear that how we thinkabout this brain structure—and there-fore how we conceive of the brain as awhole—is about to change.


The Role of the Cerebellum in Motor Control and Perception. Michael G. Paulin in Brain Behaviorand Evolution, Vol. 41, pages 39–50; February 1993.

The Cerebellum and Cognition. Edited by Jeremy D. Schmahmann. Academic Press, 1997.

Cerebellar Contributions to Cognition and Imagery. Richard B. Ivry and Julie A. Fiez in New Cognitive Neurosciences. Edited by Michael S. Gazzaniga. MIT Press, 2000.

The Cerebellum: Recent Developments in Cerebellar Research. Edited by Stephen M. Highsteinand W. Thomas Thatch. New York Academy of Sciences, 2002.


It is clear that how we think about this brain structure—and how we CONCEIVE OF THE BRAIN

as a whole—is about to change.


Informationin the

HOLOGRAPHIC UNIVERSE

Theoretical results about

black holes suggest that

the universe could be like

a gigantic hologram

By Jacob D. Bekenstein

Illustrations by Alfred T. Kamajian


Yet if we have learned anything from engi-neering, biology and physics, information isjust as crucial an ingredient. The robot at theautomobile factory is supplied with metaland plastic but can make nothing usefulwithout copious instructions telling it whichpart to weld to what and so on. A ribosomein a cell in your body is supplied with aminoacid building blocks and is powered by en-ergy released by the conversion of ATP toADP, but it can synthesize no proteins with-out the information brought to it from theDNA in the cell’s nucleus. Likewise, a cen-tury of developments in physics has taughtus that information is a crucial player inphysical systems and processes. Indeed, acurrent trend, initiated by John A. Wheelerof Princeton University, is to regard thephysical world as made of information, withenergy and matter as incidentals.

This viewpoint invites a new look at ven-erable questions. The information storagecapacity of devices such as hard disk driveshas been increasing by leaps and bounds.When will such progress halt? What is theultimate information capacity of a devicethat weighs, say, less than a gram and can fitinside a cubic centimeter (roughly the size ofa computer chip)? How much information

S C I E N T I F I C A M E R I C A N 59

Ask anybody whatthe physical worldis made of, and youare likely to be told“matter and energy.”


does it take to describe a whole universe?Could that description fit in a computer’smemory? Could we, as William Blakememorably penned, “see the world in agrain of sand,” or is that idea no morethan poetic license?

Remarkably, recent developments intheoretical physics answer some of thesequestions, and the answers might be im-portant clues to the ultimate theory of re-ality. By studying the mysterious proper-ties of black holes, physicists have de-duced absolute limits on how muchinformation a region of space or a quan-tity of matter and energy can hold. Relat-ed results suggest that our universe, whichwe perceive to have three spatial dimen-sions, might instead be “written” on atwo-dimensional surface, like a holo-gram. Our everyday perceptions of theworld as three-dimensional would thenbe either a profound illusion or merelyone of two alternative ways of viewing re-ality. A grain of sand may not encompassour world, but a flat screen might.

A Tale of Two EntropiesFORMAL INFORMATION theory orig-inated in seminal 1948 papers by Ameri-can applied mathematician Claude E.Shannon, who introduced today’s mostwidely used measure of information con-tent: entropy. Entropy had long been acentral concept of thermodynamics, thebranch of physics dealing with heat. Ther-modynamic entropy is popularly de-scribed as the disorder in a physical sys-tem. In 1877 Austrian physicist LudwigBoltzmann characterized it more precise-ly in terms of the number of distinct mi-

croscopic states that the particles com-posing a chunk of matter could be inwhile still looking like the same macro-scopic chunk of matter. For example, forthe air in the room around you, onewould count all the ways that the indi-vidual gas molecules could be distributedin the room and all the ways they couldbe moving.

When Shannon cast about for a wayto quantify the information contained in,say, a message, he was led by logic to aformula with the same form as Boltz-mann’s. The Shannon entropy of a mes-sage is the number of binary digits, or bits,needed to encode it. Shannon’s entropydoes not enlighten us about the value ofinformation, which is highly dependenton context. Yet as an objective measureof quantity of information, it has beenenormously useful in science and tech-nology. For instance, the design of everymodern communications device—fromcellular phones to modems to compact-disc players—relies on Shannon entropy.

Thermodynamic entropy and Shan-non entropy are conceptually equivalent:the number of arrangements that arecounted by Boltzmann entropy reflectsthe amount of Shannon information onewould need to implement any particulararrangement. The two entropies have twosalient differences, though. First, the ther-modynamic entropy used by a chemist ora refrigeration engineer is expressed inunits of energy divided by temperature,whereas the Shannon entropy used by acommunications engineer is in bits, es-sentially dimensionless. That difference ismerely a matter of convention.

Even when reduced to common units,however, typical values of the two en-tropies differ vastly in magnitude. A sili-con microchip carrying a gigabyte ofdata, for instance, has a Shannon entropyof about 1010 bits (one byte is eight bits),tremendously smaller than the chip’s ther-modynamic entropy, which is about 1023

bits at room temperature. This discrep-ancy occurs because the entropies arecomputed for different degrees of free-dom. A degree of freedom is any quanti-ty that can vary, such as a coordinatespecifying a particle’s location or onecomponent of its velocity. The Shannonentropy of the chip cares only about theoverall state of each tiny transistor etchedin the silicon crystal—the transistor is onor off; it is a 0 or a 1—a single binary de-gree of freedom. Thermodynamic en-tropy, in contrast, depends on the statesof all the billions of atoms (and theirroaming electrons) that make up eachtransistor. As miniaturization brings clos-er the day when each atom will store onebit of information for us, the useful Shan-non entropy of the state-of-the-art mi-crochip will edge closer in magnitude toits material’s thermodynamic entropy.When the two entropies are calculated forthe same degrees of freedom, they areequal.

What are the ultimate degrees of free-dom? Atoms, after all, are made of elec-trons and nuclei, nuclei are agglomera-tions of protons and neutrons, and thosein turn are composed of quarks. Manyphysicists today consider electrons andquarks to be excitations of superstrings,which they hypothesize to be the mostfundamental entities. But the vicissitudesof a century of revelations in physics warnus not to be dogmatic. There could bemore levels of structure in our universethan are dreamt of in today’s physics.

One cannot calculate the ultimate in-formation capacity of a chunk of matteror, equivalently, its true thermodynamicentropy, without knowing the nature ofthe ultimate constituents of matter or ofthe deepest level of structure, which Ishall refer to as level X. (This ambiguitycauses no problems in analyzing practi-cal thermodynamics, such as that of car


■ An astonishing theory called the holographic principle holds that the universeis like a hologram: just as a trick of light allows a fully three-dimensional imageto be recorded on a flat piece of film, our seemingly three-dimensional universecould be completely equivalent to alternative quantum fields and physical laws“painted” on a distant, vast surface.

■ The physics of black holes—immensely dense concentrations of mass—providesa hint that the principle might be true. Studies of black holes show that, althoughit defies common sense, the maximum entropy or information content of anyregion of space is defined not by its volume but by its surface area.

■ Physicists hope that this surprising finding is a clue to the ultimate theory of reality.

Overview/The World as a Hologram


engines, for example, because the quarkswithin the atoms can be ignored—theydo not change their states under the rel-atively benign conditions in the engine.)Given the dizzying progress in miniatur-ization, one can playfully contemplate aday when quarks will serve to store in-formation, one bit apiece perhaps. Howmuch information would then fit into ourone-centimeter cube? And how much ifwe harness superstrings or even deeper,yet undreamt of levels? Surprisingly, de-velopments in gravitation physics in thepast three decades have supplied someclear answers to what seem to be elusivequestions.

Black Hole ThermodynamicsA CENTRAL PLAYER in these develop-ments is the black hole. Black holes are aconsequence of general relativity, AlbertEinstein’s 1915 geometric theory of grav-itation. In this theory, gravitation arisesfrom the curvature of spacetime, whichmakes objects move as if they were pulledby a force. Conversely, the curvature is

caused by the presence of matter and en-ergy. According to Einstein’s equations, asufficiently dense concentration of matteror energy will curve spacetime so ex-tremely that it rends, forming a blackhole. The laws of relativity forbid any-thing that went into a black hole fromcoming out again, at least within the clas-sical (nonquantum) description of thephysics. The point of no return, called theevent horizon of the black hole, is of cru-cial importance. In the simplest case, thehorizon is a sphere, whose surface area islarger for more massive black holes.

It is impossible to determine what isinside a black hole. No detailed informa-tion can emerge across the horizon andescape into the outside world. In disap-

pearing forever into a black hole, howev-er, a piece of matter does leave sometraces. Its energy (we count any mass asenergy in accordance with Einstein’s E =mc2) is permanently reflected in an incre-ment in the black hole’s mass. If the mat-ter is captured while circling the hole, itsassociated angular momentum is addedto the black hole’s angular momentum.Both the mass and angular momentum ofa black hole are measurable from their ef-fects on spacetime around the hole. In thisway, the laws of conservation of energyand angular momentum are upheld byblack holes. Another fundamental law,the second law of thermodynamics, ap-pears to be violated.

The second law of thermodynamicssummarizes the familiar observation thatmost processes in nature are irreversible:a teacup falls from the table and shatters,but no one has ever seen shards jump upof their own accord and assemble into ateacup. The second law of thermody-namics forbids such inverse processes. Itstates that the entropy of an isolated phys-ical system can never decrease; at best, en-tropy remains constant, and usually it in-creases. This law is central to physicalchemistry and engineering; it is arguablythe physical law with the greatest impactoutside physics.

As first emphasized by Wheeler, whenmatter disappears into a black hole, its en-tropy is gone for good, and the secondlaw seems to be transcended, made irrel-evant. A clue to resolving this puzzle camein 1970, when Demetrious Christodou-lou, then a graduate student of Wheeler’sat Princeton, and Stephen W. Hawking ofthe University of Cambridge indepen-dently proved that in various processes,such as black hole mergers, the total areaof the event horizons never decreases. Theanalogy with the tendency of entropy toincrease led me to propose in 1972 that ablack hole has entropy proportional to


JACOB D. BEKENSTEIN has contributed to the foundation of black hole thermodynamics andto other aspects of the connections between information and gravitation. He is Polak Pro-fessor of Theoretical Physics at the Hebrew University of Jerusalem, a member of the IsraelAcademy of Sciences and Humanities, and a recipient of the Rothschild Prize. Bekensteindedicates this article to John Archibald Wheeler (his Ph.D. supervisor 30 years ago). Wheel-er belongs to the third generation of Ludwig Boltzmann’s students: Wheeler’s Ph.D. advis-er, Karl Herzfeld, was a student of Boltzmann’s student Friedrich Hasenöhrl.

THE

AU

THO

R

THE ENTROPY OF A BLACK HOLE is proportional to the area of its event horizon, the surface withinwhich even light cannot escape the gravity of the hole. Specifically, a hole with a horizon spanningA Planck areas has A⁄4 units of entropy. (The Planck area, approximately 10–66 square centimeter,is the fundamental quantum unit of area determined by the strength of gravity, the speed of lightand the size of quanta.) Considered as information, it is as if the entropy were written on theevent horizon, with each bit (each digital 1 or 0) corresponding to four Planck areas.

One Planck areaBlack holeevent horizon

One unit of entropy


the area of its horizon [see illustration onpreceding page]. I conjectured that whenmatter falls into a black hole, the increasein black hole entropy always compensatesor overcompensates for the “lost” en-tropy of the matter. More generally, thesum of black hole entropies and the ordi-nary entropy outside the black holes can-not decrease. This is the generalized sec-ond law—GSL for short.

The GSL has passed a large number ofstringent, if purely theoretical, tests.When a star collapses to form a blackhole, the black hole entropy greatly ex-ceeds the star’s entropy. In 1974 Hawk-ing demonstrated that a black hole spon-taneously emits thermal radiation, now

known as Hawking radiation, by a quan-tum process [see “The Quantum Me-chanics of Black Holes,” by Stephen W.Hawking; Scientific American, Janu-ary 1977]. The Christodoulou-Hawkingtheorem fails in the face of this phenom-enon (the mass of the black hole, andtherefore its horizon area, decreases), butthe GSL copes with it: the entropy of theemergent radiation more than compen-sates for the decrement in black hole en-tropy, so the GSL is preserved. In 1986Rafael D. Sorkin of Syracuse Universityexploited the horizon’s role in barring in-formation inside the black hole from in-fluencing affairs outside to show that theGSL (or something very similar to it) must

be valid for any conceivable process thatblack holes undergo. His deep argumentmakes it clear that the entropy enteringthe GSL is that calculated down to levelX, whatever that level may be.

Hawking’s radiation process allowedhim to determine the proportionality con-stant between black hole entropy andhorizon area: black hole entropy is pre-cisely one quarter of the event horizon’sarea measured in Planck areas. (ThePlanck length, about 10–33 centimeter, isthe fundamental length scale related togravity and quantum mechanics. ThePlanck area is its square.) Even in ther-modynamic terms, this is a vast quantityof entropy. The entropy of a black hole


LAU

RIE

GR

ACE

(g

rap

h)

THE THERMODYNAMICS OF BLACK HOLES allows one todeduce limits on the density of entropy or informationin various circumstances.

The holographic bound defines how muchinformation can be contained in a specified region ofspace. It can be derived by considering a roughlyspherical distribution of matter that is contained withina surface of area A. The matter is induced to collapse toform a black hole (a). The black hole’s area must besmaller than A, so its entropy must be less than A⁄4

[see illustration on preceding page]. Because entropycannot decrease, one infers that the original distrib-ution of matter also must carry less than A⁄4 units ofentropy or information. This result—that the maximuminformation content of a region of space is fixed by itsarea—defies the commonsense expectation that thecapacity of a region should depend on its volume.

The universal entropy bound defines how muchinformation can be carried by a mass m of diameter d.It is derived by imagining that a capsule of matter isengulfed by a black hole not much wider than it (b). Theincrease in the black hole’s size places a limit on howmuch entropy the capsule could have contained. Thislimit is tighter than the holographic bound, exceptwhen the capsule is almost as dense as a black hole (in which case the two bounds are equivalent).

The holographic and universal information boundsare far beyond the data storage capacities of anycurrent technology, and they greatly exceed thedensity of information on chromosomes and thethermodynamic entropy of water (c). —J.D.B.

Surface area ABlack hole

Mass m is sucked into black hole

Mass M

Diameter d

LIMITS ON INFORMATION DENSITY

Mass M + m

a

b

c

Size (centimeters)

Info

rmat

ion

Capa

city

(bits

)

Human chromosome Music CD

Library of Congress

Liter of water(thermodynamic entropy)

Universal entropy bound(for an object with density of water)

Holographic bound

Internet

10.01 100 104

1060

1070

1050

1040

1030

1020

1010

110– 4 106 108


one centimeter in diameter would beabout 1066 bits, roughly equal to the ther-modynamic entropy of a cube of water 10billion kilometers on a side.

The World as a HologramTHE GSL ALLOWS US to set bounds onthe information capacity of any isolatedphysical system, limits that refer to the in-formation at all levels of structure downto level X. In 1980 I began studying thefirst such bound, called the universal en-tropy bound, which limits how much en-tropy can be carried by a specified massof a specified size [see box on oppositepage]. A related idea, the holographicbound, was devised in 1995 by LeonardSusskind of Stanford University. It lim-its how much entropy can be containedin matter and energy occupying a speci-fied volume of space.

In his work on the holographic bound,Susskind considered any approximatelyspherical isolated mass that is not itself ablack hole and that fits inside a closed sur-face of area A. If the mass can collapse toa black hole, that hole will end up with ahorizon area smaller than A. The blackhole entropy is therefore smaller than A⁄ 4.According to the GSL, the entropy of thesystem cannot decrease, so the mass’soriginal entropy cannot have been biggerthan A⁄ 4. It follows that the entropy of anisolated physical system with boundaryarea A is necessarily less than A⁄ 4. What ifthe mass does not spontaneously col-lapse? In 2000 I showed that a tiny blackhole can be used to convert the system toa black hole not much different from theone in Susskind’s argument. The bound is

therefore independent of the constitutionof the system or of the nature of level X.It just depends on the GSL.

We can now answer some of those elu-sive questions about the ultimate limits ofinformation storage. A device measuringa centimeter across could in principle holdup to 1066 bits—a mind-boggling amount.The visible universe contains at least10100

bits of entropy, which could in principlebe packed inside a sphere a tenth of alight-year across. Estimating the entropyof the universe is a difficult problem, how-ever, and much larger numbers, requiringa sphere almost as big as the universe it-self, are entirely plausible.

But it is another aspect of the holo-graphic bound that is truly astonishing.Namely, that the maximum possible en-tropy depends on the boundary area in-stead of the volume. Imagine that we arepiling up computer memory chips in a bigheap. The number of transistors—the to-tal data storage capacity—increases withthe volume of the heap. So, too, does thetotal thermodynamic entropy of all thechips. Remarkably, though, the theoreti-cal ultimate information capacity of thespace occupied by the heap increases onlywith the surface area. Because volume in-creases more rapidly than surface area, atsome point the entropy of all the chipswould exceed the holographic bound. Itwould seem that either the GSL or ourcommonsense ideas of entropy and infor-mation capacity must fail. In fact, whatfails is the pile itself: it would collapse un-der its own gravity and form a black holebefore that impasse was reached. There-after each additional memory chip would

increase the mass and surface area of theblack hole in a way that would continueto preserve the GSL.

This surprising result—that informa-tion capacity depends on surface area—

has a natural explanation if the holo-graphic principle (proposed in 1993 byNobelist Gerard ’t Hooft of the Univer-sity of Utrecht in the Netherlands andelaborated by Susskind) is true. In theeveryday world, a hologram is a specialkind of photograph that generates a fullthree-dimensional image when it is illu-minated in the right manner. All the in-formation describing the 3-D scene is en-coded into the pattern of light and darkareas on the two-dimensional piece offilm, ready to be regenerated. The holo-graphic principle contends that an ana-logue of this visual magic applies to thefull physical description of any system oc-cupying a 3-D region: it proposes that an-other physical theory defined only on the2-D boundary of the region completelydescribes the 3-D physics. If a 3-D systemcan be fully described by a physical theo-ry operating solely on its 2-D boundary,one would expect the information con-tent of the system not to exceed that of thedescription on the boundary.

A Universe Painted on Its BoundaryCAN WE APPLY the holographic prin-ciple to the universe at large? The realuniverse is a 4-D system: it has volumeand extends in time. If the physics of ouruniverse is holographic, there would bean alternative set of physical laws, oper-ating on a 3-D boundary of spacetime


THE INFORMATION CONTENT of a pile of computer chips increases in proportionwith the number of chips or, equivalently, the volume they occupy. That simplerule must break down for a large enough pile of chips because eventually theinformation would exceed the holographic bound, which depends on thesurface area, not the volume. The “breakdown” occurs when theimmense pile of chips collapses to form a black hole.


somewhere, that would be equivalent toour known 4-D physics. We do not yetknow of any such 3-D theory that worksin that way. Indeed, what surface shouldwe use as the boundary of the universe?One step toward realizing these ideas isto study models that are simpler than ourreal universe.

A class of concrete examples of theholographic principle at work involvesso-called anti–de Sitter spacetimes. Theoriginal de Sitter spacetime is a model uni-verse first obtained by Dutch astronomerWillem de Sitter in 1917 as a solution ofEinstein’s equations, including the repul-sive force known as the cosmological con-stant. De Sitter’s spacetime is empty, ex-pands at an accelerating rate and is veryhighly symmetrical. In 1997 astronomersstudying distant supernova explosionsconcluded that our universe now expandsin an accelerated fashion and will proba-bly become increasingly like a de Sitterspacetime in the future. Now, if the re-pulsion in Einstein’s equations is changedto attraction, de Sitter’s solution turnsinto the anti–de Sitter spacetime, whichhas equally as much symmetry. More im-portant for the holographic concept, itpossesses a boundary, which is located“at infinity” and is a lot like our everydayspacetime.

Using anti–de Sitter spacetime, the-orists have devised a concrete exampleof the holographic principle at work: auniverse described by superstring theoryfunctioning in an anti–de Sitter space-time is completely equivalent to a quan-tum field theory operating on the bound-ary of that spacetime [see box above].Thus, the full majesty of superstring the-ory in an anti–de Sitter universe is paint-ed on the boundary of the universe. JuanMaldacena, then at Harvard University,first conjectured such a relation in 1997for the 5-D anti–de Sitter case, and it waslater confirmed for many situations byEdward Witten of the Institute for Ad-vanced Study in Princeton, N.J., andSteven S. Gubser, Igor R. Klebanov andAlexander M. Polyakov of PrincetonUniversity. Examples of this holograph-ic correspondence are now known forspacetimes with a variety of dimensions.

This result means that two ostensiblyvery different theories—not even actingin spaces of the same dimension—areequivalent. Creatures living in one of theseuniverses would be incapable of deter-mining if they inhabited a 5-D universedescribed by string theory or a 4-D onedescribed by a quantum field theory ofpoint particles. (Of course, the structuresof their brains might give them an over-

whelming “commonsense” prejudice infavor of one description or another, injust the way that our brains construct aninnate perception that our universe hasthree spatial dimensions; see the illustra-tion on the opposite page.)

The holographic equivalence can al-low a difficult calculation in the 4-Dboundary spacetime, such as the behaviorof quarks and gluons, to be traded for an-other, easier calculation in the highly sym-metric, 5-D anti–de Sitter spacetime. Thecorrespondence works the other way,too. Witten has shown that a black holein anti–de Sitter spacetime corresponds tohot radiation in the alternative physicsoperating on the bounding spacetime.The entropy of the hole—a deeply myste-rious concept—equals the radiation’s en-tropy, which is quite mundane.

The Expanding UniverseHIGHLY SYMMETRIC and empty, the5-D anti–de Sitter universe is hardly likeour universe existing in 4-D, filled withmatter and radiation, and riddled with vi-olent events. Even if we approximate ourreal universe with one that has matter andradiation spread uniformly throughout,we get not an anti–de Sitter universe butrather a “Friedmann-Robertson-Walker”universe. Most cosmologists today concur


TWO UNIVERSES of different dimension andobeying disparate physical laws are renderedcompletely equivalent by the holographicprinciple. Theorists have demonstrated thisprinciple mathematically for a specific type offive-dimensional spacetime (“anti–de Sitter”)and its four-dimensional boundary. In effect, the5-D universe is recorded like a hologram on the 4-D surface at its periphery. Superstring theoryrules in the 5-D spacetime, but a so-calledconformal field theory of point particles operates on the 4-D hologram. A black hole in the 5-D spacetime is equivalent to hot radiationon the hologram—for example, the hole and theradiation have the same entropy even thoughthe physical origin of the entropy is completelydifferent for each case. Although these twodescriptions of the universe seem utterlyunalike, no experiment could distinguishbetween them, even in principle. —J.D.B.

5-Dimensional anti–de Sitter spacetime

Superstrings

Conformal fields Hot radiation

4-Dimensional flat spacetime(hologram)

Black hole

A HOLOGRAPHIC SPACETIME


that our universe resembles an FRW uni-verse, one that is infinite, has no boundaryand will go on expanding ad infinitum.

Does such a universe conform to theholographic principle or the holographicbound? Susskind’s argument based oncollapse to a black hole is of no help here.Indeed, the holographic bound deducedfrom black holes must break down in auniform expanding universe. The entropyof a region uniformly filled with matterand radiation is truly proportional to itsvolume. A sufficiently large region willtherefore violate the holographic bound.

In 1999 Raphael Bousso, then at Stan-ford, proposed a modified holographicbound, which has since been found towork even in situations where the boundswe discussed earlier cannot be applied.Bousso’s formulation starts with any suit-able 2-D surface; it may be closed like asphere or open like a sheet of paper. Onethen imagines a brief burst of light issuingsimultaneously and perpendicularly fromall over one side of the surface. The onlydemand is that the imaginary light raysare converging to start with. Light emit-ted from the inner surface of a sphericalshell, for instance, satisfies that require-ment. One then considers the entropy ofthe matter and radiation that these imag-inary rays traverse, up to the points wherethey start crossing. Bousso conjecturedthat this entropy cannot exceed the en-tropy represented by the initial surface—

one quarter of its area, measured inPlanck areas. This is a different way of tal-lying up the entropy than that used in theoriginal holographic bound. Bousso’sbound refers not to the entropy of a re-gion at one time but rather to the sum ofentropies of locales at a variety of times:those that are “illuminated” by the lightburst from the surface.

Bousso’s bound subsumes other en-tropy bounds while avoiding their limi-tations. Both the universal entropybound and the ’t Hooft-Susskind form ofthe holographic bound can be deducedfrom Bousso’s for any isolated systemthat is not evolving rapidly and whosegravitational field is not strong. Whenthese conditions are overstepped—as fora collapsing sphere of matter already in-side a black hole—these bounds eventu-

ally fail, whereas Bousso’s bound con-tinues to hold. Bousso has also shownthat his strategy can be used to locate the2-D surfaces on which holograms of theworld can be set up.

Augurs of a RevolutionRESEARCHERS HAVE proposed manyother entropy bounds. The proliferationof variations on the holographic motifmakes it clear that the subject has not yetreached the status of physical law. Butalthough the holographic way of think-ing is not yet fully understood, it seemsto be here to stay. And with it comes arealization that the fundamental belief,prevalent for 50 years, that field theoryis the ultimate language of physics mustgive way. Fields, such as the electromag-netic field, vary continuously from pointto point, and they thereby describe an in-finity of degrees of freedom. Superstring

theory also embraces an infinite numberof degrees of freedom. Holography re-stricts the number of degrees of freedomthat can be present inside a boundingsurface to a finite number; field theorywith its infinity cannot be the final story.Furthermore, even if the infinity is tamed,the mysterious dependence of informa-tion on surface area must be somehowaccommodated.

Holography may be a guide to a bettertheory. What is the fundamental theorylike? The chain of reasoning involvingholography suggests to some, notably LeeSmolin of the Perimeter Institute for The-oretical Physics in Waterloo, that such a fi-nal theory must be concerned not withfields, not even with spacetime, but ratherwith information exchange among physi-cal processes. If so, the vision of informa-tion as the stuff the world is made of willhave found a worthy embodiment.


Black Hole Thermodynamics. Jacob D. Bekenstein in Physics Today, Vol. 33, No. 1, pages 24–31; January 1980.

Black Holes and Time Warps: Einstein’s Outrageous Legacy. Kip S. Thorne. W. W. Norton, 1995.

Black Holes and the Information Paradox. Leonard Susskind in Scientific American, Vol. 276, No. 4, pages 52–57; April 1997.

The Universe in a Nutshell. Stephen Hawking. Bantam Books, 2001.

Three Roads to Quantum Gravity. Lee Smolin. Basic Books, 2002.


OUR INNATE PERCEPTIONthat the world is three-dimensional could be anextraordinary illusion.



IMAG

ING

BY

TRU

CO

LLAG

E

The temple of Apollo, cradled in the spec-tacular mountainscape at Delphi, was the most important reli-gious site of the ancient Greek world, for it housed the power-ful oracle. Generals sought the oracle’s advice on strategy.Colonists asked for guidance before they set sail for Italy, Spainand Africa. Private citizens inquired about health problems andinvestments. The oracle’s advice figures prominently in themyths. When Orestes asked whether he should seek vengeanceon his mother for murdering his father, the oracle encouragedhim. Oedipus, warned by the oracle that he would murder hisfather and marry his mother, strove, with famous lack of suc-cess, to avoid his fate.

The oracle of Delphi functioned in a specific place, the ady-ton, or “no entry” area of the temple’s core, and through a spe-cific person, the Pythia, who was chosen to speak, as a pos-sessed medium, for Apollo, the god of prophecy. Extraordi-narily for misogynist Greece, the Pythia was a woman. Andunlike most Greek priests and priestesses, the Pythia did notinherit her office through noble family connections. Althoughthe Pythia had to be from Delphi, she could be old or young,rich or poor, well educated or illiterate. She went through along and intense period of conditioning, supported by a sis-terhood of Delphic women who tended the eternal sacred firein the temple.


Questioning

When science meets religion at this

ancient Greek site, the two turn out

to be on better terms than scholars

had originally thought

Delphicthe

Oracle

By John R. Hale, Jelle Zeilinga de Boer, Jeffrey P. Chanton and Henry A. SpillerOPENING PHOTOGRAPH BY SANJAY KOTHARI

DELPHIC ORACLE is shown inhaling vapors in thisphotographic interpretation, because new evidencesupports ancient assertions that intoxicating gaseswere a source of her inspiration. In reality, thegases would have been invisible.


The Classical ExplanationTRADITION ATTRIBUTED the prophetic inspi-ration of the powerful oracle to geologic phe-nomena: a chasm in the earth, a vapor thatrose from it, and a spring. Roughly a centu-ry ago scholars rejected this explanationwhen archaeologists digging at the sitecould find no chasm and detect no gases.The ancient testimony, however, is wide-spread, and it comes from a variety ofsources: historians such as Pliny andDiodorus, philosophers such as Plato,the poets Aeschylus and Cicero, the ge-ographer Strabo, the travel writer Pau-sanias, and even a priest of Apollo whoserved at Delphi, the famous essayist andbiographer Plutarch.

Strabo (64 B.C.–A.D. 25) wrote: “Theysay that the seat of the oracle is a cavern hol-lowed deep down in the earth, with a rathernarrow mouth, from which rises a pneuma[gas, vapor, breath; hence our words “pneumat-ic” and “pneumonia”] that produces divine posses-sion. A tripod is set above this cleft, mounting which,the Pythia inhales the vapor and prophesies.”

Plutarch (A.D. 46–120) left an extended eyewitness accountof the workings of the oracle. He described the relationshipsamong god, woman and gas by likening Apollo to a musician,the woman to his instrument and the pneuma to the plectrumwith which he touched her to make her speak. But Plutarch em-phasized that the pneuma was only a trigger. It was really thepreconditioning and purification (certainly including sexual ab-stinence, possibly including fasting) of the chosen woman thatmade her capable of responding to exposure to the pneuma. Anordinary person could detect the smell of the gas without pass-ing into an oracular trance.

Plutarch also recorded a number of physical characteristicsabout the pneuma. It smelled like sweet perfume. It was emit-ted “as if from a spring” in the adyton where the Pythia sat, but

priests and consultants could on some occasions smell it in theantechamber where they waited for her responses. It could riseeither as a free gas or in water. In Plutarch’s day the emissionhad become weak and irregular, the cause, in his opinion, ofthe weakening influence of the Delphic oracle in world affairs.He suggested that either the vital essence had run out or thatheavy rains had diluted it or a great earthquake more than fourcenturies earlier had partially blocked its vent. Maybe, he con-tinued, the vapor had found a new outlet. Plutarch’s theoriesabout the lessening of the emission make it clear that he be-lieved it originated in the rock below the temple.

A traveler in the next generation, Pausanias, echoes Plutarch’smention of the pneuma rising in water. Pausanias wrote that hesaw on the slope above the temple a spring called Kassotis, whichhe had heard plunged underground and then emerged again inthe adyton, where its waters made the women prophetic.

Plutarch and other sources indicate that during normal ses-sions the woman who served as Pythia was in a mild trance. Shewas able to sit upright on the tripod and might spend a con-siderable amount of time there (although when the line of con-sultants was long, a second and even a third Pythia might have


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■ For the past century, scholars have discounted as myththe traditional explanation that vapors rising out of theearth intoxicated, and inspired, the prophesyingpriestesses at Delphi.

■ Recent scientific findings show that this description was,in fact, extraordinarily accurate.

■ In particular, the authors have identified two geologicfaults that intersect precisely under the site of the oracle.

■ Furthermore, the petrochemical-rich layers in thelimestone formations of the region most likely producedethylene, a gas that induces a trancelike state and thatcould have risen through fissures created by the faults.

Overview/An Intoxicating Tale

ONLY SURVIVING DEPICTION of the priestess, or Pythia, at Delphi from thetime the oracle was active reveals the low-ceilinged chamber and thePythia seated on a tripod. In one hand she holds a sprig of laurel (Apollo’ssacred tree); in the other, a cup, presumably containing water from a springthat bubbled up into the chamber, bringing with it gases that induced atrance. This mythological scene shows King Aegeus of Athens questioningthe first Pythia, Themis. An Athenian potter made the cup in about 440 B.C.


to relieve her). She could hear the questions and gave intelligi-ble answers. During the oracular sessions, the Pythia spoke inan altered voice and tended to chant her responses, indulgingin wordplay and puns. Afterward, according to Plutarch, shewas like a runner after a race or a dancer after an ecstatic dance.

On one occasion, which either Plutarch himself or one ofhis colleagues witnessed, temple authorities forced the Pythiato prophesy on an inauspicious day to please the members ofan important embassy. She went down to the subterranean ady-ton unwillingly and at once was seized by a powerful and ma-lignant spirit. In this state of possession, instead of speaking orchanting as she normally did, the Pythia groaned and shrieked,threw herself about violently and eventually rushed at thedoors, where she collapsed. The frightened consultants andpriests at first ran away, but they later came back and pickedher up. She died after a few days.

The New TraditionGENERATIONS OF SCHOLARS accepted these accounts.Then, in about 1900, a young English classicist named AdolphePaul Oppé visited excavations being carried out by French ar-chaeologists at Delphi. He failed to see any chasm or to hear re-ports of any gases, and he published an influential article inwhich he made three critical claims. First, no chasm or gaseousemission had ever existed in the temple at Delphi. Second, evenif it had, no natural gas could produce a state resembling spir-itual possession. Third, Plutarch’s account of a Pythia who hada violent frenzy and died shortly afterward was inconsistent

with the customary description of a Pythia sitting on the tripodand chanting her prophecies. Oppé concluded that all the an-cient testimony could be explained away.

Oppé’s debunking took the academic world by storm. Hisopinions were so strongly expressed that his theory became thenew orthodoxy. The absence of the wide opening that theFrench archaeologists had expected seemed to prove his argu-ment. Additional support for Oppé’s theory came in 1950,when French archaeologist Pierre Amandry added the furthernegative that only a volcanic area, which Delphi was not, couldhave produced a gas such as the one described in the classicalsources. The case seemed closed. The original tradition of theGreek and Latin authors lived on only in popular books andin the words of local guides, which, in Oppé’s opinion, hadbeen the source of the chasm and vapor myth in the first place.

The situation changed in the 1980s, when a United NationsDevelopment Project undertook a survey in Greece of activefaults (those along which earthquakes have been generated inthe past few hundred years). As a member of that survey, oneof us (de Boer, who is a geologist) noted exposed fault facesboth east and west of the sanctuary. He interpreted them asmarking the line of a fault that ran along the south slope ofMount Parnassus and under the site of the oracle. But beingaware of the classical tradition and unaware of the modernskepticism and debunking, he attributed no special importanceto his observation.

More than a decade later de Boer met another of us (Hale)at an archaeological site in Portugal where Hale, who is an ar-chaeologist, sought de Boer’s geological opinion on the evi-dence for earthquake damage at an ancient Roman villa. Overa bottle of wine, de Boer mentioned that he had seen the faultthat ran under the temple at Delphi. Hale, who had learned theapproved view as an undergraduate, contradicted him. But inthe lively conversation that ensued, de Boer converted him withhis description of the fault, his account of how faults couldbring gases to the surface and his references to the classical au-thors. Realizing the importance of the observation for the in-terpretation of the ancient accounts, the two decided to forma team for further exploration of the site.

The Classical Explanation RevisitedDURING OUR FIRST F IELD TRIP , in 1996, the two of usconducted geological surveys and examined the temple foun-


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Extraordinarily for misogynistGreece, the Pythia was a woman. And she did not inherit her office

through noble family connections.

EXPERIMENTS with anesthesiaconducted by Isabella Herb(standing) in the mid-20thcentury turned out to becrucial in solving the mysteryof what gas might have beenemitted beneath the temple atDelphi. Herb and hercolleagues had discoveredthat low concentrations ofethylene could produce atrancelike state.


dations that the French archaeologists had exposed. The tem-ple has a number of anomalous features that would call forsome special interpretation of its function even if the reportsof Plutarch and others had not been preserved. First, the innersanctum is sunken, lying two to four meters below the level ofthe surrounding floor. Second, it is asymmetrical: a break in theinternal colonnade accommodates some now vanished struc-ture or feature. Third, built directly into the foundations nextto the recessed area is an elaborate drain for spring water, alongwith other subterranean passages. Thus, the temple of Apolloseemed designed to enclose a particular piece of terrain that in-cluded a water source, rather than to provide a house for theimage of the god, the normal function of a temple building.

During that first exploration, we traced the major east-westfault line, called the Delphi fault, that de Boer had observedduring the earlier survey. Later we were to discover the ex-posed face of a second fault in a ravine above the temple. Thissecond line, which we named the Kerna fault, ran northwest-southeast and cut across the Delphi fault at the oracle site. Aline of springs that ran through the sanctuary and intersectedthe temple marked the location of the Kerna fault below the

ancient terracing and the accumulated debris from rockslides.That same year a father-and-son archaeological and geo-

logical team, Michael D. Higgins and Reynold Higgins, pub-lished a book that suggested we were on the right track. In theirGeological Companion to Greece and the Aegean, they notedthat the line of springs did indeed suggest the presence of a“steep fault” running northwest-southeast through the sanc-tuary. They also pointed out that no geological reason necessi-tates rejecting the ancient tradition.

Higgins and Higgins theorized that the gas emitted mighthave been carbon dioxide. A decade earlier a different scientif-ic team had detected such an emission at another temple ofApollo, the one at Hierapolis (modern Pamukkale) in Asia Mi-nor (now Turkey, and home to the ruins of many great Greekcities). Following the lead of Strabo, modern researchers havediscovered that the Apollo temple at Hierapolis had been de-liberately sited over a vent of toxic gases, which in the finishedtemple emerged from a grotto in the building’s foundations.

The temple at Hierapolis was not a place of prophecy, andthe carbon dioxide was not so much intoxicating as toxic,claiming the lives of sacrificial animals, from sparrows to bulls.


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TWO GEOLOGIC FAULTS intersect under the Temple of Apollo at Delphi (aboveand details on opposite page). This intersection made the rock more permeable and provided pathways (visible in cutaway) along which bothgroundwater and gases were able to rise. Tectonic activity heated the

limestone adjacent to the faults to temperatures high enough to vaporizesome of its petrochemical constituents. These gaseous vapors then movedthrough the fissures created by the faults into the small, enclosed chamberlying below the floor level of the temple, where the oracle sat to prophesy.

KERNAFAULT

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Even today the gas, which is emitted irregularly, kills sparrowsthat perch on the wire fence intended to keep people out. Oth-er temples of Apollo in Turkey, however, were oracular, andthey were built over active springs, such as those at Didyma andClaros. A link clearly seemed to be emerging between templesof Apollo and sites of geologic activity.

The Perfect GasALTHOUGH THE NEWLY DISCOVERED faults at Delphiindicated that gases and spring water could have reached thesurface through cracks that the faults created in the ground be-low the temple, they did not explain the generation of the gas-es themselves. De Boer, however, had observed travertine de-posits, flows of calcite laid down by spring water, coating theslopes above the temple and even an ancient retaining wall.These flows suggested to him that the water had risen through

deep layers of limestone to the surface, where it had deposit-ed calcite mineralizations (a phenomenon also seen at Hier-apolis in Turkey). A search through Greek geologic studies ofMount Parnassus revealed that among the Cretaceous rockformations in the vicinity of the temple were layers of bitumi-nous limestone that had a petrochemical content as high as 20percent.

De Boer now began to see a system taking shape. Faults,which were well exposed on the uplifted slopes of Mount Par-nassus, had cut through bituminous limestone. Movementalong the faults created friction that heated the limestone to apoint at which the petrochemicals vaporized. They then rosealong the fault with the spring water, especially at points wherethe presence of cross-faulting made the rock more permeable.Over time, gas emissions would decrease as calcitic crustsclogged the spaces inside the fault, only to be restored with thenext tectonic slip.

De Boer’s reasoning seemed in accord with the findings ofthe early 20th-century French archaeologists, who had finallyreached bedrock under the adyton a few years after the publi-cation of Oppé’s article. Beneath a stratum of brown clay, theyencountered rock that was “fissured by the action of the wa-ters.” We believe that faulting and fracturing rather than wa-ter may have created these fissures, although groundwater mayhave widened them over time; in early attempts to reach bed-rock, the French archaeologists noted that the holes kept fillingup with water. We also believe that the visible chasm in the ady-ton may have been a gaping fissure that extended into the lay-er of clay above the faulted bedrock.

As careful geologic research and reasoning solved riddle af-


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JOHN HALE, JELLE DE BOER, JEFF CHANTON and RICK SPILLERhave formed an interdisciplinary team to investigate the Delphicoracle. Hale, an archaeologist at the University of Louisville, haswritten two previous articles for Scientific American. De Boer is aprofessor of geology at Wesleyan University. Chanton, a chemist,teaches in the department of oceanography at Florida State Uni-versity, and toxicologist Spiller is director of the Kentucky Region-al Poison Center.

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TEMPLE OF APOLLO is viewed (at left) along the line of the Delphi fault. The location of the oracle was near the block set inside the sunken areawithin the temple’s foundations. In the photograph above, one of theauthors (de Boer) sits on the block, in much the same spot where thePythia would have sat on her tripod centuries ago.


ter riddle, we were still left with the question of what gasesmight have emerged. De Boer learned that geologists workingin the Gulf of Mexico had analyzed gases that bubbled up alongsubmerged faults. They had found that active faults in this areaof bituminous limestone were producing light hydrocarbon gas-es such as methane and ethane. Could the same have been trueat Delphi?

To find out, we asked for permission to take samples ofspring water from Delphi, along with samples of the travertinerock laid down by ancient springs. We hoped to discover in thisporous rock traces of the gases that were brought to the surfacein earlier times. At this point, Chanton, who is a chemist, joinedthe team. In the travertine samples collected by de Boer andHale, he found methane and ethane, the latter a decompositionproduct of ethylene. Chanton then visited Greece to collect wa-ter samples from springs in and around the oracle site. Analy-sis of the water from the Kerna spring in the sanctuary itselfrevealed the presence of methane, ethane and ethylene. Becauseethylene has a sweet odor, the presence of this gas seemed tolend support to Plutarch’s description of a gas that smelled likeexpensive perfume.

To help interpret the possible effects of such gases on hu-man subjects in a confined space, one like the adyton, Spiller,a toxicologist, became a member of the project. His work with“huffers”—teenage drug users who get high on the fumes fromsubstances such as glue and paint thinner, most of which con-tain light hydrocarbon gases—had shown a number of paral-lels with the behavior reported for the trance state of the Pythia.

Spiller uncovered even more parallels in the reports of ex-periments on the anesthetic properties of ethylene carried outmore than half a century ago by pioneering American anesthe-siologist Isabella Herb. She had found that a 20 percent mix-ture of ethylene produced unconsciousness but that lower con-centrations induced a trance state. In most cases, the trance wasbenign: the patient remained conscious, was able to sit up andto respond to questions, experienced out-of-body feelings andeuphoria, and had amnesia after being taken off the gas. Butoccasionally Herb would see violent reactions, the patient ut-tering wild, incoherent cries and thrashing about. Had a patientvomited during such a frenzy and ingested some of the vomitinto the lungs, pneumonia and death would inevitably have fol-lowed. Thus, according to Spiller’s analysis, inhaling ethylenecould account for all the various descriptions of the pneuma

at Delphi—its sweet odor and its variable effects on human sub-jects, including even the potential for death.

An Unexpected InspirationTWO THOUSAND YEARS AGO Plutarch was interested inreconciling religion and science. As priest of Apollo, he had torespond to religious conservatives who objected to the notionthat a god might use a fluctuating natural gas to perform a mir-acle. Why not enter the woman’s body directly? Plutarch be-lieved that the gods had to rely on the materials of this corruptand transitory world to accomplish their works. God thoughhe was, Apollo had to speak his prophecies through the voicesof mortals, and he had to inspire them with stimuli that werepart of the natural world. Plutarch’s careful observations andreporting of data about the gaseous emissions at Delphi showthat the ancients did not try to exclude scientific inquiry fromreligious understanding.

The primary lesson we took away from our Delphic oracleproject is not the well-worn message that modern science canelucidate ancient curiosities. Perhaps more important is howmuch we have to gain if we approach problems with the samebroad-minded and interdisciplinary attitude that the Greeksthemselves displayed.


The Delphic Oracle. H. W. Parke and D.E.W. Wormell. Basil Blackwell, 1956.

Plutarch’s Moralia. Vol. 5. Loeb Classical Library. 6th printing. Harvard University Press, 1992.

A Geological Companion to Greece and the Aegean. Michael DenisHiggins and Reynold Higgins. Cornell University Press, 1996.

New Evidence for the Geological Origins of the Ancient Delphic Oracle(Greece). J. Z. de Boer, J. R. Hale and J. Chanton in Geology, Vol. 29, No. 8,pages 707–711; 2001.

The Delphic Oracle: A Multidisciplinary Defense of the Gaseous VentTheory. Henry A. Spiller, John R. Hale, Jelle Z. de Boer in Journal of ClinicalToxicology, Vol. 40, No. 2, pages 189–196; 2002.


A link clearly seemed to be emerging

between temples of Apollo and sites of geologic activity.

A segment based on thisarticle will air July 24 onNational Geographic Today, a program on the NationalGeographic Channel. Pleasecheck your local listings.


A DIVERSITY OF APES ranged across the Old Worldduring the Miocene epoch, between 22 million and 5.5million years ago. Proconsul lived in East Africa,Oreopithecus in Italy, Sivapithecus in South Asia, andOuranopithecus and Dryopithecus—members of thelineage thought to have given rise to African apes andhumans—in Greece and western and central Europe,respectively. These renderings were created through aprocess akin to that practiced by forensic illustrators.To learn more about how artist John Gurche drew fleshfrom stone, check out www.sciam.com/onthewebSivapithecus

Proconsul


Dryopithecus

Planetof the



“It is therefore probable that Africa was for-merly inhabited by extinct apes closely alliedto the gorilla and chimpanzee; as these twospecies are now man’s closest allies, it is

somewhat more probable that our early progenitorslived on the African continent than elsewhere.”

So mused Charles Darwin in his 1871 work, TheDescent of Man. Although no African fossil apes or hu-mans were known at the time, remains recovered sincethen have largely confirmed his sage prediction abouthuman origins. There is, however, considerably morecomplexity to the story than even Darwin could haveimagined. Current fossil and genetic analyses indicatethat the last common ancestor of humans and our clos-est living relative, the chimpanzee, surely arose inAfrica, around six million to eight million years ago. Butfrom where did this creature’s own forebears come? Pa-leoanthropologists have long presumed that they, too,

During theMiocene epoch,as many as 100species of apesroamedthroughout theOld World. Newfossils suggestthat the onesthat gave rise toliving great apesand humansevolved not in Africa butEurasia

By David R. Begun

Fossil ape reconstructionsby John Gurche

Oreopithecus

Ouranopithecus

Apes


had African roots. Mounting fossil evi-dence suggests that this received wisdomis flawed.

Today’s apes are few in number andin kind. But between 22 million and 5.5million years ago, a time known as theMiocene epoch, apes ruled the primateworld. Up to 100 ape species rangedthroughout the Old World, from Franceto China in Eurasia and from Kenya toNamibia in Africa. Out of this dazzlingdiversity, the comparatively limited num-ber of apes and humans arose. Yet fossilsof great apes—the large-bodied grouprepresented today by chimpanzees, goril-las and orangutans (gibbons and siamangsmake up the so-called lesser apes)—haveturned up only in western and central Eu-rope, Greece, Turkey, South Asia andChina. It is thus becoming clear that, byDarwin’s logic, Eurasia is more likelythan Africa to have been the birthplace ofthe family that encompasses great apesand humans, the hominids. (The term“hominid” has traditionally been re-served for humans and protohumans, butscientists are increasingly placing ourgreat ape kin in the definition as well andusing another word, “hominin,” to referto the human subset. The word “homi-noid” encompasses all apes—including

gibbons and siamangs—and humans.)Perhaps it should not come as a sur-

prise that the apes that gave rise to hom-inids may have evolved in Eurasia insteadof Africa: the combined effects of migra-tion, climate change, tectonic activity andecological shifts on a scale unsurpassedsince the Miocene made this region ahotbed of hominoid evolutionary exper-imentation. The result was a panoply ofapes, two lineages of which would even-tually find themselves well positioned tocolonize Southeast Asia and Africa andultimately to spawn modern great apesand humans.

Paleoanthropology has come a longway since Georges Cuvier, the Frenchnatural historian and founder of verte-brate paleontology, wrote in 1812 that“l’homme fossile n’existe pas” (“fossilman does not exist”). He included all fos-sil primates in his declaration. Althoughthat statement seems unreasonable to-day, evidence that primates lived along-side animals then known to be extinct—mastodons, giant ground sloths and prim-itive ungulates, or hoofed mammals, forexample—was quite poor. Ironically, Cu-vier himself described what scholarswould later identify as the first fossil pri-mate ever named, Adapis parisiensis Cu-

vier 1822, a lemur from the chalk minesof Paris that he mistook for an ungulate.It wasn’t until 1837, shortly after Cuvier’sdeath, that his disciple Édouard Lartet de-scribed the first fossil higher primate rec-ognized as such. Now known as Pliopith-ecus, this jaw from southeastern France,and other specimens like it, finally con-vinced scholars that such creatures hadonce inhabited the primeval forests of Eu-rope. Nearly 20 years later Lartet un-veiled the first fossil great ape, Dryopith-ecus, from the French Pyrénées.

In the remaining years of the 19th cen-tury and well into the 20th, paleontolo-gists recovered many more fragments ofape jaws and teeth, along with a few limbbones, in Spain, France, Germany, Aus-tria, Slovakia, Hungary, Georgia andTurkey. By the 1920s, however, attentionhad shifted from Europe to South Asia(India and Pakistan) and Africa (mainlyKenya), as a result of spectacular finds inthose regions, and the apes of Eurasiawere all but forgotten. But fossil discov-eries of the past two decades have rekin-dled intense interest in Eurasian fossilapes, in large part because paleontologistshave at last recovered specimens completeenough to address what these animalslooked like and how they are related toliving apes and humans.

The First ApesTO DATE, RESEARCHERS have iden-tified as many as 40 genera of Miocenefossil apes from localities across the OldWorld—eight times the number that sur-vive today. Such diversity seems to havecharacterized the ape family from the out-set: almost as soon as apes appear in thefossil record, there are lots of them. So far14 genera are known to have inhabitedAfrica during the early Miocene alone,between 22 million and 17 million yearsago. And considering the extremely im-


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■ Only five ape genera exist today, and they are restricted to a few pockets ofAfrica and Southeast Asia. Between 22 million and 5.5 million years ago, incontrast, dozens of ape genera lived throughout the Old World.

■ Scientists have long assumed that the ancestors of modern African apes andhumans evolved solely in Africa. But a growing body of evidence indicates thatalthough Africa spawned the first apes, Eurasia was the birthplace of the greatape and human clade.

■ The fossil record suggests that living great apes and humans are descendedfrom two ancient Eurasian ape lineages: one represented by Sivapithecus fromAsia (the probable forebear of the orangutan) and the other by Dryopithecusfrom Europe (the likely ancestor of African apes and humans).

Overview/Ape Revolution

17 to 16.5million years ago

16.5 to 13.5million years ago

13.5 to 8 million years ago1 32


perfect nature of the fossil record, chancesare that this figure significantly underrep-resents the number of apes that actuallyexisted at that time.

Like living apes, these creatures var-ied considerably in size. The smallestweighed in at a mere three kilograms,hardly more than a small housecat; thelargest tipped the scales at a gorillalikeheft of 80 kilograms. They were evenmore diverse than their modern counter-parts in terms of what they ate, withsome specializing in leaves and others infruits and nuts, although the majoritysubsisted on ripe fruits, as most apes dotoday. The biggest difference betweenthose first apes and extant ones lay intheir posture and means of gettingaround. Whereas modern apes exhibit arich repertoire of locomotory modes—

from the highly acrobatic brachiationemployed by the arboreal gibbon to thegorilla’s terrestrial knuckle walking—

early Miocene apes were obliged to travel along tree branches on all fours.

To understand why the first apes wererestricted in this way, consider the bodyplan of the early Miocene ape. The best-known ape from this period is Proconsul,exceptionally complete fossils of whichhave come from sites on Kenya’s RusingaIsland [see “The Hunt for Proconsul,” byAlan Walker and Mark Teaford; Scien-tific American, January 1989]. Special-ists currently recognize four species ofProconsul, which ranged in size fromabout 10 kilograms to possibly as muchas 80 kilograms. Proconsul gives us agood idea of the anatomy and locomo-

tion of an early ape. Like all extant apes,this one lacked a tail. And it had moremobile hips, shoulders, wrists, ankles,hands and feet than those of monkeys,presaging the fundamental adaptationsthat today’s apes and humans have forflexibility in these joints. In modern apes,this augmented mobility enables theirunique pattern of movement, swingingfrom branch to branch. In humans, thesecapabilities have been exapted, or bor-rowed, in an evolutionary sense, for en-hanced manipulation in the upper limb—

something that allowed our ancestors tostart making tools, among other things.

At the same time, however, Proconsul


DAVID R. BEGUN is professor of anthropology at the University of Toronto. He received his Ph.D.in physical anthropology from the University of Pennsylvania in 1987. Focusing on Miocenehominoid evolution, Begun has excavated and surveyed fossil localities in Spain, Hungary,Turkey and Kenya. He is currently working with colleagues in Turkey and Hungary on sev-eral fossil ape sites and is trying to reconstruct the landscapes and mammalian dispersalpatterns that characterized the Old World between 20 million and two million years ago.TH

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APES ON THE MOVE: Africa was the cradle of apekind, having spawned the first apes morethan 20 million years ago. But it was not long before these animals colonized the rest ofthe Old World. Changes in sea level alternately connected Africa to and isolated it fromEurasia and thus played a critical role in ape evolution. A land bridge joining East Africa toEurasia between 17 million and 16.5 million years ago enabled early Miocene apes toinvade Eurasia (1). Over the next few million years, they spread to western Europe andthe Far East, and great apes evolved; some primitive apes returned to Africa (2). Isolatedfrom Africa by elevated sea levels, the early Eurasian great apes radiated into a number offorms (3). Drastic climate changes at the end of the Late Miocene wiped out most of theEurasian great apes. The two lineages that survived—those represented by Sivapithecusand Dryopithecus—did so by moving into Southeast Asia and the African tropics (4).

9 to 6 million years ago

GriphopithecusGriphopithecus

Griphopithecus

GriphopithecusAnkarapithecusNew taxon

Heliopithecus

Sivapithecus

Gigantopithecus

Sivapithecus

Lufengpithecus

Proconsul AfropithecusKenyapithecus (among many others)

OuranopithecusOreopithecus

Dryopithecus

Dryopithecus

Dryopithecus

4

Other apes

MIOCENE APE FOSSIL LOCALITIES


and its cohorts retained a number ofprimitive, monkeylike characteristics inthe backbone, pelvis and forelimbs, leav-ing them, like their monkey forebears,better suited to traveling along the tops oftree branches than hanging and swingingfrom limb to limb. (Intriguingly, one enig-matic early Miocene genus from Uganda,Morotopithecus, may have been moresuspensory, but the evidence is inconclu-sive.) Only when early apes shed more ofthis evolutionary baggage could they be-gin to adopt the forms of locomotion fa-vored by contemporary apes.

Passage to EurasiaMOST OF THE EARLY Miocene apeswent extinct. But one of them—perhapsAfropithecus from Kenya—was ancestralto the species that first made its way overto Eurasia some 16.5 million years ago.At around that time global sea levelsdropped, exposing a land bridge betweenAfrica and Eurasia. A mammalian exodusensued. Among the creatures that mi-grated out of their African homelandwere elephants, rodents, ungulates suchas pigs and antelopes, a few exotic ani-mals such as aardvarks, and primates.

The apes that journeyed to Eurasiafrom Africa appear to have passed through

Saudi Arabia, where the remains of He-liopithecus, an ape similar to Afropithe-cus, have been found. Both Afropithecusand Heliopithecus (which some workersregard as members of the same genus)had a thick covering of enamel on theirteeth—good for processing hard foods,such as nuts, and tough foods protectedby durable husks. This dental innovationmay have played a key role in helpingtheir descendants establish a foothold inthe forests of Eurasia by enabling them toexploit food resources not available toProconsul and most earlier apes. By thetime the seas rose to swallow the bridgelinking Africa to Eurasia half a millionyears later, apes had ensconced them-selves in this new land.

The movement of organisms into newenvironments drives speciation, and thearrival of apes in Eurasia was no excep-tion. Indeed, within a geologic blink of aneye, these primates adapted to the novelecological conditions and diversified intoa plethora of forms—at least eight knownin just 1.5 million years. This flurry of evo-lutionary activity laid the groundwork forthe emergence of great apes and humans.But only recently have researchers begunto realize just how important Eurasia wasin this regard. Paleontologists traditional-

ly thought that apes more sophisticated intheir food-processing abilities than Afro-pithecus and Heliopithecus reached Eura-sia about 15 million years ago, around thetime they first appear in Africa. This fitwith the notion that they arose in Africaand then dispersed northward. New fossilevidence, however, indicates that ad-vanced apes (those with massive jaws andlarge, grinding teeth) were actually inEurasia far earlier than that. In 2001 and2003 my colleagues and I described amore modern-looking ape, Griphopithe-cus, from 16.5-million-year-old sites inGermany and Turkey, pushing theEurasian ape record back by more than amillion years.

The apparent absence of such newermodels in Africa between 17 million and15 million years ago suggests that, con-trary to the long-held view of this regionas the wellspring of all ape forms, somehominoids began evolving modern cra-nial and dental features in Eurasia and re-turned to Africa changed into more ad-vanced species only after the sea recededagain. (A few genera—such as Kenyapith-ecus from Fort Ternan, Kenya—may havegone on to develop some postcranialadaptations to life on the ground, but forthe most part, these animals still looked


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What Is an Ape, Anyway?LIVING APES—chimpanzees, gorillas, orangutans, gibbons andsiamangs—and humans share a constellation of traits that setthem apart from other primates. To start, they lack an externaltail, which is more important than it may sound because itmeans that the torso and limbs must meet certain requirementsof movement formerly executed by the tail. Apes and humansthus have highly flexible limbs, enabling them to lift their armsabove their heads and to suspend themselves by their arms.(This is why all apes have long and massive arms compared totheir legs; humans, for their part, modified their limbproportions as they became bipedal.) For the same reason, allapes have broad chests, short lower backs, mobile hips andankles, powerfully grasping feet and a more vertical posturethan most other primates have. In addition, apes are relativelybig, especially the great apes (chimps, gorillas andorangutans), which grow and reproduce much more slowly thanother simians do. Great apes and humans also possess thelargest brains in the primate realm and are more intelligent bynearly all measures—tool use, mirror self-recognition, socialcomplexity and foraging strategy, among them—than any othermammal.

Fossil apes, then, are those primates that more closely

resemble living apes than anything else. Not surprisingly, earlyforms have fewer of the defining ape characteristics than dolater models. The early Miocene ape Proconsul, for example, wastailless, as evidenced by the morphology of its sacrum, the baseof the backbone, to which a tail would attach if present. ButProconsul had not yet evolved the limb mobility or brain sizeassociated with modern apes. Researchers generally agree thatthe 19-million-year-old Proconsul is the earliest unambiguousape in the fossil record. The classification of a number of otherearly Miocene “apes”—including Limnopithecus, Rangwapithecus,Micropithecus, Kalepithecus and Nyanzapithecus—has provedtrickier, owing to a lack of diagnostic postcranial remains. Thesecreatures might instead be more primitive primates that livedbefore Old World monkeys and apes went their separateevolutionary ways. I consider them apes mainly because of theapelike traits in their jaws and teeth. —D.R.B.

MONKEY PROCONSUL GREAT APE


FRONT VIEW OF VERTEBRAFRONT VIEW OF VERTEBRA

POSTERIORLYPOSITIONED PROJECTIONPOSTERIORLY POSITIONED PROJECTIONLATERALLY ORIENTED PROJECTIONLATERALLY ORIENTED PROJECTION

CROSS SECTION OF TORSOCROSS SECTION OF TORSO

BODY VIEWED FROM BELOW

SHOULDER BLADE ON SIDESHOULDER BLADE ON SIDE

SHOULDER BLADE ON BACKSHOULDER BLADE ON BACK

DEEP RIBCAGEDEEP RIBCAGESHALLOW RIBCAGESHALLOW RIBCAGE

ELBOW JOINT CAN FULLY EXTEND ELBOW JOINT CAN FULLY EXTEND

ELBOW JOINT CANNOT FULLY EXTENDELBOW JOINT CANNOT FULLY EXTEND

RESTRICTED SHOULDER JOINT

LONGER, MORE FLEXIBLE SPINE

RESTRICTED HIP JOINT

LEGS ANDARMSSAME

LENGTH

SMALL HANDS LARGE HANDS

ARMSLONGERTHANLEGS

HIGHLY MOBILE SHOULDER JOINT

SHORTER, STIFFER SPINE

HIGHLY MOBILE HIP JOINT

GOING GREAT APE: Primitive ape body plan and greatape body plan are contrasted here. The earliest apesstill had rather monkeylike bodies, built for travelingatop tree limbs on all fours. They possessed a longlower back; projections on their vertebrae oriented forflexibility; a deep rib cage; elbow joints designed for

power and speed; shoulder and hip joints that kept thelimbs mostly under the body; and arms and legs ofsimilar length. Great apes, in contrast, are adapted tohanging and swinging from tree branches. Theirvertebrae are fewer in number and bear a configurationof projections designed to stiffen the spine to support

a more vertical posture. Great apes also have abroader, shallower rib cage; a flexible elbow joint thatpermits full extension of the arm for suspension; highlymobile shoulder and hip joints that allow a much widerrange of limb motion; large, powerful, grasping hands;and upper limbs that are longer than their lower limbs.

PRIMITIVE APE GREAT APE


like their early Miocene predecessors fromthe neck down.)

Rise of the Great ApesBY THE END of the middle Miocene,roughly 13 million years ago, we have ev-idence for great apes in Eurasia, notablyLartet’s fossil great ape, Dryopithecus, inEurope and Sivapithecus in Asia. Like liv-ing great apes, these animals had long,strongly built jaws that housed large in-cisors, bladelike (as opposed to tusklike)canines, and long molars and premolarswith relatively simple chewing surfaces—

a feeding apparatus well suited to a dietof soft, ripe fruits. They also possessedshortened snouts, reflecting the reducedimportance of olfaction in favor of vision.Histological studies of the teeth of Dry-opithecus and Sivapithecus suggest thatthese creatures grew fairly slowly, as liv-ing great apes do, and that they probablyhad life histories similar to those of thegreat apes—maturing at a leisurely rate,living long lives, bearing one large off-spring at a time, and so forth. Other evi-dence hints that were they around today,

these early great apes might have evenmatched wits with modern ones: fossilbraincases of Dryopithecus indicate thatit was as large-brained as a chimpanzee ofcomparable proportions. We lack directclues to brain size in Sivapithecus, but giv-en that life history correlates stronglywith brain size, it is likely that this apewas similarly brainy.

Examinations of the limb skeletons ofthese two apes have revealed additionalgreat ape–like characteristics. Most im-portant, both Dryopithecus and Sivapith-ecus display adaptations to suspensory lo-comotion, especially in the elbow joint,which was fully extendable and stablethroughout the full range of motion.Among primates, this morphology isunique to apes, and it figures prominent-ly in their ability to hang and swing belowbranches. It also gives humans the abilityto throw with great speed and accuracy.For its part, Dryopithecus exhibits nu-merous other adaptations to suspension,both in the limb bones and in the handsand feet, which had powerful grasping ca-pabilities. Together these features strong-

ly suggest that Dryopithecus negotiatedthe forest canopy in much the way that liv-ing great apes do. Exactly how Sivapithe-cus got around is less clear. Some charac-teristics of this animal’s limbs are indica-tive of suspension, whereas others implythat it had more quadrupedal habits. In alllikelihood, Sivapithecus employed a modeof locomotion for which no modern ana-logue exists—the product of its ownunique ecological circumstances.

The Sivapithecus lineage thrived inAsia, producing offshoots in Turkey, Pak-istan, India, Nepal, China and SoutheastAsia. Most phylogenetic analyses concurthat it is from Sivapithecus that the livingorangutan, Pongo pygmaeus, is descend-ed. Today this ape, which dwells in therain forests of Borneo and Sumatra, is thesole survivor of that successful group.

In the west the radiation of great apeswas similarly grand. From the earliestspecies of Dryopithecus, D. fontani, theone found by Lartet, several other speciesemerged over about three million years.More specialized descendants of this lin-eage followed suit. Within two million


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FAMILY TREE of hominoids encompasses the lesser apes (siamangsand gibbons), great apes (orangutans, gorillas and chimpanzees), and humans.

Most Miocene apes were evolutionary dead ends. But researchers have identified a handful ofthem as candidate ancestors of living apes and humans. Proconsul, a primitive Miocene ape, isthought to have been the last common ancestor of the living hominoids; Sivapithecus, an early

great ape, is widely regarded as an orangutan forebear; and either Dryopithecus orOuranopithecus may have given rise to African apes and humans.

CATARRHINI

HYLOBATIDSCERCOPITHECOIDS

PLATYRRHINI

SPIDER MONKEY MACAQUE SIAMANG GIBBON ORANGUTAN GORILLA HUMAN CHIMPANZEE

HOMINIDSHOMINOIDS

SIVAPITHECUSPROCONSUL

OURANOPITHECUS

40 MILLION YEARS AGO

9 MYA

14 MYA

16 MYA19 MYA

25 MYA

6 MYADRYOPITHECUS


years four new species of Dryopithecuswould evolve and span the region fromnorthwestern Spain to the Republic ofGeorgia. But where Dryopithecus be-longs on the hominoid family tree hasproved controversial. Some studies linkDryopithecus to Asian apes; others po-sition it as the ancestor of all living greatapes. My own phylogenetic analysis ofthese animals—the most comprehensivein terms of the number of morphologicalcharacteristics considered—indicates thatDryopithecus is most closely related toan ape known as Ouranopithecus fromGreece and that one of these two Euro-pean genera was the likely ancestor ofAfrican apes and humans.

A Dryopithecus skull from Ruda-bánya, Hungary, that my colleagues andI discovered in 1999 bolsters that argu-ment. Nicknamed “Gabi” after its dis-coverer, Hungarian geologist GaborHernyák, it is the first specimen to pre-serve a key piece of anatomy: the connec-tion between the face and the braincase.Gabi shows that the cranium of Dryo-pithecus, like that of African apes and ear-ly fossil humans, had a long and lowbraincase, a flatter nasal region and an en-larged lower face. Perhaps most signifi-cant, it reveals that also like African apesand early humans, Dryopithecus was kli-

norhynch, meaning that viewed in profileits face tilts downward. Orangutans, incontrast—as well as Proconsul, gibbonsand siamangs—have faces that tilt up-ward, a condition known as airorhinchy.That fundamental aspect of Dryopithe-cus’s cranial architecture speaks stronglyto a close evolutionary relationship be-tween this animal and the African apesand humans lineage. Additional supportfor that link comes from the observationthat the Dryopithecus skull resemblesthat of an infant or juvenile chimpanzee—

a common feature of ancestral morphol-ogy. It follows, then, that the unique as-pects of adult cranial form in chim-panzees, gorillas and fossil humansevolved as modifications to the groundplan represented by Dryopithecus and liv-ing African ape youngsters.

One more Miocene ape deserves spe-cial mention. The best-known Eurasianfossil ape, in terms of the percentage ofthe skeleton recovered, is seven-million-year-old Oreopithecus from Italy. Firstdescribed in 1872 by renowned Frenchpaleontologist Paul Gervais, Oreopithe-cus was more specialized for dining onleaves than was any other Old World fos-sil monkey or ape. It survived very lateinto the Miocene in the dense and isolat-ed forests of the islands of Tuscany, which

would eventually be joined to one anoth-er and the rest of Europe by the retreat ofthe sea to form the backbone of the Ital-ian peninsula. Large-bodied and small-brained, this creature is so unusual look-ing that it is not clear whether it is a prim-itive form that predates the divergence ofgibbons and great apes or an early greatape or a close relative of Dryopithecus.Meike Köhler and Salvador Moyà-Solà ofthe Miquel Crusafont Institute of Paleon-tology in Barcelona have proposed thatOreopithecus walked bipedally along treelimbs and had a humanlike hand capableof a precision grip. Most paleoanthro-pologists, however, believe that it was in-stead a highly suspensory animal. What-ever Oreopithecus turns out to be, it is astriking reminder of how very diverse andsuccessful at adapting to new surround-ings the Eurasian apes were.

So what happened to the myriad spe-cies that did not evolve into the livinggreat apes and humans, and why did theancestors of extant species persevere?Clues have come from paleoclimatolog-ical studies. Throughout the middle Mio-cene, the great apes flourished in Eurasia,thanks to its then lush subtropical forestcover and consistently warm tempera-tures. These conditions assured a nearlycontinuous supply of ripe fruits and an


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Bigfoot BallyhooA FEW INDIVIDUALS, including someserious researchers, have argued thatthe Sivapithecus lineage of great apesfrom which the orangutan arose hasanother living descendant. Details ofthe beast’s anatomy vary from accountto account, but it is consistentlydescribed as a large, hirsute,nonhuman primate that walks uprightand has reportedly been spotted inlocales across North America and Asia.Unfortunately, this creature has morenames than evidence to support itsexistence (bigfoot, yeti, sasquatch,nyalmo, rimi, raksi-bombo, theabominable snowman—the list goes on).

Those who believe in bigfoot (on the basis of suspicioushairs, feces, footprints and fuzzy videotape) usually point tothe fossil great ape Gigantopithecus as its direct ancestor.Gigantopithecus was probably two to three times as large as a

gorilla and is known to have liveduntil about 300,000 years ago inChina and Southeast Asia.

There is no reason that such abeast could not persist today.After all, we know from the sub-fossil record that gorilla-sizelemurs lived on the island ofMadagascar until they weredriven to extinction by humansonly 1,000 years ago. Theproblem is that whereas we havefossils of 20-million-year-oldapes the size of very small cats,we do not have even a single bone

of this putative half-ton, bipedal great ape living in, among otherplaces, the continental U.S. Although every primatologist andprimate paleontologist I know would love for bigfoot to be real,the complete absence of hard evidence for its existence makesthat highly unlikely. —D.R.B.

ALLEGED bigfoot footprint, photographed near Coos Bay, Ore., in 1976.


easily traversed arboreal habitat with sev-eral tree stories. Climate changes in thelate Miocene brought an end to this easyliving. The combined effects of Alpine,Himalayan and East African mountainbuilding, shifting ocean currents, and theearly stages of polar ice cap formationprecipitated the birth of the modern Asianmonsoon cycle, the desiccation of EastAfrica and the development of a temper-ate climate in Europe. Most of the Eur-asian great apes went extinct as a result ofthis environmental overhaul. The two lin-eages that did persevere—those repre-sented by Sivapithecus and Dryopithe-cus—did so by moving south of the Trop-ic of Cancer, into Southeast Asia fromChina and into the African tropics fromEurope, both groups tracking the ecolog-ical settings to which they had adapted inEurasia.

The biogeographical model outlinedabove provides an important perspective

on a long-standing question in paleoan-thropology concerning how and why hu-mans came to walk on two legs. To ad-dress that issue, we need to know fromwhat form of locomotion bipedalismevolved. Lacking unambiguous fossil ev-idence of the earliest biped and its ances-tor, we cannot say with certainty whatthat ancestral condition was, but re-searchers generally fall into one of twotheoretical camps: those who think two-legged walking arose from arborealclimbing and suspension and those whothink it grew out of a terrestrial form oflocomotion, perhaps knuckle walking.

Your Great, Great Grand ApeTHE EURASIAN FOREBEAR of Africanapes and humans moved south in re-sponse to a drying and cooling of its en-virons that led to the replacement offorests with woodlands and grasslands. Ibelieve that adaptations to life on the

ground—knuckle walking in particular—

were critical in enabling this lineage towithstand that loss of arboreal habitatand make it to Africa. Once there, someapes returned to the forests, others settledinto varied woodland environments, andone ape—the one from which humans de-scended—eventually invaded open terri-tory by committing to life on the ground.

Flexibility in adaptation is the consis-tent message in ape and human evolution.Early Miocene apes left Africa because ofa new adaptation in their jaws and teeththat allowed them to exploit a diversity ofecological settings. Eurasian great apesevolved an array of skeletal adaptationsthat permitted them to live in varied envi-ronments as well as large brains to grap-ple with complex social and ecologicalchallenges. These modifications made itpossible for a few of them to survive thedramatic climate changes that took placeat the end of the Miocene and return to


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Lucky StrikesFOSSIL FINDS often result from a combinationof dumb luck and informed guessing. Suchwas the case with the discoveries of two of themost complete fossil great ape specimens onrecord. The first of these occurred at a siteknown as Can Llobateres in the VallèsPenedès region of Spain. Can Llobateres hadbeen yielding fragments of jaws and teethsince the 1940s, and in the late 1980s I wasinvited by local researchers to renewexcavations there. The first year I discoveredlittle other than how much sunburn andgazpacho I could stand. Undaunted, I returnedfor a second season, accompanied by my thenseven-year-old son, André. During a planningsession the day before the work was to begin,André made it clear that, after enduring manyhours in a stifling building without air-conditioning, he had had enough, so I took himto see the site. We went to the spots my teamhad excavated the year before and thenwandered up the hillside to other exposuresthat had looked intriguing but that we haddecided not to investigate at that time. Afterpoking around up there with André over thecourse of our impromptu visit, I resolved toconvince my collaborators to dig a test pit inthat area at some point during the season.

The next day we returned to the spot sothat I could show a colleague the sedimentsof interest, and as we worked to clear offsome of the overlying dirt, a great apepremolar popped out. We watched inamazement as the tooth rolled down the hill,seemingly in slow motion, and landed at ourfeet. A few days later we had recovered thefirst nearly whole face of Dryopithecus (top)and the most complete great ape from CanLlobateres in the 50-year history ofexcavations at the site. We subsequently

traced the same sedimentological layeracross the site and found some limbfragments in another area, which, whenexcavated more completely in the followingyear, produced the most complete skeletonof Dryopithecus known to this day.

Nine years later in Hungary my Hungariancolleagues and I were starting a new fieldseason at a locality called Rudabánya.Historically, Rudabánya had yieldednumerous Dryopithecus fossils, mostly teethand skeletal remains. Intensive excavationover the previous two years, however, failedto turn up any material. For the 1999 season Ithought we should concentrate our efforts on

STELLAR SPECIMENS of Dryopithecus, one of theearliest great apes, have come from sites in Spain(left) and Hungary (right).


Africa, around nine million years ago.Thus, the lineage that produced Africanapes and humans was preadapted to cop-ing with the problems of a radicallychanging environment. It is therefore notsurprising that one of these species even-tually evolved very large brains and so-phisticated forms of technology.

As an undergraduate more than 20years ago, I began to look at fossil apesout of the conviction that to understandwhy humans evolved we have to knowwhen, where, how and from what wearose. Scientists commonly look to livingapes for anatomical and behavioral in-sights into the earliest humans. There ismuch to be gained from this approach.But living great apes have also evolvedsince their origins. The study of fossilgreat apes gives us both a unique view ofthe ancestors of living great apes and hu-mans and a starting point for under-standing the processes and circumstances

that led to the emergence of this group.For example, having established the con-nection between European great apes andliving African apes and humans, we cannow reconstruct the last common ances-tor of chimps and humans: it was aknuckle-walking, fruit-eating, forest-liv-ing chimplike primate that used tools,hunted animals, and lived in highly com-plex and dynamic social groups, as do liv-ing chimps and humans.

Tangled BranchesWE STILL HAVE MUCH to learn. Manyfossil apes are represented only by jawsand teeth, leaving us with little or no ideaabout their posture and locomotion,brain size or body mass. Moreover, pale-ontologists have yet to recover any re-mains of ancient African great apes. In-deed, there is a substantial geographicand temporal gap in the fossil record be-tween representatives of the early mem-bers of the African hominid lineage in Eu-rope (Dryopithecus and Ouranopithecus)and the earliest African fossil hominids.

Moving up the family tree (or, moreaccurately, family bush), we find moreconfusion in that the earliest putativemembers of the human family are not ob-viously human. For instance, the recent-ly discovered Sahelanthropus tchadensis,a six-million- to seven-million-year-oldfind from Chad, is humanlike in havingsmall canine teeth and perhaps a morecentrally located foramen magnum (thehole at the base of the skull throughwhich the spinal cord exits), which couldindicate that the animal was bipedal. YetSahelanthropus also exhibits a number ofchimplike characteristics, including asmall brain, projecting face, sloped fore-head and large neck muscles. Anothercreature, Orrorin tugenensis, fossils ofwhich come from a Kenyan site dating tosix million years ago, exhibits a compa-rable mosaic of chimp and human traits,

as does 5.8-million-year-old Ardipithecusramidus kadabba from Ethiopia. Each ofthese taxa has been described by its dis-coverers as a human ancestor [see “AnAncestor to Call Our Own,” by KateWong; Scientific American, January].But in truth, we do not yet know enoughabout any of these creatures to saywhether they are protohumans, Africanape ancestors or dead-end apes. The ear-liest unambiguously human fossil, in myview, is 4.4-million-year-old Ardipithecusramidus ramidus, also from Ethiopia.

The idea that the ancestors of greatapes and humans evolved in Eurasia iscontroversial, but not because there is in-adequate evidence to support it. Skepti-cism comes from the legacy of Darwin,whose prediction noted at the beginningof this article is commonly interpreted tomean that humans and African apes musthave evolved solely in Africa. Doubts alsocome from fans of the aphorism “absenceof evidence is not evidence of absence.”To wit, just because we have not foundfossil great apes in Africa does not meanthat they are not there. This is true. Butthere are many fossil sites in Africa datedto between 14 million and seven millionyears ago—some of which have yieldedabundant remains of forest-dwelling ani-mals—and not one contains great ape fos-sils. Although it is possible that Eurasiangreat apes, which bear strong resem-blances to living great apes, evolved inparallel with as yet undiscovered Africanancestors, this seems unlikely.

It would be helpful if we had a morecomplete fossil record from which to piecetogether the evolutionary history of our ex-tended family. Ongoing fieldwork promis-es to fill some of the gaps in our knowl-edge. But until then, we must hypothesizebased on what we know. The view ex-pressed here is testable, as required of allscientific hypotheses, through the discov-ery of more fossils in new places.


Function, Phylogeny and Fossils: Miocene Hominoid Evolution and Adaptations. Edited by DavidR. Begun, Carol V. Ward and Michael D. Rose. Plenum Press, 1997.

The Primate Fossil Record. Edited by Walter Carl Hartwig. Cambridge University Press, 2002.

Rudabánya: A Late Miocene Subtropical Swamp Deposit with Evidence of the Origin of the AfricanApes and Humans. László Kordos and David R. Begun in Evolutionary Anthropology, Vol. 11, Issue 1,pages 45–57; 2002.


a dark layer of sediments suggestive of a highorganic content often associated with abundantfossils. That layer was visible in a north-southcross section of the site, becoming lighter and, Ithought, less likely to have fossils, toward thenorth. I asked Hungarian geologist and longtimeamateur excavator Gabor Hernyák to start on thenorth end and work his way south toward thepresumed pay dirt. But within less than a minute,Gabor excitedly summoned me back to the spotwhere I had left him. There, in what appeared tobe the fossil-poor sediment, he had uncovered atiny piece of the upper jaw of Dryopithecus. Bythe time we finished extracting the fossil, we hadthe most complete cranium of Dryopithecus everfound and the first one with the face stillattached to the braincase (bottom).

This skull from Rudabánya—dubbed “Gabi”after its discoverer—illustrates more clearlythan any other specimen the close relationbetween Dryopithecus and the African apes. Iwill always remember the look on my friend andco-director László Kordos’s face when I wentback to the village. (I made the 15-minute cartrip in five minutes at most.) He was in themiddle of e-mailing someone and looked up,quite bored, asking, “What’s new?” “Oh, nothingmuch,” I replied. “We just found a Dryopithecusskull.” —D.R.B.


Every day our neighborhood appears a bit more crowd-ed—and dangerous. The band between Earth and Marshosts swarms of swift-moving asteroids, some of whichmight eventually threaten our planet. The inner solarsystem is home to an estimated 1,000 to 1,500 aster-oids a kilometer or greater in width, with perhaps a

million rocks 50 meters and larger. Asteroid observa-tions pour in at the rate of 15,000 or more a day.

The burden of keeping track of near-Earth objects(NEOs)—asteroids and the occasional comets that passthrough our vicinity—falls on Brian Marsden. Since1978 he has directed the Minor Planet Center (MPC)at the Smithsonian Astrophysical Observatory in Cam-bridge, Mass. Sky watchers from all over the worldsend putative sightings to the MPC, which operates onbehalf of the International Astronomical Union (IAU).The MPC processes and organizes data, identifies ob-jects, computes orbits, assigns tentative names and dis-seminates information on a daily basis. For objects ofspecial interest, the center solicits follow-up observationsand requests archival data searches. “We are the focalpoint,” Marsden says. “All the observations come here.”

Marsden has served as the referee for all NEOsightings over the past 25 years—a period in which thetotal search effort has grown from a fledgling survey ortwo into a productive and efficient international net-work. At times this role has put him in the middle ofcontroversy. Perhaps the most notorious incident oc-curred on March 11, 1998, when Marsden indicatedon the MPC Web site that an asteroid discovered in De-cember 1997 (then named 1997 XF11 and now calledasteroid 35396) would make a close approach in 30years. “The chance of an actual collision is small,” hewrote, “but one is not entirely out of the question.”That phrase set off a media circus that ranked amongthe 20 top science debacles of the century, according toDiscover magazine.

Marsden admits that his word choice was “ill ad-vised” but insists the calculation was correct at thetime. He emphasized its uncertainty in the original no-tice and asked for more data. When the computationswere redone a day later, incorporating orbital infor-mation from an old photograph, the threat vanished.

“Much as the incident was bad for my own reputa-tion, we needed a scare like that to bring attention to


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Keeper of the ObjectsWith a shoestring budget, asteroid and comet watcher Brian Marsden looks out for Armageddon from the skies—and not without controversy By STEVE NADIS

■ On national security: “There’s a lot of concern about security these days,but does it go beyond terrorism and extend to outer space?”

■ On the power of fear: “I think a good scare is occasionally helpful.”■ Of 42 near-Earth asteroids with nonzero impact risk, only one object,

1997 XR2, warrants careful monitoring. See http://neo.jpl.nasa.gov/risk/

BRIAN MARSDEN: HEADS UP ON DANGER

INSIGHTS



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this problem,” Marsden remarks. “Many wondered whether I’dsurvive, but I’m still here.” More important, he says, the field it-self has prospered. In the wake of XF11 publicity, NASA in-creased funding for asteroid searches from $1 million to $3.5million annually. In addition, groups at the University of Pisa inItaly and the Jet Propulsion Laboratory in Pasadena, Calif., be-gan doing routine risk evaluations of potentially menacing ob-jects. To date, the confirmed NEO total includes about 2,250asteroids, a dozen comets that complete their orbits in less than200 years, and 1,000 long-period comets (on orbits 200 yearsor longer) that pose no immediate concern.

It’s a far cry from the early 1960s, when Marsden startedadding to the list of some two dozen known NEOs with detec-tions he made as a Yale University graduate student. After earn-ing his Ph.D. in astronomy in 1965, he took a job at the Smith-sonian, where he has worked ever since.

When Marsden began studying minor planets, “nobodycared about asteroids. They were dismissedas ‘vermin of the sky.’” Now the study is abona fide field, thanks to automated searchprograms such as the Lincoln Near-Earth As-teroid Research (LINEAR), run by the Mas-sachusetts Institute of Technology LincolnLaboratory, and NASA’s Near-Earth AsteroidTracking (NEAT), which collectively accountfor 90 percent of all NEO detections. TheMPC is hard-pressed to keep up with the tideof incoming data, especially with a volume ofmain-belt asteroid observations 100 times asgreat as that for NEOs.

Despite the workload, the MPC staffconsists of only 2.5 people, including Marsden, who would liketo keep the center running 24 hours a day. But that is not fea-sible: MPC gets just $130,000 a year from NASA, despite theagency’s increased spending on NEO surveys. Other income,from subscriptions and donations, is not enough to cover the80- to 100-hour workweeks. “Here we are saving the world,and they expect us to do it on our own time,” Marsden quips.

More draining than the task at hand, however, is the timewasted on arguments. “There’s a lot of infighting in this busi-ness. Not everybody likes everybody,” he says. Besides the XF11affair, which soured his relationships with several colleagues,Marsden has taken heat over access to information. He wouldrather not release data for tentative, single-night asteroid sight-ings—“one-night stands,” as he calls them—both to ensure thedata’s reliability and to conform to the policies of leading pro-grams such as LINEAR, NEAT and Spacewatch, which do notwant unsubstantiated data made public. Astronomers who areanxious to see everything blame Marsden for impeding the in-formation flow. “Brian follows the rules [set by the IAU], but

the rules are flawed,” Lowell Observatory astronomer TedBowell complains. He states that Marsden and others “oftenpost orbital predictions without sharing the data that led to thecalculations. I find that scientifically unacceptable.”

Despite such criticism, the IAU recently extended the Smith-sonian’s contract for running the MPC through 2006. As forbeyond that, rumors swirl about “hostile takeovers,” in Mars-den’s words. Grant Stokes, who heads the LINEAR program,thinks that moving the MPC to a new home would be a mis-take. “Brian and his center service the observing communitywonderfully,” Stokes says. “It’s hard for me to believe this ef-fort could be duplicated elsewhere.”

Marsden tries to ignore the squabbles as he looks to the fu-ture. One day, inevitably, there will be a NEO on a collisioncourse with Earth. With luck, it will be small and won’t causemuch damage. If it is spotted years or decades in advance, theremight be time to intervene. “This is one threat we can do some-

thing about,” he declares. Various defensivestrategies have been proposed, includingnudging an approaching asteroid with a nu-clear blast or darkening part of the object’ssurface so that the thrust produced by radi-ated heat changes its orbit. Marsden is notsure how much money should be spent ex-ploring these options but insists that “wehave to do more than the dinosaurs.”

Until now, the focus has been on largeasteroids, a kilometer or bigger. The goal ofthe Spaceguard Survey, funded mainly byNASA, is to find 90 percent of these objectsby 2008. More than 650 asteroids have

been identified so far, perhaps half the total. (Astronomers es-timate the total based on discovery rates from previous sur-veys.) Still, Marsden remarks, “we should begin planning thenext step.” Looking for 200- to 300-meter-wide objects is of-ten proposed as a sensible target, but that would require newtelescopes and roughly 10 times as much money.

Marsden turns 66 this month and would eventually like tohand the reins over to MPC’s associate director, GarethWilliams, his partner since 1990. There’s no timetable for atransition, says Williams, who admits he has “very big shoes tofill. Brian has been preeminent in the field since the 1960s.”NASA Ames astronomer David Morrison, chair of the IAU’sNEO working group, also lauds Marsden’s efforts. GivenMarsden’s long tenure in the NEO field—starting out as he didwhen there was no “field” to speak of—Morrison is skepticalabout talk of his impending retirement: “I think he’ll do it for-ever.” That is, of course, if the world doesn’t end first.

Steve Nadis is a science writer based in Cambridge, Mass.


COLLISIONS with even small NEOs pose athreat: an object only 100 meters wideflattened these trees in Siberia in 1908.


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NIGHT VISION

Humans cannot see in the dark, yet millions of tele-vision viewers regularly saw green, ghostlike tanks,soldiers and reporters negotiate the desert blacknessduring the recent Iraq war. Night vision tubes builtinto video cameras made it possible—the same tech-nology that outdoor enthusiasts use to spot nocturnalanimals or buoys on midnight waters and that policeuse to observe crooks in shrouded doorways.

No matter how dark the night, the stars, moon andman-made fixtures supply a small number of photonsthat such instruments can detect. The gear, which wasinvented during World War II by the military and hassince trickled down to consumers, has advanced in“generations”: rough standards of effectiveness de-fined by the U.S. Army Night Vision Labs at FortBelvoir, Va. By the late 1980s, generations one andtwo gave way to the prevailing “Gen 3” products. Un-der a quarter moon (0.01 lux of light), they can dis-tinguish a six-foot-tall person at 600 yards; qualitymonoculars cost $2,000 to $3,500.

The heart of any device is an intensifier tube thatconverts scarce photons into electrons and then am-plifies and converts them into a visible image. Thetubes do degrade—the best offer 10,000 hours of op-eration—but can be replaced. They are also limited, ifnot ineffective, in smoke, sandstorms and fog. For thatreason, some soldiers use infrared goggles that capturethe heat gradients of an enemy or vehicle—or the resid-ual heat gradient left by one that recently passed by—

and render a black-and-white image. The image sharp-ness is far less clear than night vision tubes, and if ob-jects in a scene are at a uniform temperature—such asa pothole and a road—nothing appears. But infraredinstruments can detect objects several miles away.

Manufacturers are thus beginning to produce pro-totypes of “fused” goggles that can overlay an infraredimage onto a green intensifier-tube image. “I believethis will constitute the next generation of night vision,”says Tom Peck, vice president of manufacturing engi-neering at ITT Industries Night Vision in Roanoke,Va., the U.S. military’s dominant supplier. Then, al-though we will still live half our lives at night, we willnever be in the dark. —Mark Fischetti

Seeing Green

WORKINGKNOWLEDGE

MONOCULAR LENS focuses the precious few photons available indarkness onto an intensifier tube, which is under vacuum. Inside, a photocathode (1) converts photons to electrons. A voltageaccelerates the electrons to the microchannel plate (2), only afew thousandths of an inch (mils)—the thickness of two sheets ofpaper—away. The plate multiplies the electrons, and a secondvoltage accelerates them to the phosphor screen (3), again only a few mils away. It converts electrons back into photons that reach the eyepiece.

Intensifier tube

Photon

Lens

1

2

3

86 S C I E N T I F I C A M E R I C A N A U G U S T 2 0 0 3COPYRIGHT 2003 SCIENTIFIC AMERICAN, INC.

➤ 6,000-VOLT CHALLENGE: The photocathode, microchannel plate

and phosphor screen inside an intensifier tube nearly touch, yet the

voltages that accelerate electrons across the tiny gaps between

them range from 500 to 6,000 volts. “The greatest engineering chal-

lenge is keeping these parallel plates so close together yet so clean

that we can apply such high voltages without any breakdown,” says

Tom Peck of ITT Industries Night Vision. Two AA batteries can provide

the steep voltages at extremely low currents, using power-supply

conversion circuitry, for 50 to 60 hours.

➤ MOUT CLOUT: Early generation-three instruments have trouble

maintaining an image where lighting varies greatly, such as a city, re-

ducing their effectiveness for soldiers engaged in so-called military

operations in urban terrain (MOUT). By gating voltages and lowering

currents inside the intensifier tube, manufacturers have increased

the dynamic range of the devices. Now a soldier can spy a foe hiding

in a dark shadow in a streetlit alley and keep a fix on him if the head-

lights of a passing car suddenly alter the scene.

➤ CAN’T SELL THIS: Night vision monoculars, binoculars, goggles,

cameras, gun sights and other gear are “restricted for export” by the

U.S. State Department. Any person or company selling or sending the

technology abroad without licensing authorization could face severe

fines and even time in prison.

DID

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Oxide filmGlass

Microchannel

Oxide film

Aluminumgallium

arsenide

Antireflective coating

Glass

Galliumarsenide

Metal film

Phosphorparticles

Glass

Eyepiece

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PHOTOCATHODE’S LAYERS, only a few microns thick,are struck by photons. Their energy kicks out electrons.Gallium arsenide responds strongly to thepredominantly red and near-infrared frequencies oflight radiated by the night sky.

MICROCHANNEL PLATE has millions of tiny, slanted channels.Electrons enter and bounce off channel walls. Each collisionproduces two or three more electrons, multiplying the initialnumber many times. A film prevents positive ions created bysome collisions from streaming back to the photocathode,which would degrade it. A voltage across the plate moveselectrons through the microchannels.

PHOSPHOR SCREEN emits a visibleimage as accelerated electrons strike,exciting phosphor particles, much likea cathode-ray tube. A film preventsphotons from reflecting toward thephotocathode, which would causedestructive feedback.

NIGHT VISION IMAGES are green because phosphors in the instrumentsemit light near the green wavelength of 550 nanometers, which is the“photopic maximum” for the human eye—the wavelength at which the eyeis most sensitive, optimizing the brain’s perception of contrast.


This month’s topic was suggested by reader Chris Connor. Send your ideas to [email protected]

Electron

I T T I N D U S T R I E S N I G H T V I S I O N


Convergence—the notion that comput-ers, televisions, stereos and telephoneswould all become one—was the buzz-word du jour a decade ago. Media andcomputer executives were quite takenwith the “multimedia PCs” that had justcome out, and many fancied that com-puters would soon be so capable that theywould become the natural hub of com-munications and entertainment in thehome. But the technology was actually notthat capable, and the executives weresoon distracted by a new fad calledthe Internet.

Now convergence is back,with grand pronouncementsby Philips, Pioneer, Sam-sung and other big gadgetmakers promising thattheir forthcoming prod-ucts will make our sofa-bound hours of enter-tainment that muchmore pleasurable. Com-munications, in this go-round, has been shovedto the backseat. The cur-rent thinking is that con-sumers will not add thesenovel devices, referred to ashome media servers or digi-tal media receivers, to their al-ready cluttered entertainmentcenters because the gear is useful.They will buy the things because theyare fun.

Fun is a hard quality to design, espe-cially for computer engineers. Fun thingsjust work; they do not frustrate. Design-ers of digital media toys face a double dif-

ficulty. First they must make the circuitryand software simple and reliable enoughthat couch potatoes can control themfrom a handheld remote while half-asleep.Then they must teach the machines to un-derstand a babel of media formats, someof them encrypted with so-called digital-rights management codes. Viewers willbe annoyed if restrictive copy prevention

schemes thwart them from watching orlistening to programs they have alreadypaid for.

How well do the first entrants in thearena succeed in engineering the absenceof annoyance? To find out, I spent sever-al weeks with three network media appli-ances. Two of the devices are made by gi-ants Sony and Hewlett-Packard. But thethird is made by a young start-up namedPrismiq, and as often happens, the entre-preneurs have been the most innovative.

The three gadgets are similar in sever-al ways. Each runs $200 to $250, con-

nects to your Ethernet network, andplugs into the TV and stereo—or

just to the television if no stereo ishandy. (Pricier models can beused with wireless WiFi net-works as well.) Each movesdigital media that you alreadyown from your computers toyour speakers and screens.So there is no monthly sub-scription fee, unlike TiVo.And each receiver comes withsoftware that allows yourcomputers to act as “servers,”

streaming photographs, musicand other digital media to the

receivers.Sony, the master of miniatur-

ization, squeezed its RoomLink Net-work Media Receiver into an elegant

case the size of a hefty paperback. But thetest gear from Sony arrived in three box-es weighing 20 kilograms. That is becausethe RoomLink works only with Sony’sown Vaio line of PCs. If, like me, you donot already own a Vaio, the effective price

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Converging on the CouchNEW DEVICES CONNECT THE STEREO AND TV TO THE HOME DATA NETWORK BY W. WAYT GIBBS

“POINT AND CLICK” takes on new meaning withremote-controlled digital media receivers.


of a RoomLink is not $200 but closer to$2,000.

Sony aims its Vaio computers at mediacreators, the sort who shoot their own dig-ital movies and burn them to DVD. Suchpower users may appreciate the three fea-ture-rich programs that one has to use onthe PC to identify the MP3 files, photo-graph directories and video recordingsthat the RoomLink will offer in its menus.But each program has a dramatically dif-ferent interface, and I found all the op-tions confusing. It took about an hour offiddling and reading the manuals to set upmy playlists on the Vaio in the attic.

Three stories down in the familyroom, I grabbed the remote, turned onthe RoomLink, selected the attic Vaio PCas the server (a curious and tiresome step when there is only one choice) andthen started a photo slide show. This is

where the fun began. Family snapshots are immeasurably more entertaining whenviewed on television. Whether it is becausethey are brighter, larger and more vibrantthan are prints in an album, or whether itis the weird sense of fame produced by see-

ing yourself and your loved ones on TV,I can’t say. But it may be habit-forming.

After a week of use, however, little an-noyances undermined the fun coolness ofthe RoomLink. The Vaio PC comes witha built-in video recorder. So while watch-ing TV in the family room, a press of the“record” button saves the show to harddisk for later viewing. The RoomLinkwill also play movies copied directly to

the Vaio from a personal video camera. But it will not play video clips from

other sources—downloaded from theWeb, for example. The software refusedto run any of the home movies I had madeusing our digital camera and (non-Sony)

computer. In its zeal to discourage illegalcopies of commercial films, Sony’s videosoftware cut me off from movies of myson eating his first solid food.

The HP Digital Media Receiver is assimple as the Sony is sophisticated. It doesonly two things—photos and music—butit does them well. The software installedquickly, asked which media folders tomonitor, and then disappeared; I never


Slide shows with soundtracks are definitely addictive. But are they

enough fun to justify the cost?


had to touch it again. Media files fromboth of my Windows PCs magically ap-peared in the menus without any irritat-ing “select server” screens. (None of thethree receivers were able to work with mythird computer, which runs Linux, nor dothey support Apple’s Mac OS.)

The receiver automatically catego-rized the more than 600 MP3 music fileson my machines by artist name, album ti-tle, even genre. And unlike the Sony, theHP gadget could play music in the back-ground while displaying all the photos ina folder. Slide shows with soundtracks aredefinitely addictive. But are they enoughfun to justify the $200 cost?

Personally, I expect $200 to buymore. A new version of the Prismiq Me-diaPlayer released in May, for example,plays music and photos simultaneously.But the MediaPlayer comes with a key-board and has a simple built-in Web

browser that I used to check e-mail,weather reports, movie times and restau-rant reviews. The Prismiq can play Inter-net radio stations. I listened to one fromIran and another from Russia. The high-ly compressed radio music falls short ofthe CD quality of music files from my owncomputers, but it was thrilling to tune inmusic from halfway around the planet.

And the MediaPlayer can run videos—

not merely the homemade variety but alsomovies downloaded from the Internet oreven from DVDs. My wife and I watchedthe video of our son pushing his littlespoon out of his mouth over and over, asJohnny Cash’s song “Bonanza” played inthe background.

But here the Prismiq device, too, getstripped up by the recording industry’sself-inflicted limitations. The MediaPlay-er can display only unencrypted videofiles. Because DVD movie files are en-

crypted, that means using special soft-ware that cracks their codes and copiesthem to a hard disk. Such software ap-pears to violate the Digital MillenniumCopyright Act. And yet the software isreadily available and, ahem, is compati-ble with the Prismiq receiver.

Wouldn’t it be fun to download amovie rental—from a service such asMovieLink, for example—and watch itfrom the couch rather than the computerchair? I tried it; it doesn’t work. By design,MovieLink stored the films I rented anddownloaded in an encrypted file formatthat will not play on any of the media re-ceivers. To watch A River Runs ThroughIt on the television, I had to connect longcables from my computer to the stereo andTV, then fuss with Windows for half anhour to get the player software to showthe movie on the correct screen. And sofrustration trumps fun once again.


TECHNICALITIES


REVIEWS

Is Mars letting us down?In the 1980s and early 1990s, many plan-etary scientists got the sinking feeling thatthe Red Planet wasn’t living up to hu-manity’s expectations. Its surface waslifeless, its volcanoes extinct. Evidence ofan Earth-like past was looking shaky.When I entered graduate school in plan-etary science during this period, I was dis-couraged from doing research on Mars,as the data from the Viking spacecraft ofthe mid-1970s had been thoroughlypicked over. Follow-up missions fromthe U.S. and the Soviet Union floundered.Scientists found themselves pitted against“Face on Mars” conspiracy theorists intelevision debates.

Even through these dark years, veter-an researcher William K. Hartmann heldthat Mars was not, in fact, geologicallydead. He reasoned that some of the ter-

rain was so fresh, so free of meteorcraters, that at least some of the volcanoeswere not extinct, merely dormant. It wasa minority view—but no longer. Newspace missions have found signs not justof recent volcanism but of glaciers, liq-uid water and periodic climate change.Things are looking up again for the RedPlanet, and Hartmann’s latest book en-capsulates this understanding.

The author, who works at the Plane-tary Science Institute in Tucson, Ariz., hasbeen around long enough to see sentimentabout Mars go through several cycles ofbust and boom. He recalls the first obser-vations by the Mariner 9 spacecraft in1971. Its predecessors had already dashedhopes of a world covered in vegetation,and the global dust storm that greetedMariner 9’s arrival deepened the gloom.But as the dust cleared, a mountain withno equal in human experience—so bigthat it would span the state of Missouri—slowly came into view: Olympus Mons.The outlines of a sublime canyon systemgradually took shape: Valles Marineris. Itwas as if the dust had erased all those pri-or expectations and allowed Mars to re-veal itself on its own terms.

Hartmann’s book is being marketed

as a travel guide, but it is best thought ofas an extended argument for the persis-tence of geologic activity. The main con-cession to the guidebook conceit is its re-gion-by-region approach. Going (rough-ly) from the oldest terrain to the youngest,the book provides a close reading of themost scientifically and aesthetically com-pelling images. It shows how planetarygeologists reconstruct Martian history bylooking at the relationships among for-mations: whether a crater punctures alava flow, say, or a sand dune covers acrater floor. The book includes a numberof photographs of similar-looking forma-tions on Earth, as well as interpretivepaintings. (Hartmann is a well-known as-tronomical artist.)

Mixed in with this analysis are primerson geologic processes; the explanations ofimpact cratering and the stability of liq-uid water are models of elegance. Thebook hits pretty much every aspect ofMartian surface science. (For the interior,atmosphere and natural satellites, you’llneed to turn elsewhere.) A series of box-


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Better Red Than DeadA VETERAN RESEARCHER MARSHALS EVIDENCE THAT MARS IS GEOLOGICALLY ALIVE BY GEORGE MUSSER

A TRAVELER’S GUIDE TOMARS: THE MYSTERIOUSLANDSCAPES OF THE RED PLANET by William K. Hartmann Workman Publishing, New York, 2003 ($18.95)

Christiaan Huygens, 1659 Giovanni Schiaparelli, 1888 Telescopic view, early 1960s Hubble Space Telescope, 1997 Mars Global Surveyor, 2002

VIEWS OF MARS have progressed from visualsketches to detailed photographs. These imagesall show roughly the same area, Syrtis Major.


es give personal reminiscences and com-mentary on subjects such as the braindrain caused by the lack of jobs for youngscientists, a situation with which my gen-eration is all too familiar.

Although the book isn’t technical, itsnarrative is probably too nonlinear for anabsolute beginner. The structure is un-even. Some chapters are fleshed out stepby step; others flit over important ques-tions, as if topics are being force-fit intothe region-by-region approach. The textoccasionally falls into the same trap aswritings by many other scientists andjournalists—something I call the re-ceived-wisdom syndrome. In one exam-ple, chapter 25 states that because aster-oids formed 4.5 billion years ago, almostall meteorites are 4.5 billion years old.How do scientists know that? To ex-plain, the sentence should be flippedaround: “Because almost all meteoritesare 4.5 billion years old, asteroids musthave formed that long ago.”

A beginner may also have trouble in-terpreting the images. The captions makereference to shorelines, landing sites,mountain ranges, river bends, plateaus.But few images have labels or arrows toindicate exactly where these features are.The fold-out global maps are skimpy, butthat is easily solved by reading the bookalongside either the map in the February2001 issue of National Geographic or theone put out by the U.S. Geological Survey(astrogeology.usgs.gov/Gallery/MapsAndGlobes).

Someone who already knows the ba-sics about the Red Planet will read rightpast these hiccups, and the reward is analmost participatory experience, givingan intimacy with the planet and with theway a planetary scientist thinks. As Hart-mann writes in the introduction, most re-cent Mars images “have not been studiedin detail, and readers of this book will beamong the first human beings to studysome of the ones chosen here.”

George Musser covers astronomy forScientific American.

ART FOR SCIENCE

WASTE NOT/WHAT NOT CATALOGby Gaza Bowen. Cackling Crones Press, Santa Cruz, Calif., 2002 ($10, paperbound)ARCHAEOLOGYEdited by Alex Coles and Mark Dion. Black Dog Publishing, London, 1999 ($19.95, paperbound)MINUS SIXTEENby Robin Broadbent. Browns, London, 1998 ($40)Art has often illuminated science with its brevity, its wit and its beauty. Printed Matter, anorganization devoted to making artists’ books better known, provides some intriguing re-cent examples of this contribution. At the “wit”end of the spectrum is Bowen’s Waste Not/What Not Catalog, a parody of a mail-order cat-alogue based on her tenure as artist-in-resi-dence at the San Francisco dump. The book mir-rors a technological society whose waste is outof control, stunning readers with photographsof what we throw away and introducing them tosuch concepts as zero waste, cradle-to-cradledesign and embodied energy. Artist Dion’s ar-chaeology projects—the History Trash Dig,Raiding Neptune’s Vault and the Tate ThamesDig—are chronicled in Archaeology, which in-cludes a fascinating essay by University ofCambridge archaeologist Colin Renfrew (“It MayBe Art but Is It Archaeology?”) that analyzes theway Dion dissolves the boundaries between artand science. And there is beauty, too. Minus Six-teen—Broadbent’s gorgeous, grainy black-and-white photographs of the surface of a Scot-tish lake, where plunging overnight temperatures create ice layered with alien forms andtextures—gives us the universe, as it were, in an ice crystal.

All available directly from Printed Matter: www.printedmatter.org

VIRTUAL ART: FROM ILLUSION TO IMMERSIONby Oliver Grau. Translated by Gloria Custance. MIT Press,Cambridge, Mass., 2003 ($45)The computer’s ability to immerse a user in virtual imagespaces “is not the revolutionary innovation its protagonistsare fond of interpreting it to be,” Grau writes. “The idea of vir-tual reality only appears to be without a history; in fact, itrests firmly on historical art traditions.” Grau (lecturer in arthistory at Humboldt University in Berlin, associate professorat the Kunstuniversität Linz in Austria and leader of the Ger-man Science Foundation’s project on immersive art) tracesthe lineage of virtual reality as far back as the frescoes of avilla in Pompeii. Many illustrations amplify the argument.

This book and A Traveler’s Guide to Mars are available for purchase throughwww.sciam.com

THE EDITORS RECOMMEND


REVIEWS

LOOT 2, by Mark Dion (from Archaeology)



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PUZZLINGADVENTURES

Imagine you are a government official with con-fidential messages to send. But spies want to inter-cept the messages. To tap a certain microwave link,your opponents must be in the line of sight of thetransmitter. This positioning puts them in dangerof detection and arrest, so you are sure they will at-tempt the job only once and for no more than 10minutes. The trouble is, you don’t know which 10-minute intervals they will choose.

You have seven messages, labeled alphabeti-cally, to send in as short a time as possible. Theirlengths are:

A : 2 minutesB : 3 minutesC : 4 minutesD : 5 minutesE : 6 minutesF : 7 minutesG : 8 minutes

You will accept having the spies intercept up tothree of these communiqués. You consider a mes-sage to be intercepted if it is tapped from start to

finish; a partly tapped message won’t do them anygood. You must send each message in one contin-uous transmission, but you can transmit as manyas you like in parallel and can begin sending oneor more messages while others are still being sent.

To warm up, suppose you can accept the ene-my spies’ tapping only one complete message.When should you send each message to minimizethe total time? See the illustration below for a 36-minute solution.

Because you allow up to three messages to betapped in the main problem, you may be able to re-duce the time considerably. Can you find a way tosend the seven messages in 15 minutes or less? If inaddition to these seven messages, you had to sendthree four-minute messages without having morethan three of the 10 tapped in their entirety, couldyou do it in 20 minutes or less?

Dennis E. Shasha is professor of computerscience at the Courant Institute of New YorkUniversity. His latest book is Dr. Ecco’sCyberpuzzles: 36 Puzzles for Hackers and OtherMathematical Detectives (W. W. Norton, 2002).

Short Taps BY DENNIS E. SHASHA

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36

B......... A......

C..............D.................

E.....................F......................... G............................

Time (minutes)

Answer to LastMonth’s PuzzleAt least one and at most threecontainers of goodstravel from country Ato country D. CountryE receives at mosttwo containers from Aand possibly none. In the secondproblem, D gets atmost threecontainers from A butpossibly none. Theminimum andmaximum numbersfrom A arriving at E do not change.

Web SolutionFor a fullerexplanation of lastmonth’s solution anda look at the answerto this month’sproblem, visitwww.sciam.com

A WARM-UP SOLUTIONTo send all the messages in 36 minutes with no morethan one of them getting intercepted, transmit B at 0 minutes, followed by F at 4, D at 10, G at 13, C at 20,

E at 25, and A at 34. No 10-minute interval will containtwo messages in their entirety. You may be able todiscover a better solution.

Sender

Spy


ANTIGRAVITY

The dog days of August are upon us.What could be more of a distraction fromthe summer swelter than the shelter of afamiliar exercise ordinarily reserved forthe academic year? Therefore, it’s time forthat old favorite, the true-or-false quiz.(Don’t worry, I’ll write the essays.)

1. Einstein and Newton may have hada form of autism.

True, according to one autism re-searcher. New Scientist reports that SimonBaron-Cohen of the University of Cam-bridge thinks that the two great physicistsmight have had a form of autism calledAsperger syndrome. Markers for the syn-drome include an obsessive focus on asubject of interest, poor relationships andcommunication difficulties. (But of course,those symptoms also describe millions ofpeople who listen to hours of sports talkradio every day.) By the way, a newspa-per article on Baron-Cohen’s theory notesthat “firm diagnosis on the dead is im-possible,” which I disagree with, becauserigor mortis is about as firm a diagnosisas there is.

2. A 17-year-old boy in Nuremberg,Germany, is capable of teleportation.

False. The boys claiming to be thepossessors of this extraordinary abilitywere really identical evil twins. One ofthe twins would demand money fromsmall children, who would turn and fleefor a block or so, only to run into whatthey took to be the very bully they’d justescaped. In May a court told the dupli-cate delinquents to stop doppelgängingup on people.

3. Scientists proved that an infinitenumber of monkeys on an infinitenumber of typewriters will composethe complete works of Shakespeare.

False. But researchers at PlymouthUniversity in England showed that six Su-lawesi crested macaques with access to acomputer for four weeks at a zoo willproduce a tale told by an idiot. Accordingto a May wire service report, the com-

puter was placed in the monkey enclo-sure, where “the lead male got a stoneand started bashing the hell out of it.” (Apalpable hit.) “Another thing they wereinterested in,” a researcher said, “wasdefecating and urinating all over the key-board.” (It smells of mortality.) They alsopressed the “s” key a great deal forssssssssome reason. The clacking ma-caque project was paid for with a grantfrom England’s Arts Council, which willpublish the monkey literary efforts as

Notes towards the Complete Works ofShakespeare. The U.S. National Endow-ment for the Arts is rumored to be com-ing out with a companion volume,Thrilled We Didn’t Fund It.

4. In April the CIA decided to classifya report on a January session inwhich microbiologists and the CIA’sstrategic assessment groupdiscussed scientific openness.

True. That popping sound was yourhead exploding.

5. Phosphatase enzymes expeditethe breakdown of phosphatemonoesters in about 10 milliseconds.Without the enzyme, the reaction’shalf-life would be a trillion years.

True. Richard Wolfenden, an enzymemaven at the University of North Carolinaat Chapel Hill, and his colleagues pub-lished that finding in a recent Proceedingsof the National Academy of SciencesUSA. Here’s an easy way to appreciatehow long a trillion years is. If you paid offthe national debt at one dollar a year, itwould take 6.4 times as long as the half-life of the enzyme reaction. Fortunately,you don’t have to worry about a race be-tween exceedingly slow biochemistry andunbelievably torpid debt relief, becausewe’re lucky enough to have enzymes, andthe debt is actually getting bigger.

6. Football players at Giants Stadiumin New Jersey run on old sneakers.

True. The stadium’s new fake grass ismade from recycled sneakers. I learnedthis listening to sports talk radio.


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This Is Only a TestAN INTERACTIVE LOOK AT SOME RECENT SCIENCE STORIES IN THE NEWS BY STEVE MIRSKY


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Mark Shegelski, professor of physics at the University ofNorthern British Columbia, offers this answer:

Theoretically, yes. For this conjectural trip, let us ignore fric-tion, the rotation of the earth and other complications. Just pic-ture a hole or tunnel that enters the earth at one point, goesstraight through the center and comes back to the surface at theopposite side of the planet. If we treat the mass distribution inthe earth as uniform (for simplicity’s sake), a person could fallinto the tunnel and then return to thesurface on the other side in a mannermuch like the motion of a pendulum.Assume that the person’s journey be-gan with an initial speed of zero kilo-meters an hour (he simply droppedinto the hole). His speed would in-crease and reach a maximum at thecenter of the earth, then decrease un-til he reached the surface—at whichpoint the speed would again fall tozero. The gravitational force exertedon the traveler would be proportionalto his distance from the center of theearth: it is at a maximum at the surfaceand zero at the center. The total triptime would be about 42 minutes. Ifthere were no friction, no energy wouldbe lost, so our traveler could oscillatethrough the tunnel repeatedly.

This jaunt could not occur in thereal world for a number of reasons. Among them: the implau-sibility of building a tunnel 12,756 kilometers long, displacingall the material in the tunnel’s proposed path, and surviving thejourney through a passageway that runs through the earth’smolten outer core and inner core—where the temperature isabout 6,000 degrees Celsius.

Interestingly, if the tube did not pass through the center ofthe planet, the travel time would still be about 42 minutes. Thatis because although the burrow would be shorter, the gravita-tional force along its path would also diminish compared withthat of one that goes through the center of the planet. So the

person would travel more slowly. Because the distance andgravity decrease by the same factor, the travel time ends up be-ing the same.

How do manufacturers calculatecalories for packaged foods?

—S. Connery, Friday Harbor, Wash.

Jim Painter, associate professor and chair of family andconsumer science at Eastern Illinois University, explains:

To answer this question, it helps to first define “calorie,” aunit used to measure energy content. The calorie you see on afood wrapper is actually a kilocalorie, or 1,000 calories. AKcalorie is the amount of energy needed to raise the tempera-ture of one kilogram of water by 1 degree Celsius.

Initially, to determine Kcalories, a given food was placed ina sealed container surrounded by water, an apparatus knownas a bomb calorimeter. The food was completely burned, andthe resulting rise in water temperature was measured. Thismethod, though not frequently used any longer, formed the ba-sis for how Kcalories are counted today.

The Nutrition Labeling and Education Act of 1990 re-quires that the Kcalories of packaged foods be totaled from thefood’s energy-containing components: protein, carbohydrate,fat and alcohol. (Because carbohydrates contain some indi-gestible fiber, the grams of fiber are subtracted as part of theKcalorie calculation.)

All food labels use the Atwater system, which establishes theaverage values of four Kcalories per gram for protein, four forcarbohydrate, nine for fat and seven for alcohol. Thus, the labelon an energy bar that contains 10 grams of protein, 20 of car-bohydrate and nine of fat would read 201 Kcalories. Addition-al information on this subject, and the Kcalorie counts for morethan 6,000 foods, is available on the Nutrient Data LaboratoryWeb site (www.nal.usda.gov/fnic/foodcomp/).

Would you fall all the way through a hypothetical hole in the earth?

—T. Fowler, Snohomish, Wash.

ASK THE EXPERTS

For a complete text of these and other answers from scientists in diverse fields, visit www.sciam.com/askexpert



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