Going on an AntedateA strange history of imperfect perfect proportions.

KENNETH M. WEISS AND JEFFREY A. KURLAND

In the mid-1700s, the English lan-guage was rather out of control. Inthe absence of a satisfactory refer-ence, word meanings were unclear.Even Shakespeare had alreadybecome somewhat obscure to mostreaders. So the intellectual-about-town, Samuel Johnson, convincedinvestors that an English dictionarybased on improved principles wouldbe commercially successful.1–3 Exist-ing dictionaries were based on ‘‘agenealogy of sentiments,’’ as authorhad copied author over time. Instead,Johnson argued for an approach thatreflected ‘‘intellectual history,’’ a termhe appears to have coined (Fig. 1).Appearing in 1755, ‘‘Johnson’s’’ be-came the standard dictionary forabout a century. He showed a word’sevolving meaning by using historicalexamples of its usage.In science as well as literature,

meaning can become blurred overtime. Perhaps even more problematicand harder to trace than word defini-tions are changes in concepts. Aninteresting example is the Hardy-Weinberg principle (HW). Afterteaching the essentials of Darwinianevolution, Mendelian inheritance,molecular biology, and speciation,students are routinely introduced toHW. We teach it as a stable geneticbaseline, the HW equilibrium, devia-

tion from which leads to the changesthat define evolution. However, sinceit will be on the test, many students(even those who are awake) see HWonly as an algebraic threat to theirgrade-point average. As one studentgriped, ‘‘Let me get this straight.When nothing happens . . . nothingchanges? Duh.’’

Over decades of textbooks, HWappears to be taught largely becauseit always has been taught. It’s part ofour pedagogic heritage, but its mean-ing and rationale have become hid-den in the dusty volumes of pastjournal articles. It seems unthinkableto omit it. But why? To see that, wehave to go back to the origin of mod-ern genetics.

FIRST PRINCIPLES FIRST

When Gregor Mendel did his fa-mous experiments with peas, the na-ture of inheritance was unknown.Following an ancient idea, Darwinthought that each organ transmitteda tiny miniature of itself to thegonads and that the ‘‘gemmules’’from each parent blended to formthe offspring. It was quickly shownthat blending didn’t work, but Dar-win’s cousin Francis Galton ad-vanced a modified theory of Ances-tral Heredity: You receive a set ofheritable units from your parents.The fertilized egg uses up half of thatmaterial to construct you as an orga-nism; the remaining half is saved tobe doled out to your children, whoget half their material from you andhalf from your spouse. Thus, yourdirect contribution is cut by half ineach succeeding generation, gradu-ally petering out until there is hardlyany left. This ‘‘biometric’’ theory

explained the inheritance patterns ofquantitative traits like skin color.Mendel’s ideas were different. He

was trained to think that organic na-ture follows the same laws as doesthe physical world of fundamentalparticles.4–6 Inheritance must followmathematical rules. He used hybrid-ization experiments to deduce thoserules from the relative frequency ofalternative traits such as green ver-sus yellow peas. He succeededbecause he deliberately chose traitsknown to breed true in differentstrains of peas, and he showed thatthe rules were general by repeatinghis experiments and testing sevenunrelated traits.Mendel avoided traits with blurry

intermediates, but he did explain afact that also puzzled Darwin andGalton. A trait could disappear inone generation, then reappear in thenext. If yellow and green peas werecrossed, for example, all the off-spring plants bore yellow peas. But ifhe then crossed those plants, thegreen trait would reappear in thenext generation and—a vital clue—the proportions of the two typeswere predictable and repeatable. Inparticular, in the offspring cross hefound his famous 3:1 ratio thatalways favored one trait. He inferredthat a plant inherited nonblendingfactors from each parent, and wasequally likely to transmit either to itsoffspring. In modern terms, if a yel-low-producing allele (variant state) Ais dominant over the green a, theoriginal AA 3 aa (yellow 3 green)cross produces only yellow Aa off-spring. Listing the maternallyderived allele first, when you crossthese with each other, you get equalnumbers of AA, aA, Aa, and aa

CROTCHETS & QUIDDITIES

VVC 2007 Wiley-Liss, Inc.DOI 10.1002/evan20151Published online in Wiley InterScience(www.interscience.wiley.com).

Ken Weiss and Jeff Kurland are in theDepartment of Anthropology at PennState University.

Evolutionary Anthropology 16:204–209 (2007)

offspring. Since only the aas aregreen, that is Mendel’s famous 3:1ratio.

TODAY’S STUDENTS NOT THEONLY ONES CONFUSED

Mendel’s work was recognized in1900, and ‘‘gene’’ was coined by theDanish botanist Wilhelm Johannssenin 1909 to refer to his inherited par-ticles, whatever they are. As SamuelJohnson might find amusing, somany new functional aspects of thegenome have been found that thedefinition has morphed to its latesthardly-helpful incarnation of ‘‘aunion of genomic sequences encod-ing a coherent set of potentially over-lapping functional products.’’7

When we teach old, established,everybody-knows-that concepts, it’seasy to forget that a century agothese were new ideas that solved realscientific conundrums, and in waysthat were not always evident at thetime.Mendel’s 3:1 ratio refers to a single

generation of peas from a breedingexperiment. But if this is a generallaw of inheritance, what would hap-pen over many generations—on theevolutionary scale? This proved to bea surprisingly confusing question inwhich evolution, semantics, and themyopic eye of preconception enteredthe drama. The effect of a genotypeon producing a trait was confusedwith its effect on the competitive fit-ness of the trait. Perhaps, in part,Mendel’s word ‘‘dominirende,’’ or‘‘dominating,’’ suggested a trait’s abil-ity to bully its way to selective vic-tory.4,8 Only later did the translationbecome ‘‘dominant’’ and thereby loseany such evolutionary connotation.Johnson would be pleased. Twoother concepts were confused, thedescriptive word ‘‘proportion’’ andthe action-related word ‘‘probability,’’which still are often confused today.

In 1902, the English statisticianGeorge Udny Yule asked what wouldhappen to Mendelian proportions ifyou hybridized two strains (AA 3aa) and let their descendants ran-domly breed thereafter instead ofsetting up controlled breeding foreach generation. Yule correctlyinferred that under Mendel’s rulesthe classic 3:1 ratio would persist inevery future generation. Since thefounders in Yule’s thought-experi-ment were AA and aa, hence the al-lele frequencies were 0.5, this evolu-tionary result was a not terribly sur-prising extension of Mendel’s ownexperiments. But Yule then askedwhat would happen if only the domi-nant 75% of the population, ratherthan everybody, were allowed tobreed? This would be the kind of ar-tificial selection that agriculturalbreeders had done for centuries, andDarwin used as a model for evolu-tion by natural selection. Yulewrongly calculated that in a few gen-erations the dominants wouldapproach a limiting proportion of85.355339%. This seemed to showthat Galton’s theory was right: Thewimpy recessive trait maystay around, but diluted. But Mendelwas right, too, because the recessivekeeps reappearing. Yule concludedthat Mendel’s principles were a spe-cial case of ancestral heredity for adominant trait.

However, W. E. Castle, the leadingAmerican defender of Mendel’stheory, was delighted to find a mis-take in Yule’s calculation; a realiza-tion showed the failure of Galton’stheory. If selection consistently elimi-nated the recessive every generation,but all possible matings among theremaining dominants are calculated,the dominant will very, very, veryslowly approach 100%. There is nostable proportion of recessives withconstant selection against them.Nonetheless, Castle showed that onceselective breeding against recessives

stops, the then-current ratio of domi-nants to recessives, whatever it is,will remain indefinitely. So depend-ing on when selective breeding stops,there are any number of possible sta-ble proportions. Independently, inEngland, Karl Pearson proved thatthe 3:1 ratio is stable in a random-mating population. But, like Yule, hestarted with equal allele frequenciesand never generalized these resultsto all possible frequencies. The greatstatistician should have done that,but he didn’t.By 1908, confusion was rampant.

A well-known Mendelian, ReginaldPunnett, presented a paper on Men-delism in humans, citing eye colorand brachydactyly (short fingers) asexamples, which puzzled Yule. In arandom-mating population like Eng-land, why didn’t Punnett find a 3:1ratio of brown to blue eyes? Now itwas Punnett’s turn to be puzzled,due to his inaccurate reading ofsome comments published by Yule.Why did Yule think that Punnettthought that the population shouldincreasingly be brown-eyed and bra-chydactylous? After all, whetherbrown eyes or short fingers wereincreasing or not, their inheritancepattern was clearly Mendelian!By this time, the relationship

among variation, heredity, breeding,selection, and evolution had beenmixed into a heady brew of concep-tual confusion of heroic proportions.Four people, Yule, Castle, Pearson,and Punnett (Fig. 2) had independ-ently seen what the problem was, buteach had solved only part of it. Butwhat has all this to do with Hardyand Weinberg, whoever they were?

HARDY, WEINBERG, AND THEIRSILENT PARTNERS

Punnett was confused, but smartenough to know that he wasn’t smartenough to solve the questions: How

Figure 1. Some defining wisdom from Samuel Johnson’s Preface, 1755.1

CROTCHETS & QUIDDITIES Antedating Ourselves 205

does Mendelian inheritance affectthe course of evolution? What wouldhappen in a population that did nothave equal allele frequencies? Hesought help from his Cambridgefriend and cricket partner, the fa-mous mathematician G. H. Hardy.In a terse but coyly worded letter

to Science, Hardy pointed out that ifparents are chosen at random so thatall types are represented in their pro-portions in the population, ratherthan by selectively breeding only cer-tain parental combinations, then inthe very next generation the popula-tion will attain stable genotype pro-portions, no matter what the startingfrequency. Here’s how to see thiseasily. In a given mating betweentwo parent types, one only has todeal with the specific offspring theycan produce. Since Mendel’s law saysthat each parent has a probabilityof 1/2 of transmitting either of itstwo alleles, the offspring proportionsare simple to work out, as we sawearlier with Mendel’s 3:1 in Aa 3 Aamatings.In offspring produced by a popula-

tion of parents, the probabilities arenot 1/2, but depend on the allele fre-quencies; that is, their proportions inthe population. If parents are matingat random, these proportions are theprobabilities that an allele in a ran-domly sampled offspring is of thattype. If a gene has two alleles, withproportions p and q in the popula-tion, the probability that the off-spring will be an AA homozygote isthe probability of drawing an A andthen doing it again: p � p ¼ p2; the

probability it’s aa is q2. An Aa hetero-zygote is produced by drawing an Athe first time, then a, or vice versa:pq þ qp equals 2pq. These are thefamous HW proportions, the baneof medical-school aspirants. Ratherthan thinking of drawing randompairs of alleles from a parental genepool, you can achieve the same resultby enumerating the offspring of allpossible matings, AA 3 AA, Aa 3 aa,and so forth, in their respective pro-portions in the population. (We usu-ally don’t make students do that.)The HW genotype proportions holdwhether or not there’s any domi-nance, but if there is, in the classicAa 3 Aa mating, p ¼ 1/2, and you getMendel’s 3:1 trait ratio.

The German physician and self-taught geneticist Wilhelm Weinbergwas searching for a human Mende-lian factor to study. His clinicalobservations suggested that Mendel’sprinciples might apply to humans aswell as peas, and he thought dizy-gotic twinning might be a likely can-didate. Weinberg worked out the te-dious algebra for all possible matingsof parents who might produce twins,implicitly assuming random mating.He found that the proportion of thegenotypes would stabilize after thefirst generation, making it possible topredict the frequency of twins amonga given offspring cohort. To his satis-faction, twin phenotypes did behaveas a Mendelian recessive. Perhapsbecause he wrote in German, usedwhat were for most biologists so-phisticated mathematics, and hadseverely criticized Pearson’s biomet-

rics, Weinberg was summarily ig-nored. Although his paper precededHardy’s 1908 paper by about sixweeks, he was not appreciated until1943. But, in many ways, it was hewho laid the foundations of modernpopulation genetics.The HW principle resolved a host

of conundrums. It showed how vari-ation, heredity, mutation, naturalselection, selective breeding, randommating, and Mendelian ratios are dif-ferent but related aspects of the evo-lutionary process. The 3:1 trait ratioplayed a major role in the history ofthis understanding. It has no specialstatus in nature, but it can seem to ifMendelian experimental crosses aremistaken for natural populations. AsCastle had realized, any allele fre-quency generates stable genotypeproportions once breeders stop selec-tive favoring of a given genotype andallow random mating.Mendelian heredity by itself does

not change the frequency of varia-tion and has no direct effect on evo-lution. Dominant alleles are not nec-essarily dominating in fitness. Natureis free to choose. But the stable HWproportions, called Hardy-Weinbergequilibrium, were seen as an ideal-ized baseline against which to evalu-ate the effect of the Four Forcemenof the Evolutionary Apocalypse: muta-tion, selection, migration, and chance(genetic drift). Since each of thesechanges allele frequencies, the searchfor HW proportions became a verita-ble growth industry in the 1960s and1970s as anthropologists collected bi-ological samples from indigenous

Figure 2. Hardy, Weinberg, and Castle equilibrate. About Hardy’s picture, it was said that anyone sitting like that had to have beeneducated at a public school.9 A. Hardy, B. Weinberg, C. Castle (Sources: Master and Fellows of Trinity College, Cambridge; Weinberg10;Castle, Jackson National Laboratory.) D. Pearson with the 87-year old Galton (www.galton.org).

206 Weiss and Kurland CROTCHETS & QUIDDITIES

people and estimated allele frequen-cies for the MN, ABO, and manyother genes. But this is generallyivory tower pedagogy because, ironi-cally, HW is not very useful forstudying evolution out there where itreally happens.

POPULATIONS EVOLVING . . .OR NOT

Ironically, though HW is held toreflect nonevolution, and HW pro-portions are usually found in nature,evolution does happen. That seemslike a contradiction until we lookclosely. First, every population is fi-nite, which means that allele fre-quencies essentially always change.For example, the parents of a popu-lation of 55 individuals with allelefrequency of 0.5 would be expectedto produce 1/4 AAs, but there can’tactually be 13.75 people, even ifeverybody is mating at random. Theoffspring frequency will not beexactly 0.5. There are many otherways by which purely chance aspectsof life and death change allele fre-quencies. This is genetic drift. EvenMendel knew you had to do manysubstantial experiments to reveal thetheoretical proportions, which arenever found exactly. Unlike con-trolled breeding, evolution is not arepeatable experiment. There’s nostarting over each generation, a factHardy recognized.11 Even tiny differ-ences add up over millions of years.Mutation changes allele frequen-

cies, but is so rare that we canhardly ever collect samples largeenough to detect its effect on HWproportions. Migration brings newvariation into a population. But untilrecently, that’s mainly been by mateexchange among nearby villages,which tend to be populated by closerelatives with similar allele frequen-cies, so migration is usually justanother aspect of genetic drift.But at least there is natural selec-

tion, no? Usually, no! As Darwinstressed, and most research hasshown, natural selection is generallyvery slow. Consequently, most selec-tive differences among genotypes areso small that it has proven very diffi-cult to detect selection by deviation

from HW proportions. Most of theexceptions are of very fast and strongselection, like pesticide resistance.Also, confusion of definition betweenstrong, intentional experimental se-lection and weak, blind natural selec-tion played a role in our HW history.Authors might know what they havein mind, but illustrating that by briefquotes could confuse a lexicographerlike Johnson. But as a rule, drift is amuch greater factor that obscuresmost of the direct evidence of selec-tion in nature.

What this means is that the FourForcemen of Evolution may be ridingall the time, but deviation from HWis not a good way to find them. Deca-des of testing in real human popula-tions have shown that most loci arein HW. Actually, things are rarely inexact HW. What we really meanwhen we say a population or sampleis ‘‘in HW’’ is that genotype propor-tions differ from HW by so little that,based on standard statistical signifi-cance criteria the deviations aren’t bigenough for us to allege that anythingnonrandom is going on, even if it is.

Convenient as they are as a base-line for teaching how evolutionworks, in fact HW proportions arenot even necessary for the forces ofevolution to occur! Nonrandom mat-ing, such as assortative mating inwhich like mates with like, can leadto deviations from HW (more homo-zygotes). But selection, mutation,migration, and drift still occur. HWaffects the relative frequency withwhich a given trait is presented tonature for screening to occur, but isnot required for that screening. Yeteven if, in practice, HW is an elusivebaseline for detecting evolution, it isnevertheless very useful in manyother ways that are not as wellknown.

DESPITE EVERY WAKINGMOMENT’S OBSESSION

Students not too tied up in its alge-bra should ask why HW proportionsare so widely found in nature. Afterall, students complain about thealgebra mainly because it keeps themfrom what really occupies their everywaking moment: choosing who to

mate with. Only a few wouldacknowledge that they mate at ran-dom, or at least try to. Since, behav-iorally, mating is anything but ran-dom, HW proportions seem paradox-ical. The key is random mating withrespect to what? The traits thatdetermine mate choice involve only atiny fraction of an individual’s genes.The rest are effectively combining atrandom. This may change, of course,when DNA-testing chips make it pos-sible to check out your date’s entiregenome.If an allele affects one’s risk of a

chronic disease, then genotypes con-taining that allele may die off fasterwith age than other genotypes. Thisis the case with Alzheimer’s diseaseand the gene called APOE. Carriersof the e4 allele at this gene preferen-tially die at younger ages, so the ge-notype frequencies change noticeablyas a cohort gets older. This is evi-dence of survival selection againstthe gene’s effects. But since theeffects are postreproductive, the re-sulting deviation from HW with agemay have nothing to do with evolu-tionary selection.If genes affect a disease risk, such

as of deafness or diabetes, personswith the disease socialize and maybe more likely to marry. That isassortative mating and can lead to adeviation from HW proportions atthe responsible genes, which can beimportant in studies designed to iden-tify those genes, because the statisti-cal methods typically assume HW.Methods for inferring peoples’

ancestry or for identifying genesassociated with disease can be sub-stantially affected if the populationhas social structure related to genes,as might occur with ethnic subdivi-sion among people with different his-torical ancestry. Population structureintroduces deviations from HW pro-portions in an overall sample, even ifthere is random mating within eachsubdivision. The result, called theWahlund effect, is an apparent excessof homozygotes compared to whatwould be expected from the overallallele frequency in the population.This deviation can lead to false iden-tification of genes that, in fact, havenothing to do with a trait understudy, so it is important to test for it.

CROTCHETS & QUIDDITIES Antedating Ourselves 207

HW applies to association amongalleles at different genes, as well asthose at the same gene. When genesare located close together on thesame chromosome, nonrandom asso-ciation among their alleles, calledlinkage disequilibrium, can be a use-ful indicator of a history of naturalselection affecting that chromosomeregion. For a given gene, randommating generates HW within a singlegeneration due to the Mendelianprinciple called segregation. But al-leles at different genes along a chro-mosome become associated due totheir shared history, which can re-flect hundreds of generations, evenwhen there is random mating,because the alleles do not follow theMendelian principle called independ-ent assortment except by the processof recombination. Linkage disequili-brium is a potentially strong, if indi-rect, indicator of recent natural se-lection, because favoring one spot ona chromosome for functional reasonsalso favors the nearby genes by‘‘hitchhiking.’’ This is a powerful toolfor gene mapping, where we can useknown polymorphic sites on a chro-mosome to help find unsuspectednearby sites causally associated witha trait we’re interested in.One of the most important sources

of deviation from HW proportionshas nothing to do with the peoplebeing studied. It has to do with labo-ratory error and takes advantage ofthe fact that, for most genes, humanpopulations do not significantly devi-ate from HW. When a genotype isdetermined, the chemical reaction(DNA sequence) has to detect bothalleles with equal effectiveness. Inheterozygotes, that means both reac-tions have to work. For example, if Areaction fails, an Aa person willappear to be an aa genotype. So astandard test in genetic studies is tolook for HW, regardless of anythoughts we may have about matingpattern.

ANTEDATING OURSELVES

Reading beyond narrow technicalconfines has become something of alost art. But it’s a confining loss thatleaves us vulnerable to semantic orcultural traps. For example, eventoday students routinely slip intothinking that alleles in nature haveequal frequency. Why? Because ofthe sometimes reflexive confusion ofMendelian breeding experiments andevolution: Aa 3 Aa matings haveclassical 3:1 offspring ratios thatillustrate dominance, while matingslike AA 3 aa are less pedagogicallyuseful because they only produce onekind of offspring. In fact, most alleles,at most genes, in most populations,have frequencies far from 1/2.

The search for general properties

of inheritance and their relation to

evolution was pursued largely in the

dark, or in selected corners of light.

Darwin knew of traits that ‘‘refused

to blend,’’ and Mendel intentionally

avoided traits that did. Darwin knew

that some traits showed ‘‘prepotency’’

(dominance) of one state over

another in hybrids.15 He was aware

of many of the aspects of segregation

that Mendel formally quantified. Dar-

win had materials in his library that

scantily referred to Mendel’s findings

(but not a copy of Mendel’s actual

paper), yet either didn’t know it or

ignored them.16 Groping in the dark

for an explanation of inheritance,

those were not the dots he con-

nected.Mendel was a brilliant inductive

experimentalist and deductive theo-retician.5 He ignored inconvenienttraits, focusing on traits that bredtrue to find a theoretical basis forusing hybridization to improve horti-cultural stocks. He experimentedwith equal frequency of the factors(alleles) in which he was interested,and in a cross there are only two. Hewould have had a hard time drawinghis conclusions had he tried to work

with wild peas in natural propor-tions, with many alleles of varyingfrequencies, while Darwin extrapo-lated from breeding to understandevolution in the wild, where he feltthe important traits were continuous,not discrete.Samuel Johnson illustrated the

meaning of the word ‘‘antedate’’ withthis quote: ‘By reading, a man does,as it were, antedate his life, andmakes himself contemporary withthe ages past’’1 (Fig. 3). Intellectualhistory is not valuable just for histor-ians or old fogies nostalgic for sim-pler days. To antedate ourselves andbecome contemporaries with ourpredecessors is to see what they saidand why. They were as intelligent aswe are, and had good reasons forwhat they said.The formal basis of evolutionary

theory is often explained in relationto HW proportions. The point offorce-marching students through it isso they can understand why nothinghappens when nothing happens. Weless often point out that in studyingevolution in the real world, wheresomething always happens, we strug-gle to determine which of the manypossible ways to generate small dif-ferences from ideal expectations isactually responsible for evolution.HW is useful in other importantways, not least being its historic roleen route to understanding the subtleconnection between inheritance andevolution. It is a simple principlethat turned out not to be so simpleafter all.

NOTES

We welcome comments on thiscolumn: kenweiss@psu.edu. There isa feedback and supplemental mate-rial page at http://www.anthro.psu.edu/weiss lab/index.html. We thankAnne Buchanan, Heather Lawson,and John Fleagle for critically read-ing this manuscript.

REFERENCES

1 Johnson S. 1755. Dictionary of the Englishlanguage. London: Strahan & Others.

2 Hitchings H. 2006. Defining the world: Theextraordinary story of Johnson’s dictionary.New York: Picador.

3 Boswell J. 1791. The life of Samuel Johnson,LL.D: comprehending an account of his studies

Figure 3. Johnson defines ‘‘antedate’’ by quoting from an essay by his contemporaryJeremy Collier.

208 Weiss and Kurland CROTCHETS & QUIDDITIES

and numerous works . . . In two volumes. Lon-don: printed by Henry Baldwin, for Charles Dilly.

4 Corcos AG, Monaghan FV, editors. 1993. Gre-gor Mendel’s experiments on plant hybrids: aguided study. New Brunswick, NJ: Rutgers Uni-versity Press.

5 Orel V. 1996. Gregor Mendel: the first geneti-cist. Oxford: Oxford University Press.

6 Weiss KM. 2002. Goings on in Mendel’s gar-den. Evol Anthropol 11:40–44.

7 Gerstein MB, Bruce C, Rozowsky JS, ZhengD, Du J, Korbel JO, Emanuelsson O, Zhang ZD,Weissman S, Snyder M. 2007. What is a gene,post-ENCODE? History and updated definition.Genome Res 17:669–681.

8 Sturtevant AH. 1965. A history of genetics.New York: Harper and Row.9 Kanigel R. 1991. The man who knew infinity:a life of the genius Ramanujan. New York:Washington Square Press.

10 Stern C. 1962. Wilhelm Weinberg. Genetics47:1–5.

11 Hardy GH. 1908. Mendelian Proportions ina mixed population. Science 28:49–50.

12 Weinberg W. 1908. Uber den Nachweis derVererbung beim Menschen. Jahreshefte desVereins fur vaterlandische Naturkunde in Wurt-temberg 64:368–382.

13 Boyer SH, editor. 1963. Papers on humangenetics. Englewood Cliffs: Prentice-Hall.

14 Castle WE. 1903. The laws of Galton andMendel and some laws governing race improve-ment by selection. Proc Am Acad Sci 35:233–242.

15 Darwin C. 1900. The variation of animals andplants under domestication (orig. pub. 1868).New York: D. Appleton.

16 Sclater A. 2003. The exent of Charles Dar-win’s knowledge of Mendel. Georgia J Sci61:134–137.

VVC 2007 Wiley-Liss, Inc.

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CROTCHETS & QUIDDITIES Antedating Ourselves 209