Fossil primates 1

Fossil primatesExtinct members of the order of mammals to whichhumans belong. All current classifications divide theliving primates into two major groups (suborders),but zoologists differ as to whether the tarsier (Tar-sius) should be classified with the lower primates(lemurs, lorises, and bushbabies) or the higher pri-mates (New and Old World monkeys, greater andlesser apes, and humans).

All primates have a common origin which, how-ever, is not reflected in the universal possession ofa suite of diagnostic features. The order as a wholehas been characterized in terms of showing a groupof progressive evolutionary trends, notably towardthe predominance of the visual sense, the reductionof the sense of smell and associated structures, im-proved grasping and manipulative capacities, and en-largement of the higher centers of the brain. Amongthe extant primates, the lower primates more closelyresemble forms that evolved relatively early in thehistory of the order, while the higher primates rep-resent a group more recently evolved (Fig. 1). Aclassification of the primates, as accepted here, is asfollows:

PrimatesSemiorder Plesiadapiformes (archaic extinct

primates)Superfamily Paromomyoidea (paro-

momyids, picrodontids)Superfamily Plesiadapoidea (plesia-

dapids, carpolestids)Semiorder Euprimates (modern primates)

Suborder Strepsirhini (toothcombed “prosimi-ans” and extinct allies)

Infraorder Adapiformes (extinct earlystrepsirhines)

Superfamily Adapoidea (extinct earlystrepsirhines)

Infraorder Lemuriformes (modernstrepsirhines)

Superfamily Lemuroidea (typicallemurs)

Superfamily Indrioidea (indris,aye-ayes, and subfossil relatives)

Superfamily Lorisoidea (lorises,bushbabies, mouse and dwarflemurs)

Suborder Haplorhini (tarsiers and higherprimates)

Hyporder Tarsiiformes (tarsiers and extinctrelatives)

Superfamily Tarsioidea (tarsiers andclose relatives)

Superfamily Omomyoidea (extinctearly haplorhines)

Hyporder Anthropoidea (higher primates)Infraorder Paracatarrhini (archaic anthro-

poids)Family Oligopithecidae (archaic

protoanthropoids)

Family Parapithecidae (extinctOligocene monkeys)

Infraorder Platyrrhini (New World anthro-poids)

Superfamily Ateloidea (New Worldmonkeys)Family Atelidae (howler, spider,

saki, titi, and owl monkeys)Family Cebidae (squirrel, capuchin,

and marmoset monkeys)Infraorder Catarrhini (Old World anthro-

poids)Parvorder Eocatarrhini (archaic

catarrhines)Family Propliopithecidae (extinct

common ancestors of hominoidsand cercopithecoids)

Family Pliopithecidae (extinct earlycatarrhines)

Parvorder Eucatarrhini (advanced catar-rhines)

Superfamily Hominoidea (apes andhumans)Family Proconsulidae (extinct early

apes)Family Hylobatidae (gibbons, lesser

apes)Family Hominidae (great apes,

humans, and extinct relatives)Superfamily Cercopithecoidea (Old

World monkeys)Family Cercopithecidae (Old World

monkeys)

Early primates. The earliest primates are placed intheir own suborder, Plesiadapiformes, because theyhave no direct evolutionary links with, and bearno adaptive resemblances to, any group of livingprimates. However, the chewing teeth and thelocomotor anatomy of these fossil forms sufficientlyresemble those of later primates to demonstratethe common origin of the two groups. Best knownfrom the Paleocene Epoch, around 66–54 millionyears ago (Ma), and found in both the Old Worldand the New World, the plesiadapiforms retainedclawed hands and feet, had rather small brainscompared to their body size, possessed large special-ized front teeth, and were probably arboreal in habit(Fig. 2). These animals are also known from fossildeposits on Ellesmere Island, in Arctic Canada, whichwas then covered by the subtropical forest stretchingcontinuously from western North America across alandlocked North Atlantic into western Europe.

Eocene primates. There is no known plesiadapi-form that is a satisfactory candidate for the ances-try of the fossil primates of modern aspect typicalof the succeeding epoch, the Eocene (54–34 Ma).Often termed euprimates, they are divided broadlyinto lemurlike forms, usually grouped into thesuperfamily Adapoidea, and tarsierlike forms(Omomyoidea), although this division may prove tobe oversimplified. Eocene primates of both the Old

2 Fossil primates

STREPSIRHINI TARSIIFORMES

Lemuridae Indriidae Daubentoniidae Lorisidae Tarsiidae

HominidaeHylobatidaeCercopithecidaeAtelidaeCebidae

ANTHROPOIDEA

Fig. 1. Representatives of living primate families.

and New Worlds already display the trends that markmodern primates as a whole: These arboreal animalspossessed grasping hands and feet in which sharpclaws were replaced by flat nails backing sensitivepads; the snout was reduced, suggesting a deempha-sis of smell, while the bone-ringed eyes faced moreforward, producing stereoscopic vision and suggest-ing primary reliance on the sense of sight; and thebrain was somewhat enlarged relative to body sizewhen compared to those of other mammals of theperiod.

10 cm

Fig. 2. Reconstructed skeleton of Plesiadapis tricuspidens, a Eurasian plesiadapiform from about 60 Ma. Known parts areshaded.

It is possible that the origins of some specificgroups of extant lower primates may be traced backto or through certain known primate genera of theEocene. Even if this is not the case, however, it isuniversally accepted that the antecedents of theseliving forms are to be sought somewhere within theEocene primate radiation, though the details of thisancestry may remain unclear. In North America andEurope, lower primates had nearly disappeared bythe close of the Eocene, while virtually all knownfossil lower primates of later epochs in Africa and

Fossil primates 3

Asia are closely related to modern primates of theseareas.

Modern lower primates. The extant lower primatesare allocated to the suborder Prosimii if Tarsius is in-cluded, and to the suborder Strepsirhini if this strangeprimate is excluded, as is provisionally done here. Allextant strepsirhines possess dental scrapers (tooth-combs), in which the lower front teeth are elon-gated, closely approximated, and forwardly project-ing. These specialized structures are used both infeeding and in social grooming. Additionally, all livingstrepsirhines retain a moist, naked rhinarium (wetnose, as in a dog) and related structures, reflecting agreater reliance on the sense of smell than is typicalof higher primates. All are also united by possessinga toilet claw (used for self-cleaning) on the seconddigit of the foot. Although all strepsirhines possessgrasping hands and feet, their manual dexterity isgenerally inferior to that of higher primates; theirbrains are also relatively small.

There is no ancient primate fossil record in Mada-gascar, home of the most diverse group of modernlower primates, but extinct species little more thana thousand years old document a much wider adap-tive radiation before the arrival of humans on theisland. Notable among those extinct lemurs arePaleopropithecus, a large-bodied climber-hangersomewhat like the orangutan in its locomotion(Fig. 3); the semiterrestrial and dentally specializedmembers of the subfamily Archaeolemurinae, relatedto the living indriids but adapted somewhat like ba-boons; and Megaladapis, a very large, verticallypostured, short-limbed, and probably slow-movingclimber with adaptive resemblances to the koalaof Australia. Fragmentary remains of lorisoid strep-sirhines are known from the Miocene of East Africaand Pakistan.

Tarsiers. The tiny Tarsius, which lives today inSoutheast Asia, represents a link between the tooth-combed strepsirhines and the anthropoids (mon-keys, apes, and humans). In many respects (such aslack of toothcomb, dry nasal area, molecular biology,and placentation), it is related to the anthropoids,but dentally it is usually thought primitive, althoughsome authors have found similarities to some strep-sirhines. The extinct Eocene omomyoids are close totarsiers skeletally; they are often considered broadlyancestral to the anthropoids for that reason and alsobecause some have monkeylike front teeth. A tarsier-like fossil has been recovered in Egypt from depositsof early Oligocene age (35 Ma). Living tarsiers eat in-sects and small vertebrates, and are vertical clingersand leapers; their nocturnal habit is shown by theirrelatively huge eyes. They appear to live mainly inpairs, but they may form larger associations in someregions.

Higher primates. The anthropoids include threemain groups of living animals and their extinct rel-atives; their divergence from a possibly omomyoidstock probably took place some 50 Ma. The monkeysof the New World and those of the Old are of sim-ilar evolutionary grade, but the latter share a much

20 cm

Fig. 3. Anjohibe specimen of Paleopropithecus ingens, mounted in probable habitatposture. (Photo courtesy of American Geological Institute)

more recent common ancestry with apes and hu-mans, with which they are grouped in the infraorderCatarrhini.

The earliest known anthropoids may be repre-sented by a few teeth (of Algeripithecus) fromAlgeria about 45 million years old, but better-preserved forms appear in the Fayum region of Egyptbetween 35 and 33 Ma. Although now a desert, at thetime this was a lush tropical forest through whichmeandered the sluggish proto-Nile river. Three maingroups of early higher primates are represented: theoligopithecids, the parapithecids, and the proplio-pithecids. The former two appear to be only distantlyrelated to any of the living monkeys or apes, althoughthey may be termed monkeys in the broad sense, astheir adaptations are similar to those of modern mon-keys. The propliopithecids (species of Propliopithe-cus, including Aegyptopithecus) may be close to thecommon ancestry of later catarrhines (Old World an-thropoids). These arboreal animals were the size ofsmall cats, with apelike teeth, small brain, and limbssimilar to those of the acrobatic South Americanatelines. Representatives of modern lineages begin tooccur in the fossil record by about 28–20 Ma in bothhemispheres. Most scholars subscribe to a coloniza-tion of South America by Fayum-age African anthro-poids that crossed a then-narrower South Atlanticocean on rafts of natural vegetation to reach the iso-lated island continent.

New World primates. The platyrrhine or ateloidmonkeys of South and Central America are dividedinto two families, of which the contents vary accord-ing to author. All living (and well-known extinct)forms are arboreal and occupy forested areas be-tween Argentina and southern Mexico. A distinctive

4 Fossil primates

evolutionary pattern observed in this group is the an-tiquity of the extant lineages as reflected by the closerelationships of most of the few known fossils tomodern genera. The small marmosets and the com-mon squirrel and capuchin monkeys are groupedinto the family Cebidae, while the generally large-bodied spider-howler and saki-uakari groups arelinked to the smaller titis and (probably) owl mon-keys in the Atelidae. These two families differ in therelative robustness of their jaws and reduction of lastmolars.

The earliest fossil platyrrhine, 26-million-year-oldBranisella from Bolivia, is as yet known only byteeth and jaw fragments. A probable size reductionof its last molars may suggest an evolutionary rela-tionship to the Cebidae. It has also been suggestedthat Branisella might have lived in a savannahlikeenvironment and been adapted to life at least partlyon the ground, as opposed to all later platyrrhines.Two slightly later (about 20 Ma) species from Patag-onia and Chile are also probable cebids, close to theancestry of the living Saimiri, and several forms of18–17 Ma represent early atelids, close to the liv-ing pitheciines (the saki-uakari and titi-owl monkeygroups).

The largest number of fossil platyrrhines comesfrom the La Venta beds of Colombia, dated about13 Ma. These include one or two species in eachsubfamily of Cebidae (Callitrichinae and Cebinae),one relative each of owl and howler monkeys, andfour early members of the saki-uakari group. Thelast 100,000 years saw another flowering of extinctplatyrrhine lineages. A cave site in eastern Brazil hasyielded partial skeletons of “giant” relatives of thehowler and spider monkeys, while several localities

~10 cm

Fig. 4. Reconstructed skeleton of Mesopithecus pentelicus, an 11- to 8-million-year-old colobine monkey. Known parts areshaded. (After A. Gaudry, Animaux Fossiles et Geologie de l’Attique, Savy, Paris, 1862)

in the Caribbean produced controversial fossils per-haps related to howlers, saki-uakaris, and squirrelmonkeys (or possibly representing a distinct lineagewhose members came to resemble those othergroups). See MONKEY.

Old World monkeys. The living Cercopithecidae aredivided into two subfamilies, Colobinae and Cerco-pithecinae. The oldest cercopithecids are found inAfrica, with a few fossil forms such as Victoriapithe-cus of 20–15 Ma probably predating the divergenceof the modern subfamilies. The cercopithecines in-clude a wide variety of forms, all of which sharecheek pouches for temporary food storage and usu-ally large incisors reflecting a fruit diet; colobines, bycontrast, are more restricted in morphology, range,and behavior pattern, and all are leaf eaters witha complicated digestive tract to facilitate the low-nutrition diet. All cercopithecids possess ischial cal-losities, or rump sitting pads, which have been lostto a greater or lesser extent in apes and humans.

The earliest members of the two living subfamiliesalso are mainly African. One colobine jaw is knownby 9 Ma, and from 7 to 5 Ma species of both cerco-pithecines and colobines become more abundant.Large collections of Old World monkey fossils havebeen recovered from East and South African sites(often in association with early human remains) inthe 4–1.5 Ma interval. Cercopithecines are repre-sented first by Parapapio, which was a semiterres-trial animal probably closer to the common ancestorof later forms, and then by several species of thehighly terrestrial living Theropithecus. At least threetypes of large colobine monkeys were also common,ranging from arboreal to terrestrial in adaptation.Many of these species were significantly larger than

Fossil primates 5

their living relatives: The biggest colobine may haveweighed close to 50 kg (110 lb), while a Theropithe-cus dated about 1 Ma has been estimated nearly twicethat large. Some of these large and slow-movingspecies may have been hunted and perhaps drivento extinction by early humans.

Cercopithecids entered Eurasia from Africa. Meso-pithecus pentelicus, an 11- to 8-million-year-old colo-bine known in a geographical range from Germanythrough Afghanistan, is the best-represented Eurasianfossil monkey, with dozens of individuals recoveredfrom sites in Greece (Fig. 4). It was semiterrestrial,perhaps like the living hanuman langur Semnopithe-cus entellus, sleeping in trees and feeding on theground along watercourses. A possible descendant isDolichopithecus, which lived in Europe from about4.5 to 2.5 Ma and perhaps in Mongolia and Siberia aswell. It was even more terrestrially adapted, moreso than any living colobine. The living macaques(Macaca) are widespread across eastern Asia and inNorth Africa, and their fossil record adds to that largerange. Scattered specimens are known from NorthAfrica after 7 Ma, and populations have been recov-ered across Europe from 5.5 Ma to about 100,000years ago. A large and highly terrestrial relative,Paradolichopithecus, inhabited Europe, central Asia,and perhaps eastern Asia from about 3 to 1.5 Ma.

Hominoids. The most humanlike of all primates arethe apes, which form a group distinguished bygenerally large body size, relatively large brain, lackof an external tail, and advanced placentation pat-tern. Living forms include the lesser apes, or gibbons(Hylobates), placed in their own family Hylobatidae,and the several great apes: orangutan (Pongo), chim-panzee (Pan), and gorilla (Gorilla). The great apesand humans, along with some extinct relatives, aregrouped as the Hominidae by some authors, whileothers place only humans in the Hominidae and classall great apes in the Pongidae.

One of the earliest probable members of Homi-noidea is Proconsul, of the East African Miocene,23–14 million years old; a few teeth of a similar formdate to 26 Ma. Proconsul is well known by most ofits skeleton (Fig. 5). Several species ranged in sizefrom small chimpanzee to small gorilla, with a some-what chimplike skull, large projecting canine teeth,and limb bones seemingly adapted to quadrupedalrunning. However, Proconsul has few of the defin-ing features of the ape group. It lacks the mobileshoulder characteristic of all living species, and thereis some controversy over its tail: some workers be-lieve that tail bones have been found but not alwaysrecognized as such. For the present, Proconsul isretained as a hominoid belonging to a distinct ar-chaic family of its own. Two other groups of roughlycontemporaneous species (the Eurasian Pliopitheci-dae and the African “Dendropithecus-group”) areclearly more “primitive” than Proconsul, althoughthey have at times wrongly been included in Homi-noidea, usually as purported relatives of the gibbons.The oldest fossil gibbons date only to about 1 Ma; pre-sumably, their ancestors lived after Proconsul and

entered Eurasia about the same times as did earlyHominidae.

Several fossil apes from Africa dating to 20–14 Maare often placed in the Hominidae because they ap-pear to share “advanced” dental features with themodern great apes. But most of these species haverecently been questioned as hominids because theylack apelike features of the postcranial skeleton (inthe elbow, shoulder, hip, and knee joints, especially).Surprisingly, the oldest of these, Morotopithecus,may be the most “modern,” although only fragmen-tary postcranial elements are known. The youngest,Kenyapithecus, is similar to the first Eurasian homi-noid, Griphopithecus, found in Turkey, Germany,Slovakia, and Austria between 16 and 13 Ma. None ofthese fossils are specially related to any living greatape, and they are often placed in the hominid sub-family Kenyapithecinae or even outside Hominidae.

Although interpretations vary, there appear to bethree groups of Eurasian hominids between 13 and7 Ma. Dryopithecus is characteristic of the Dryo-pithecinae, which may include the common ances-tors of all later great apes (and humans). This animalhas been known since the 1850s, but only in the1990s were partial crania and skeletons described.These show several similarities to living apes in gen-eral but not to any specific forms.

Spread of modern ape ancestors. Most scientiststoday agree that, of the great apes, the orangutanis evolutionarily farthest from humans. This view is

~10 cm

Fig. 5. Reconstructed skeleton of Proconsul africanus, an early hominoid (23–14 Ma) fromEast Africa. Known parts are shaded. (After R. L. Ciochon and R. S. Corruccini, eds., NewInterpretations of Ape and Human Evolution, Plenum Press, 1983)

6 Fossil primates

based mainly on the results of numerous studies ofproteins and DNA sequences, which reveal great sim-ilarity among the genes of gorillas, chimpanzees, andhumans; and with orangutans, gibbons, and monkeyssuccessively farther from that close-knit group. As aresult, orangutans and their extinct relatives are hereplaced in the subfamily Ponginae, while African apes,humans, and their relatives are included in Homin-inae. The living orangutans (Pongo) inhabit a smallrange in the deep forests of Borneo and Sumatra; lessthan 1 Ma, the same species was also present as farnorth as southern China. See APES.

The orangutan lineage is, however, the oldest well-documented one among all catarrhines. Fossils fromPakistan and India known as Sivapithecus show fa-cial, palatal, and dental architectures clearly special-ized in the orang direction as far back as 13–12 Ma.Although slightly younger in time, Ankarapithecusfrom Turkey at approximately 10 Ma appears inter-mediate between Sivapithecus and Dryopithecus infacial morphology. These three genera seem to form atransformation series representing the approximatemanner in which orang ancestry evolved from dryop-ithecines, and both Ankarapithecus and Sivapithe-cus are usually included in Ponginae. But whereasthe living great apes (and human ancestors) share acomplex of arm-bone features related to suspensorybehavior and forelimb flexibility, the upper arm ofSivapithecus lacks at least one part of this complex.Thus, it is possible either that this lack denies Siva-pithecus close relationship with orangs or other apes,or that Asian and African great apes independentlyevolved these features long thought to documenttheir shared ancestry. However, the lack may merelyrepresent a secondary specialization of Sivapithecuswhich happens to be (convergently) similar to morearchiac apes like the kenyapithecines. This last op-tion makes sense, as Sivapithecus in other ways ap-pears to be somewhat more adapted to quadrupedallife on the ground than is the living orangutan.

Two larger species which probably belong to thePonginae are placed in the genus Gigantopithecus:One dates to about 9–6 Ma from India and Pakistan,the other lived about 1.5–0.5 Ma in China andperhaps Vietnam. Hundreds of specimens, mostlyisolated teeth, are known from China, and these doc-ument a species which was probably the largest pri-mate that ever lived (perhaps weighing 200–400 kgor 440–880 lb, although teeth are not the best bodypart from which to estimate weight). Gigantopithe-cus was once thought to be near the ancestry of hu-mans, but today it is usually considered a collateraldescendant of Sivapithecus.

The pongines probably evolved in Asia from anarboreal dryopithecine (or even kenyapithecine) an-cestry which expanded into less forested environ-ments. Such a habitat would have provided anabundance of gritty and tough food objects, towhich this group’s dentition appears adapted. It wasat first thought that these creatures might have spentsignificantly more time walking and feeding on theground than modern or earlier apes, but partial limb

bones suggest overall similarity of structure, and thusprobably of behavioral function, to living arborealand partly ground-living apes. They share withorangutans and some early humans a complex ofdental-related features, including a thick molarenamel covering (to prolong tooth life with heavywear), large molars in relation to estimated body size,strongly buttressed jaws (to take up stresses of heavychewing), and some reorientation of the front teeth.A major factor in human dental evolution was facialshortening combined with reduction of the canineteeth and their transformation into incisorlike ele-ments, but no Miocene fossils yet known show thisfeature clearly.

The origin of the Homininae is more problem-atic. The fossil ape Graecopithecus (also termedOuranopithecus) is known from several Greek local-ities estimated to date between 10 and 8 Ma. Well-preserved facial material of this animal and of Dryo-pithecus recovered or reanalyzed in the 1990s has leddifferent workers to suggest that one or both formsmay lie near the split between Ponginae and Homin-inae or already on the hominine lineage, effectivelyclose to the common ancestor of African apes and hu-mans. This would agree well with the date of about13–12 Ma for the earliest pongines on the assumptionthat both branches of the split would have developedtheir derived features contemporaneously. Graeco-pithecus shows more evidence of the downwardlybent face typical of African apes (a pattern termedklinorhynchy) and also very thick molar enamel (asexpected in an early hominine), while Dryopithe-cus has thin enamel. Some of the differences be-tween them may just reflect the far larger size ofGraecopithecus, but at present this genus appearsmore derived in the direction of later hominines. Atabout the same time in Africa, the only known apefossil is a single upper jaw which was named Sambu-rupithecus in 1997 and which may also represent anearly, gorillalike member of Homininae. These fossilsimply that the hominines may have evolved in Eurasiaand then returned to Africa after about 10 Ma. Pre-vious workers often thought that the hominine lin-eage could be traced purely within Africa, but thathypothesis now appears less likely. The ancestry ofthe African apes is still a mystery, as no fossils haveyet been found which clearly represent their lineagebefore or after separation from humans.

Human evolution. After about 5 Ma, evidence forthe human clade is increasingly common. The nameArdipithecus ramidus has been given to a smallgroup of fossils dated about 4.4 Ma at the site ofAramis in the Awash Valley of Ethiopia. This speciesappears to be the most conservative (“primitive”)member of the Hominini, the lineage including livinghumans but postdating the last common ancestorsof humans and other apes. Ardipithecus ramidus ischaracterized by teeth which combine some apelikemorphology with reduced, incisiform canines, andalso by an anterior placement of the foramen mag-num (through which the spinal cord connects to thebrain) indicating that the head was balanced atop

Fossil primates 7

the trunk in the manner of bipedal humans ratherthan quadrupedal apes. A partial skeleton has beenrecovered, but not described as of early 2001.

Several species of the genus Australopithecus areknown from sites dating between 4.2 and 2.3 Main South Africa, Chad, and the Rift Valley fromTanzania through Ethiopia. They have crania withinternal volumes (“brain size”) of 400–500 ml, inthe range of living gorillas; body weight, however,is far smaller, about 30 kg for females, up to 60 kg formales. The jaw musculature was small enough notto require strong crests on the outer surface of theskull. The dentition had moderately large incisors,relatively small and partly incisivized canines, thick-enameled molars, and a broadly “humanlike” arcadeshape. The postcranial skeleton was clearly adaptedto upright bipedalism (also indicated by footprinttrails), although it differed in detail from mod-ern humans, with relatively short legs. The diet ofthese forms was probably omnivorous, includingfruits, seeds, and perhaps scavenged animal pro-tein; there is no evidence for toolmaking. See AUS-

TRALOPITHECINE.The “robust” australopiths, genus Paranthropus,

were generally younger (about 2.6–1.4 Ma) and morederived craniofacially. Their postcanine teeth weregreatly enlarged and adapted to crushing and grind-ing hard food items, while the canines and incisorswere strongly reduced except in the earliest species,P. aethiopicus. Sagittal and nuchal crests served asanchors for the large temporal musculature coveringa vault enclosing an only slightly larger brain than inAustralopithecus; the postcranial skeleton is poorlyknown, but body structure and size were probablynot much different from that of its predecessor.

The earliest toolmakers probably belonged tospecies included in the living genus Homo, first ap-pearing 2.5–2.2 Ma in Malawi, Kenya, and Ethiopia,soon after the oldest stone tools. There is some de-bate over the number of early Homo species, but itseems likely that at least three were contemporane-ous if not actual neighbors in eastern Africa around2 Ma. Soon afterward, Homo erectus (or accordingto some authors, a closely related species named H.ergaster) emigrated from Africa to eastern Eurasiawhere H. erectus persisted until at least 300 Ka(thousand years ago). Continental Europe may nothave been colonized until about 1 Ma; almost allyounger populations there appear to be part of alineage which led eventually to the Neanderthals,most common from 200 to 30 Ka between Spainand central Asia. African populations of the last halfmillion years evolved less directly into anatomicallymodern humans (Homo sapiens sapiens), some ofwhom dispersed via southwestern Asia to colonizethe rest of the Earth after 150 Ka. See FOSSIL HUMANS;MAMMALIA. Eric Delson; Ian Tattersall

Bibliography. D. R. Begun, C. V. Ward, and M. D.Rose (eds.), Miocene Hominoid Fossils: Functionaland Phylogenetic Implications, 1997; E. Delsonet al. (eds.), Encyclopedia of Human Evolution andPrehistory, 2d ed., 1999; J. G. Fleagle, Primate Adap-tation and Evolution, 2d ed., 1998; R. F. Kayet al. (eds.), Vertebrate Paleontology in the Neotrop-ics, 1997; R. F. Kay, C. Ross, and B. A. Williams, An-thropoid origins, Science, 275:789–804, 1996; C.-B.Stewart and T. Disotell, Primate evolution—in andout of Africa, Curr. Biol., 8:R582–R588, 1998; F. S.Szalay and E. Delson, Evolutionary History of thePrimates, 1979.

Reprinted from the McGraw-Hill Encyclopedia of

Science & Technology, 9th Edition. Copyright c© 2002 by

The McGraw-Hill Companies, Inc. All rights reserved.