Chapter 36

The Evolution and Distribution of Later Pleistocene Human Populations

Christopher B. Stringer

As the record of human fossils increases in geographical range and local detail, new opportunities will arise to study the biogeography of modern human origins. Paleo-climatic data are increasingly available for regions inhab-ited in the Pleistocene; and with the developmeat or wider application of new physical dating techniques, it should become more feasible to relate evolutionary events and dispersals to environmental changes. In this chapter, I discuss some of the outstanding problems and recent progress in looking at Neanderthal evolution from a biogeographic and adaptive perspective; I also examine data on modern human origins from this same perspec-tive.

Plio-Pleistocene Hominids

Homo erectus is generally regarded as the first member of the genus Homo to have dispersed beyond the confines of the probable hominid homeland of Africa; we should therefore expect to see in this species the emergence of patterns of thermoregulatory adaptation paralleling those which we find in Homo sapiens today. A brief dis-cussion of the origin and evolution of Homo erectus is perhaps appropriate before we consider the later Pleisto-cene record; for the purposes of this discussion I shall assume that specimens such as KNM-ER 3733 and WT

15000 represent Homo erectus (Rightmire, 1990) rather than Homo ergaster (Wood, 1992). It is usually assumed that Homo erectus originated from Homo habilis in the

Copyright © 1995 by Yale University. All rights reserved. ISBN 0-300-06348-2.

Late Pliocene of Africa. There are, however, factors that suggest caution concerning this assumption.

First, there are probably at least two species presently subsumed within the category of "Homo habilis," al-though there is no agreement as to how the individual specimens should be segregated (cf. Wood, 1992, with Stringer, 1986a, and Rightmire, 1993). Moreover, it is not at all clear which of the range of material presently allocated to Homo habilis might provide the most plausi-ble ancestral form for early American Homo erectus. Second, it is possible from occipital KNM-ER 2598 that Homo erectus was present contemporaneously with Koobi Fora specimens assigned to Homo habilis, such as KNM-ER 1470, 1802, and 1813 (Wood, 1992). This in turn casts doubt on the assumed link, based on postcranial similarities, between large examples of Home habilis sensu late and Homo erectus, because erectus-like postcranial bones might actually derive from Homo erectus rather than from Homo habilis sensu late. Third, there is possible evidence for a Late Pliocene presence of Homo erectus in Eurasia, depending on interpretations of specimens such as the Dmanisi mandible from Georgia (Gabunia and Vekua, 1995) and the revised dating of the earliest Homo erectus I "Meganthropus" fossils from Java (Swisher et al., 1994). This last point is linked with continuing claims for Eurasian artifacts of Late Pliocene age (Bonifay and Vandermeersch, 1991). From available fossil and geo-chronological evidence, it is still possible that Homo erectus originated outside of Africa, but clarification of this possibility will depend on further absolute dating of sites such as Dmanisi and Sangiran as well as on continu-ing reassessments of the African and non-African fossil evidence.

Chopler 36

The [volulion ond Distribution of Loter Pleistocene llumon Populotions

(hrislopher B. Stringer

As the record of human fossils increases in geographicalrange and local detail, new opportunities will arise tostudy the biogeography ofmodern human origins. Paleo-

climatic dataare increasingly available for regions inhab-ited in the Pleistocene; and with the development orwider application of new phjrsical dating techniques, itshould become more feasible to relate evolutionaryevents and dispersals to environmental changes. In thischapter, I discuss some of the outstanding problems andrecent progress in looking at Neanderthal evolution froma biogeographic and adaptive perspective; I also examinedata on modern human origins from this same pcrspec-tive.

Plio-Pleistocene Hominids

Homo erectus is generally regarded as the first member ofthe genus Hont to have dispersed beyond the confines ofthe probable hominid homeland of Africa; we shouldtherefore expect to see in this species the emergence ofpatterns of thermoregulatory adaptation parallelingthose which we find in Homo sapiens today. A brief dis-cussion of the origin and evolution of Homo erectus isperhaps appropriate before we consider the later Pleisto-cene record; for the purposes of this discussion I shallassume that specimens such as KNM-ER 3733 and wr15000 represent Homl erectus (Fiightmire, 1990) ratherthan Homo ergaster (Wood, 1992).It is usually assumedthat Homo erectus originated from Homo habilis in the

Copyright O 1995 b"v Yale University. AII rights reserved.ISBN 0-300-06348-2.

Late Pliocene of Africa. There are, however, factors thatsuggest caution concerning this assumption.

First, there are probably at least two species presentlysubsumed within the category of "Homo habilis," al-though there is no agreement as to how the individualspecimens should be segregated (cf. Wood, 1992, withStringer, 1986a, and Rightmire, 1993). Moreover, ir isnot at all clear which of the range of material presentlyallocated to Homo habilis might provide the most plausi-ble ancestral form for early American Honto erectus.

Second, it is possible from occipital rNna-tn 2598 thatHomo erectu.r was present contemporaneously withKoobi Fora specimens assigned to Homo habilis, such as

KNM-ER 1470,1802, and l8l3 (Wood, 1992). This in turncasts doubt on the assumed link, based on postcranialsimilarities, between large examples of 11o mo habilis sensu

lato and Homo erectus, because erectus-llke postcranialbones might actually derive from Hctmo erectus ratherthan from .I1o mo habilis sensu lato. Third, there is possible

evidence for a Late Pliocene presence of Homo erectus inEurasia, depending on interpretations of specimens suchas the Dmanisi mandible from Georgia (Gabunia andVekua, 1995) and the revised dating of the earliest Homoerectus / "Meganthropu.s"fossils fromJava (Swisher et al.,1994). This last point is linked with continuing claimsfor Eurasian artifacts ofLate Pliocene age (Bonifay andVandermeersch, 1991). From available fossil and geo-chronological evidence, it is still possible that Homoerectus originated outside of Africa, but clarification ofthis possibility will depend on furrher absolute dating ofsites such as Dmanisi and Sangiran as well as on continu-ing reassessments of the African and non-African fossilevidence.

The Evolution and Distribution of Later Pleistocene Human Populations 525

The Middle Pleistocene

By the middle part of the Middle Pleistocene, ca. 400 thousand years (kyr), Homo erectus was apparently still present in China and Indonesia (with the Javanese Ngan-dong hominids, which I assign to Homo erectus, being perhaps even younger; Bartstra et al., 1988). But there is also evidence at this time for additional, more derived hominids in Africa (e.g., Elandsfontein, Ndutu, Broken Hill, and perhaps Bodo), Europe (Mauer, Petralona, Ar-ago), and perhaps China (Yunxian) (fig. 36.1). Their pre-cise taxonomic status is still uncertain, but they show departures from the typical Homo erectus morphology in such features as the reduced cortical bone in ectocranial buttresses and the tympanic, and the shape of cranial bones such as the temporal, parietal, and occipital. Many of the latter features appear to be related to an overall increase in endocranial volume, which seems to become

accentuated during the course of the Middle Pleistocene. The face, when preserved, is intermediate in mean values measuring total projection between Homo erectus and those of later humans, and there is an increase in midfa-cial projection in several specimens, which is linked with greater nasal prominence. The postcranial skeleton is poorly known at present but retains features of Homo erectus, such as an external iliac buttress (Stringer, 1986b) and the relatively high levels of cortical thicken-ing and femoral-shaft width found in archaic Homo gen-erally (Ruff et al., 1993). There are, as yet, no data on body proportions to compare with the linear, heat-adapted physique inferred for the much earlier WT 15000 Homo erectus individual (Ruff, 1991).

In light of remarkable new finds from Atapuerca (Ar-suaga et al., 1993; Stringer, 1993a), the status of the European Middle Pleistocene sample is currently the subject of some discussion. Extensive cranial and post-

.

AGE(YEARS) AFRICA EURASIA EAST ASIA/AUSTRALIA

30,000

50,000

100,000

250,000

500,000

1,000,000

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ELANOSEDNTIEH, MOUTH

1000, SALE

BAR 11160

HGALORA

IRH000

0100VAI, TIGHENIF

OLDUVAI

A

DAAANISI

Fig. 36.1. Distribution of some important Pleistocene fossil hominids in time and space. My taxonomic preference is to call morph A Homo eredus; B Homo heidelbergensis or Homo rhodesiensis; C Homo neandertholensis, perhaps extending back to Arago or even Mauer (thus affecting the status of llama heidelbergensis); and D Homo sapiens.

The Evolulion ond Dhlribution of Loter pleistocene Humon populotions

The Middle Pleistocene

By the middle part of the Middle pleisrocene, ca. 400thousand years (kyr), Homo erectus was apparently stillpresent in China and Indonesia (with theJavanese Ngan_dong hominids, which I assign to Homo erectus, beingperhaps even younger; Bartstra et al., 1988). But there isalso evidence at this time for additional, more derivedhominids in Africa (e.g., Elandsfontein, Ndutu, BrokenHill, and perhaps Bodo), Europe (Mauer, petralona, Ar-ago), and perhaps China (Yunxian) (fig. 36.1). Their pre-cise taxonomic status is still uncertain, but they showdepartures from the typical Homo erectus morphology insuch features as the reduced cortical bone in ectocranialbuttresses and the tympanic, and the shape of cranialbones such as the temporal, parietal, and occipital. Manyof the latter features appear to be related to an overallincrease in endocranial volume, which seems to become

accentuated during the course of the Middle pleistocene.

The face, when preserved, is intermediate in mean valuesmeasuring total projection between Horno erectus andthose of later humans, and there is an increase in midfa_cial projection in several specimens, which is linked withgreater nasal prominence. The postcranial skeleton ispoorly known at present but retains features of Homoerectus, such as an external iliac buttress (Stringeq1986b) and the relatively high levels ofcortical thicken-ing and femoral-shaft width found in archaic Homo gen-erally (Ruff et al., 1993). There are, as yer, no dara onbody proportions to compare with the linear, heat-adapted physique inferred for the much earlier wr 15000Homo erectus individual (Rufl l99l).

In light of remarkable new finds from Atapuerca (Ar_suaga et a1., 1993; Stringer, 1993a), the status of theEuropean Middle Pleistocene sample is currently thesubject of some discussion. Extensive cranial and post-

525

30,000

50,000

t00,000

250,000

500,000

1,000,000

BONDIR$VE S|(HUI.

Kr.a5tt5

0M0.1{B6H QAFZtll

Fig' 36'l' Distuibufon of some imporlonl Pleislocene fosil hominids in lime ond spore. My loxonomk preferenre h lo coll morph A Homo erectus; B Hono

ond D Hono sopiens.

F

526 Stringer

cranial samples dated at ca. 200-300 kyr certainly show the suite of more derived, non-erectus features listed above, but they are combined with apparent Neanderthal characters of the face, occipital, mandible, and pubic ramus. The last item may turn out to be a plesiomorphy as more data become available, but the other features seem to represent real synapomorphies with the Nean-derthals. If, as I advocate, the Neanderthal Glade is given separate, specific status, then we can apparently date the origins of that species in the middle Pleistocene. By a reasonable extension of the variation found in the At-apuerca sample, it is possible that problematic European fossils such as Vertesszolliis, Steinheim, Arago, and Pe-tralona will be drawn into the same general Middle Pleis-tocene lineage, and hence, for me, into the species Homo neanderthalensis. If the Mauer mandible were included, this would mean the end of the concept of a common Middle Pleistocene European-African species based on specimens such as Mauer, Petralona, Bilzingsleben, and Broken Hill, that is, Homo heidelbergensis (cf. Stringer, 1985; Rightmire, 1990). However, new discoveries from Atapuerca (Gran Dolina) and Boxgrove (England) will also be important to a resolution of the status of Homo heidelbergensis.

If Homo neanderthalensis is the sister species of Homo sapiens, then dating the origin of the Homo nean-derthalensis lade would also date the origin of our own separate Glade. But non-European specimens such as Broken Hill (Zambia) and Dali and Yunxian (China) provide little basis for recognizing synapomorphies with Homo sapiens. If the fossils are not regarded as represent-ing Homo heidelbergensis, Homo neanderthalensis, or Homo sapiens, another taxon would need to be recog-nized here; based on the priorities of African names, Homo rhodesiensis or Homo helmei (for Florisbad) are available. When we move into the late Middle Pleisto-cene, there is evidence of possible modern synapomor-phies in Chinese fossils such as Dali and Jinniu Shan and especially in African specimens such as Irhoud 2 and Omo-Kibish 2. The dating of these specimens is still uncertain, although it is likely that there was a temporal overlap with Homo erectus in China prior to 200 kyr (fig. 36.1; see also Chen and Zhang, 1991). Members of the African "late archaic" group such as Irhoud, Singa, and Ngaloba (Laetoli hominid 18) have been dated absolutely to between ca. 100-190 kyr (for Irhoud and Singa, see fig. 36.2).

The Neanderthals

Because of the introduction of the practice of burial by about 100 kyr, we are fortunate to have good data on the body form of both late Neanderthals and early Homo sapiens in western Eurasia. Neanderthal body form com-bined the general pattern of skeletal robusticity known from early Homo skeletal material with what, in modern terms, was certainly a cold-adapted body shape. Trin-kaus's data on limb proportions (fig. 36.3), Holliday's data on limb / trunk proportions (Holliday and Trinkaus, 1991), and Ruff's data on pelvic width relative to stature (Ruff, 1991) show that Neanderthals resembled modern samples from high latitudes in body proportions, as char-acterized by a long and relatively wide trunk and short extremities. This body form would fit with their long-term adaptation to Eurasian climatic regimes that were predominantly cooler than the present interglacial. Ne-anderthals from both Europe and western Asia follow the pattern of modern high-latitude samples (fig. 36.3), in contrast to the WT 15000 Homo erectus skeleton, Broken Hill (inferred from the very long tibia), and the early modern samples. Neanderthal facial form may also have been related to cold adaptation. The configuration of the midface, particularly the voluminous and prominent nose, is unique. It may represent a combination of re-sponses to high activity levels that generate internal heat, inhalation of relatively cold, dry air, and the functional demands of a face resistant to torsion centered around the anterior dentition (cf. Franciscus and Trinkaus, 1988, with Rak, 1986).

The extent to which the Neanderthal Glade evolved in genetic isolation is difficult to establish owing to the lack of good comparative data from other regions, but in the Late Pleistocene, Neanderthals certainly existed as far east as Teshik Tash (Uzbekistan) and were present in the Levant (e.g., Amud, Tabun). The Levantine Nean-derthals were arguably less extreme than their European counterparts in the brachial index and in certain cranial features, but I believe they show enough significant syn-apomorphies to warrant classification as Homo nean-derthalensis. This similarity raises the question of their precise relationship to the European group. It has been argued (e.g., Bar-Yosef, this vol.) that the Asian Nean-derthals moved into this region as a refuge from increas-ingly severe climatic conditions in Europe after about 70 kyr and that before this time the Levant may have been occupied by an evolving lineage of Homo sapiens, repre-

526

cranial samples dated at ca. 200-300 kyr certainly showthe suite of more derived, non-erectus features listedabove, but they are combined with apparent Neanderthalcharacters of the face, occipital, mandible, and pubicramus. The last item may turn out to be a plesiomorphyas more data become available, but the other featuresseem to represent real synapomorphies with the Nean-derthals. If, as I advocate, the Neanderthal clade is givenseparate, specific status, then we can apparently date theorigins of that species in the middle Pleistocene. By a

reasonable extension of the variation found in the At-apuerca sample, it is possible that problematic Europeanfossils such as V6rtessziilliis, Steinheim, Arago, and pe-

tralona will be drawn inro the same general Middle pleis-tocene lineage, and hence, for me, into the species Homoneand,erthalenvs. If the Mauer mandible were inclucied,this would mean the end of the concept of a commonMiddle Pleistocene European-African species based onspecimens such as Mauer, Petralona, Bilzingsleben, andBroken Hill, that is, Homo heidelbergensis (cf. Stringtr,1985; Rightmire, 1990). However, new discoveries fromAtapuerca (Gran Dolina) and Boxgrove (England) willalso be important to a resolution of the statts of Homoheide lbergensis.

If Homo neanderthalensli is the sister species of Homosapiens, then dating the origin of the Homo nean-derthalensis clade would also date the origin of our ownseparate clade. But non-European specimens such as

Broken Hill (Zambia) and Dali and Yunxian (China)provide little basis for recognizing synapomorphies withHorno sapiens. Ifthe fossils are not regarded as represent-ing Homo heidelbergensis, Homo neand.erthalenvi, orHomo sapiens, another taxon would need to be recog-nized here; based on the priorities of African names,Homo rhodesiensis or Homo helmei (for Florisbad) areavailable. When we move into the late Middle pleisto-cene, there is evidence of possible modern synapomor-phies in Chinese fossils such as Dali andJinniu Shan andespecially in African specimens such as Irhoud 2 andOmo-Kibish 2. The dating of these specimens is stilluncertain, although it is likely that there was a temporaloverlap with Homo erectus in China prior to 200 kyr (fig.36.1; see also Chen and Zhang, l99l). Members of theAfrican "late archaic" group such as Irhoud, Singa, andNgaloba (Laetoli hominid 18) have been dated absolutelyto between ca. 100-190 kyr (for Irhoud and Singa, seefi1.36.2).

Stringer

The ileanderthols

Because of the introduction of the practice of burial byabout 100 kyr, we are fortunate to have good data on thebody form of both late Neanderthals and early Hontosapiens in western Eurasia. Neanderthal body form com-bined the general pattern of skeletal robusticity knownfrom early Homo skeletal material with what, inmodernterms, was certainly a cold-adapted body shape. Tiin-kaus's data on limb proporrions (fig. 36.3), Holliday'sdata on limb/trunk proporrions (Holliday and Trinkaus,l99l), and Ruff's data on pelvic width relative to starure(Rufl l99l) show that Neanderthals resembled modernsamples from high latitudes in body proportions, as char_acterized by a long and relatively wide trunk and shortextremities. This body form would fit with their long_term adaptation to Eurasian climatic regimes that werepredominantly cooler than the present interglacial. Ne-anderthals from both Europe and western Asia follow thepattern of modern high-latitude samples (fig. 36.3), incontrast to the wr 15000 Homo erectus skeleton, BrokenHill (inferred from the very long tibia), and the earll,modern samples. Neanderthal facial form may also havebeen related to cold adaptation. The configuration ofthemidface, particularly the voluminous and prominentnose, is unique. It may represent a combination of re_sponses to high activity levels that generate internal heat,inhalation of relatively cold, dry air, and the functionaldemands of a face resistant to torsion centered aroundthe anterior dentition (cf. Franciscus and Tiinkaus,1988, with Rak, 1986).

The extent to which the Neanderthal clade evolved ingenetic isolation is difficult to establish owing to the lackofgood comparative data from other regions, but in theLate Pleistocene, Neanderthals certainly existed as fareast as Teshik Tash (Uzbekistan) and were present in theLevant (e.g., Amud, Thbun). The Levantine Nean-derthals were arguably less extreme than their Europeancounterparts in the brachial index and in certain cranialfeatures, but I believe they show enough significant syn-apomorphies to warrant classification as HomL nean_derthalensil This similariry raises the question of theirprecise relationship to the European group. It has beenargued (e.9., Bar-Yosef, this vol.) that the Asian Nean_derthals moved into this region as a refuge from increas_ingly severe climatic conditions in Europe after about 70kyr and that before this time the Levant may have beenoccupied by an evolving lineage of Homo sapiens, repre-

The Evolution and Distribution of Later Pleistocene Human Populations

527

Fig. 36.2. Chronologies for some later Pleistocene hominid sites in western Eurasia and Africa (adapted from Griin and Stringer, 1991). New Uranium Series (U-S) and Electron Spin Resonance (ESR) dates on mammalian tooth enamel support the early uptake (Ell) ESR age estimates for Tabun, Qafzeh, and Skhul but suggest that there could be an additional younger (oxygen isotope stage 3-4) fauna at Skhul (McDermott et al., 1993).

sented by the probable Middle Pleistocene Zuttiyeh cra-niofacial fragment and the succeeding Qafzeh and Skhul specimens. There are several problems with this argu-ment. First, the Zuttiyeh fossil seems too fragmentary and plesiomorphous for definitive statements about its affinities. Second, Electron Spin Resonance (EsR) and new Uranium Series (U-S) dates for mammalian tooth enamel from layer C at Tabun (McDermott et al., 1993) suggest that the Neanderthal skeleton generally attri-buted to that layer dates from the early Late Pleistocene, making it penecontemporaneous with the Qafzeh speci-mens and significantly older than later Neanderthals from the sites of Kebara and Amud (figs. 36.1, 36.2). Third, it is not clear why European Neanderthal popula-tions, having survived the rigors of oxygen isotope stage 6 in southern Europe, at least, would have been forced out by the less severe conditions of stage 4. Fourth, even if we disregard the third point and propose the need for a

migration into Asia, it is not clear why Neanderthals would not previously have moved into the Levantine refuge during earlier cold stages, for instance, near the end of oxygen isotope stage 6.

Additionally, it seems likely that the most severe cli-matic conditions would have led to a marked restriction of migration routes between Europe and Asia. Although low sea levels would have opened up new migration routes, such as across the Bosphorus and Dardanelles, there would have been the additional obstacles of glaciers and lower or more persistent snow lines in regions such as Turkey and the Caucasus, as well as possible exten-sions of seas such as the Caspian and Aral. If such geo-graphical barriers existed for significant portions of the later Pleistocene, they may explain the distinctive evolu-tion of the Neanderthals in Europe, with the exchange of genes to and from Europe possible during briefer inter-glacial and interstadial stages rather than during the pre-dominant cold stages, when severe selection could have acted on Neanderthal populations isolated in Europe, as Howell (1957) suggested many years ago.

Mode of Origin of Modern Homo Sapiens: Restricted or Multiregional?

I believe the evidence for a recent restricted origin of Homo sapiens is strong, both from considerations of present-day physical and genetic variation and from fos-sil data. Differences between modern crania are predom-inantly those of size rather than shape, whereas shape differences are much more marked between earlier Pleis-tocene samples. Thus, in my opinion, there is a relative decrease in morphological diversity immediately follow-ing the spread of Homo sapiens. As with the genetic data, the overall similarity of modern populations is most par-simoniously explained by recent common ancestry rather than by large, regular, global gene flow. The latter process seems to me to be inherently unlikely under Pleistocene conditions of low population density accom-panied by constantly fluctuating climates, environments, and resources.

Dental morphological data have also been interpreted as favoring a single (although Asian) origin for modern humans. This view is based on phenetic similarities be-tween geographically distant modern samples and on marked contrasts between those samples and supposedly ancestral archaic forms such as the Neanderthals and

The Evoluilon ond Dhhibution of Loter pleislocene Humon populofions527

doo3

o

tig. 36.2. ftronologies for some loter pleislocene hominid siles in westernEurosio ond.Africo {odopted from Gr0n ond Stringer, l99l). New Uronium Series(U-S) ond tledron Spin Resononce (tSR) dotes on rorroiion tooth enomelsuppod fte eorly uphke (EU) tSR oge eslimotes lor lobun, Qofzeh, ond Skhulbd slggesl thot there could be on odditionol younger (oxygen isor;pe stoge3-4) founo ot Skhul (McDermon er ol., 1993i.

sented by the probable Middle pleistocene Zuttiveh cra_niofacial fragment and the succeeding efzeh "r,i

Smulspecimens. There are several problems with this argu_ment. First, the Zuttiyeh fossil seems too fragmentaryand plesiomorphous for definitive statements about itsaffinities. Second, Electron Spin Resonance (rsn) andnew Uranium Series (U-S) dates for mammalian toothenamel from layer C at Thbun (McDermott et al., 1993)suggest that the Neanderthal skeleton generally attri_buted to that layer dates from the early Late pleistocene,making it penecontemporaneous with the efzeh speci_mens and significantly older than later Neanderthalsfrom the sites of Kebara and Amud (figs. 36.1, 36.2).Third, it is not clear why European Neanderthal popula_tions, having survived the rigors ofoxygen isotope stage6 in southern Europe, at least, would have been forcedout by the less severe conditions of stage 4. Fourth, evenifwe disregard the third point and propose the need for a

migration into Asia, it is not clear why Neanderthalswould not previously have moved into the Levantinerefuge during earlier cold stages, for instance, near theend ofoxygen isotope stage 6.

Additionally it seems likely that the most severe cli_matic conditions would have led to a marked restrictionof migration routes between Europe and Asia. Althoughlow sea levels would have opened up new migrationroutes, such as across the Bosphorus and Dardanelles,there would have been the additional obstacles ofglaciersand lower or more persistent snow lines in regions suchas Turkey and the Caucasus, as well as possible exten_sions ofseas such as the Caspian and Aral. Ifsuch geo_graphical barriers existed for significant portions ofthelater Pleistocene, they may explain the distinctive evolu_tion of the Neanderthals in Europe, with the exchange ofgenes to and from Europe possible during briefer inter_glacial and interstadial stages rather than during the pre_dolninant cold stages, when severe selection could haveacted on Neanderthal populations isolated in Europe, asHowell (1957) suggested many years ago.

Mode of 0rigin of Modern Hono Sopiens:Reslricted or Multiregionol?

I believe the evidence for a recent restricted origin ofHomo sapiens is strong, both from considerations ofpresent-day physical and genetic variation and from fos_sil data. Differences between modern crania are predom_inantly those of size rather than shape, whereas shapedifferences are much more marked between earlier pleis_tocene samples. Thus, in my opinion, there is a relativedecrease in morphological diversity immediately follow_ing the spread, of Homo sapiens. As with rhe genetic data,the overall similarity of modern populations is most par_simoniously explained by recent common ancestryrather than by large, regular, global gene flow. The latterprocess seems to me to be inherently unlikely underPleistocene conditions of low population density accom_panied by constantly fluctuating climates, environmenrs,and resources.

Dental morphological data have also been interpretedas favoring a single (although Asian) origin for modernhumans. This view is based on phenetic similarities be_tween geographically distant modern samples and onmarked contrasts between those samples and supposedlyancestral archaic forms such as the Neanderthals and

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The Evolution and Distribution of Later Pleistocene Human Populations

Chinese Homo erectus. Southeast Asia is favored as the ancestral area based on the "average" dental morphology found there (Turner, 1992), but the remaining close phe-netic similarity between African and Australian denti-tions means that assumptions of constant evolutionary rates used by Turner must be wrong. Instead it seems more likely that the close African-Australian relationship is based on symplesiomorphies (Stringer, 1993b; Irish, 1994). Finally, and of great importance, early modern crania from Europe, the Levant, China, Java, and Aus-tralia predominantly resemble neither their archaic pre-decessors nor their recent successors. Instead they share characteristics with one another, which I would interpret as plesiomorphies retained from a recent common ances-try. It is also notable that western Eurasian early moderns display warm-adapted body shapes that contrast mark-edly with those of their Neanderthal counterparts (fig. 36.3). Modern patterns of regional differentiation were apparently poorly developed in early modern humans, thereby implying a recent development of such differen-tiation rather than a long Pleistocene gestation (Stringer, 1992a, 1992b).

Place of Origin of Homo Sapiens

Given the data on body shape mentioned above (and see fig. 36.3), we can infer a tropical or subtropical place of origin for the early Upper Paleolithic peoples of Europe and for the more primitive Levantine Skhul-Qafzeh samples. For the Upper Paleolithic populations, dated at 25-35 kyr, the region of origin could have been the Indian subcontinent, Southeast Asia, or Africa. I favor Africa because of marked similarities between the Late Pleistocene samples of Europe and North Africa (such as Nazlet Khater, Afalou, Taforalt) and the lack of compa-rable data from East Asia. However, the presence of early modern samples penecontemporaneous with those of the European early Upper Paleolithic in regions such as Sri Lanka, Zhoukoudian Upper Cave, and the Willandra Lakes of Australia should instill caution about assigning place of origin and remind us that Europe was by no means a center for modern human origins.

When we consider the Skhul-Qafzeh samples dated at ca. 80-120 kyr (although U-S and esR data indicate that some Skhul fauna may be younger [McDermott et al., 1993]), there are associated faunal data from the sites that do suggest Afro-Arabian connections not so far apparent for Levantine Neanderthal sites (Tchernov, 1992). To-gether with the presence of comparably early modern or

529

near-modern fossils (e.g., Omo-Kibish 1; Guomde KNM-

ER 999 and 3884; Border Cave 3, 5 and, less certainly, 1, 2; Klasies 16424, 16425, 41815) and a feasible ancestral morphology (represented by fossils such as Irhoud 1-3, Omo-Kibish 2, Ngaloba, Eliye Springs, and Florisbad), both scattered across Africa, this region is certainly the most plausible one for the origin for Homo sapiens (Stringer, 1992a, 1992b). However, some caution should be injected because of the lack of good data from other localities. As I have already mentioned, the incomplete preservation of the Zuttiyeh craniofacial fragment makes its status uncertain, and my comparative analyses of cra-nial shape show that the probable late Middle Pleistocene cranium from Dali is not far behind the African late archaics in presenting a plausible ancestral morphology and shape for that of Homo sapiens. However, detailed study of this specimen is not possible at present, and its facie form would certainly look a lot less "modern" if it could be restored to its original proportions. Similarly, the Jinniu Shan partial skeleton is an extremely impor-tant specimen for future study, but it has already been the subject of two quite distinct cranial reconstructions, and its status remains unclear.

Some Questions for Future Research

I have concentrated on western Eurasia in the above discussion of the later Pleistocene hominid record, be-cause this area has the best fossil, chronological and, arguably, paleoenvironmental data for this period; it is also the area with which I am most familiar. I would like to highlight, however, some spheres that remain largely unexplained or unexplored, where future research would be most valuable.

1. Roebroeks et al. (1992) have recently argued that northern European Pleistocene evidence negates claims for major differences in the ecology of human settlement between archaic and modern humans, for example, in the ability to adapt to peak interglacial fully forested condi-tions and to cold loess steppes. I would argue that Upper Paleolithic and comparable populations sustained and developed their occupations of these environments to a much greater extent than did archaic humans. I would also question the evidence for early adaptations to cold steppe in Europe. But how does the Asian record com-pare?

2. Chen and Zhang (1991) have argued that there is good evidence for the coexistence of Homo erectus and "archaic Homo sapiens" in the Middle Pleistocene of

The Evolution snd Disfibution of loter pleistorene Humqn populotions

Chinese Homo erectus. Southeast Asia is favored as theancestral area based on the,,average', dental morphologyfound there (Turner, 1992), but the remaining close phe_netic similarity between African and Australian denti_tions means that assumptions of constant evolutionaryrates used by Turner must be wrong. Instead it seemsmore Iikely that the close African_Australian relationshipis based on symplesiomorphies (Stringer, 1993b; Irish,1994). Finally, and of grear imporrance, early moderncrania from Europe, the Levant, China, Java, and Aus_tralia predominantly resemble neither their archaic pre_decessors nor their recent successors. Instead they sharecharacteristics with one another, which I would inrerpreras plesiomorphies retained from a recent common ances_try. It is also notable that western Eurasian earlv modernsdisplay warm-adapted body shapes that contrast mark_edly with those of their Neanderthal counterparts (fig.36.3). Modern patterns of regional differentiation wereapparently poorly developed in early modern humans,thereby implying a recent development of such differen_tiation rather than a long pleistocene gestation (Stringer,1992a,1992b).

Ploce of Origin ol Homo Sopiens

Given the data on body shape mentioned above (and seefig. 36.3), we can infer a tropical or subtropical place oforigin for the early Upper paleolithic peoples of Europeand for the more primitive Levanrine Skhul_eafzehsamples. For the Upper paleolithic populations, dated ar25-35 kyr, the region of origin could have been theIndian subcontinent, Southeast Asia, or Africa. I favorAfrica because of marked similarities between the LatePleistocene samples of Europe and North Africa (such asNazlet Kharer, Afalou, Taforalt) and the lack of compa_rable data from East Asia. However, the presence of earlymodern samples penecontemporaneous with those of theEuropean early Upper paleolithic in regions such as SriLanka, Zhoukoudian Upper Cave, and the WillandraLakes of Australia should instill caution about assigningplace of origin and remind us that Europe was by nomeans a center for modern human origins.

When we consider the Skhul_eafzeh samples dated atca. 80-120 kyr (although U-S and ESR dara indicate thatsome Skhul fauna may be younger [McDermott et al.,19931), rhere are associated faunal data from the sites thatdo suggest Afro-Arabian connections not so far apparenrfor Levantine Neanderthal sites (Tchernov, lO9Z1. To_gether with the presence of comparably early modern or

near-modern fossils (e.g., Omo_Kibish 1; Guomde rilu_rn 999 and 3884; Border Cave 3, 5 and, less certainly, 1, 2;Klasies 16424,16425, 41815) and a feasible ancesrralmorphology (represented by fossils such as Irhoud l_3,Omo-Kibish 2, Ngaloba, Eliye Springs, and Florisbad),both scattered across Africa, this region is certainly themost plausible one for the origin for Homo sapiens(Stringer, 1992a, 1992b). However, some caution shouldbe injected because of the lack of good data from otherlocalities. As I have already mentioned, the incompletepreservation of the Zuttiyeh craniofacial fragment makesits status uncertain, and my comparative analyses of cra_nial shape show that the probable late Middle pleistocenecranium from Dali is not far behind the African latearchaics in presenting a plausible ancestral morphologyand shape for that of Homo sepiens. However, detailedstudy of this specimen is not possible at present, and itsfacial form would certainly look a lot less ,,modern,, if itcould be resrored to its original proportions. Similarly,the Jinniu Shan partial skeleton is an exrremely impor_tant specimen for future study. but it has already been thesubject oftwo quite distinct cranial reconstruc;ions, andits status remains unclear.

Some 0uestionr for Fulure Reseorch

I have concentrated on western Eurasia in the abovediscussion of the later pleistocene hominid record, be_cause this area has the best fossil, chronological and,arguably, paleoenvironmental data for this period; it isalso the area wirh which I am mosr familiar. i would liketo highlight, however, some spheres that remain largelyunexplained or unexplored, where future research wouldbe most valuable.

l. Roebroeks et al. (1992) have recently argued thatnorthern European pleistocene evidence negates claimsfor major differences in the ecology of human settlementbetween archaic and modern humans, for example, in theability to adapt to peak interglacial fully forested condi_tions and to cold loess sreppes. I would .rgue thrt UpperPaleolithic and comparable populations susrained anddeveloped their occupations ofthese environments to amuch greater extent than did archaic humans. I wouldalso question the evidence for early adaptations to coldsteppe in Europe. But how does the Asian record com_parel

2. Chen and Zhang (1991) have argued that there isgood evidence for the coexistence of Homo erectus and"archaic Homo sapiens" in the Middle pleistocene of

529

530 Stringer

China. I remain slightly cautious, while awaiting further dating evidence, but have previously argued for such contemporaneity in my comparisons of the eastern and western Old World records. If we accept this, and the validity of Homo erectus as a distinct species, there must have been cladogenesis in the hominid lineage by this time. However, could such distinct populations have co-existed in the same regions of Eurasia for any length of time? This certainly happened in the case of many closely related species of mammals in Africa during the Middle and later Pleistocene (Vrba, pers. comm.).

3. Linked with the last point, a late Middle to early Late Pleistocene date for the Ngandong (Solo) hominids seems likely, and they probably represent a late form of Homo erectus. To what extent was Java, as part of Pleisto-cene Sundaland, isolated from mainland Asia during the later Pleistocene? Van Andel (1989) depicts a wide Sun-daland, one traversed by major rivers and subject to a more seasonal and drier climate than today's, which might have opened up the dense rain forests. This condi-tion should have facilitated gene flow, but what was the predominant climatic and paleogeographic situation in this region during the later Pleistocene?

4. Comparing the "Out of Africa" and multiregional models: one model postulates the existence of largely separate hominid evolutionary lineages in different parts of the Old World, whereas the other requires regular and probably large-scale gene flow between all the inhabited regions. What have been the major factors encouraging or discouraging interregional gene flow during the Pleis-tocene? Can evidence from modern biogeography of faunal distributions and provinces provide useful com-parative data here? There certainly appear to be useful analogues from other wide-ranging mammalian species (Vrba, pers. comm.; Groves, 1992).

5. If the "Out of Africa" model is largely accurate, what special factors could have led to the evolution of Homo sapiens in Africa, and what climatic or other factors could have led to Late Pleistocene dispersal events from there? In particular, can we reliably reconstruct North African paleoenvironments for oxygen isotope stages 4-6 by extrapolating from Late Pleistocene and Holocene data?

6. What behavioral or climatic factors could lie be-hind the early Late Pleistocene human population growth inferred from modern mtDNA diversity patterns (Harpending et al., 1993)? Genetic data can also be used to suggest a more complex multistaged dispersal pattern

from Africa (cf. Cavalli-Sforza, 1991, with Nei and Roychoudhury, 1993). Is there evidence for a primary Asian-Australian dispersal through tropical and sub-tropical regions, followed by a separate European and/ or Asian diversification?

7. Given the apparent arrival of humans in Australia through open-sea crossings by 50 kyr, could the Mediter-ranean have remained a significant biogeographic barrier between hominid populations in Europe and North Af-rica throughout the Late Pleistocene? Evidence of a late surviving Neanderthal population in southern Spain at Zaffaraya suggests that the (then-narrower) Straits of Gibraltar had not been crossed even by that time.

Summary We have evidence that once Homo erectus dispersed from its assumed African homeland, regional evolution oc-curred under the constraints of local climatic conditions. The Neanderthals, in particular, are the first hominids known to show clear morphological evidence of cold ad-aptation. Modern humans appear to have had a single origin from a tropical/subtropical environment. Based on fossil and chronometric data, the region of origin probably lies in Africa or the Levant, although genetic analyses continue to favor Africa. We have much to learn, however, about the processes that produced Homo sapiens

and shaped its dispersal and regional diversification.

Acknowledgments

I wish to thank the organizers and sponsors of the Airlie Conference for an excellent meeting in beautiful surroundings. For their assistance with this chapter I thank Rainer &tin, of the Australian National University, for the use of figure 36.2; Robert Kruszynski and Barbara West, for preparing figures 36.1 and 36.3; and Mrs Irene Baxter, for preparing the manuscript.

References Arsuaga, J.-L., Martinez, I., Gracia, A., Carretero, J.-M., and

Carbonell, E. 1993. Three new human skulls from the Sima de los Huesos Middle Pleistocene site in Sierra de Atapuerca, Spain. Nature 362:534-537.

Barstra, Soegondho, S., and Van der Wijk, A. 1988. Ngan- dong Man: Age and artifacts. Journal of Human Evolution 17:325-337.

Bonifay, E., and Vandermeersch, B. (eds.). 1991. Les premiers Europeens. Editions du Comite des Travaux Historiques et Scientifiques, Paris.

Cavalli-Sforza, L. L. 1991. Genes, peoples and languages. Scien-tific American 265(5):71-78.

530Slringer

China. I remain slightly cautious, while awaiting furtherdating evidence, but have previously argued for suchcontemporaneity in my comparisons of the eastern andwestern Old World records. If we accept this, and thevalidity of Homo erectus as a distinct species, there musthave been cladogenesis in the hominid lineage by thistime. However, could such distinct populations have co_existed in the same regions of Eurasia for any length oftime? This certainly happened in the case ofmany closelyrelated species of mammals in Africa during the Middleand later Pleistocene (Vrba, pers. comm.).

3. Linked with the lasr point, a late Middle to earlyLate Pleistocene dare for the Ngandong (Solo) hominidsseems likely, and they probably represent a late form ofHomo erectus. To what extent wasJava, as part of pleisto_cene Sundaland, isolated from mainland Asia during thelater Pleistocenel Van Andel (1989) depicts a wide Sun_daland, one traversed by major rivers and subject to amore seasonal and drier climate than today's, whichmight have opened up the dense lain foresrs. This condl_tion should have facilitated gene flow, but what was thepredominant climatic and paleogeographic situation inthis region during the later pleistocenel

4. Comparing the,,Out of Africa" and multiregionalmodels: one model postulates the existence of largelyseparate hominid evolutionary lineages in different partsof the Old World, whereas the other requires regular andprobably large-scale gene flow between all the inhabitedregions. What have been the major factors encouragingor discouraging interregional gene flow during the pleis_tocene? Can evidence from modern biogeography offaunal distributions and provinces provide useful com_parative data herel There certainly appear to be usefulanalogues from other wide-ranging mammalian species(Vrba, pers. comm.; Groves, 1992).

5. If the "Out of Africa" model is largely accurare,what special factors could have led to the evolution ofHomo sapiens in Africa, and what climatic or other factorscould have led to Late Pleistocene dispersal events fromtherel In particular, can we reliably reconstruct NorthAfrican paleoenvironments for oxygen isotope stages 4_6 by extrapolating from Late pleistocene and Holocenedata?

6. What behavioral or climatic factors could lie be_hind the early Lare pleistocene human populationgrowth inferred from modern mtDNA diversity patterns(Harpending et al., 1993)l Genetic dara can also be usedto suggest a more complex multistaged dispersal pattern

from Africa (cf. Cavalli-Sforza, 1991, with Nei andRoychoudhury, 1993). Is there evidence for a primaryAsian-Australian dispersal through tropical and sub_tropical regions, followed by a separate European andlor Asian diversificationl

7. Given the apparent arrival of humans in Australiathrough open-sea crossings by 50 kyr, could the Mediter_ranean have remained a significant biogeographic barrierbetween hominid populations in Europe and North Af_rica throughout the Late pleistocene? Evidence of a latesurviving Neanderthal population in southern Spain atZaffaraya suggests that the (then_narrower) Straits ofGibraltar had not been crossed even by that time.

Sumnary

We have evidence that once Homo erectus dispersed fromits assumed African homeland, regional evolution oc_curred under the constraints oflocal climatic conditions.The Neanderthals, in particular, are the first hominidsknown to show clear morphological evidence ofcold ad_aptation. Modern humans appear to have had a singleorigin from a tropical,/subtropical environmenr. Basedon fossil and chronometric data, the region of originprobably lies in Africa or rhe Levant, although geneticanalyses continue to favor Africa. We have much to learn,however, atrout the processes that pr oduced Homo sapiensand shaped its dispersal and regional diversification.

Acknowledgments

I wish to thank the organizers and sponsors of the AirlieConference for an excellent meeting in beautiful surroundings.For their assistance with this chapter I thank Rainer Griin, of.the Australian National University, for the use of figure 36.2;Robert Kruszynski and Barbara West, for preparing figures 36.iand 36.3; and Mrs Irene Baxter, for preparing the manuscript.

References

Arsuaga, J.-L., Martinez, I., Gracia, A., Carretero, J._M., andCarbonell, E. 1993. Three new human skulls from the Simade los Huesos Middle pleistocene site in Sierra de Atapuerca,Spiln. Nature 362:534-53j.

Barstra, G.-J., Soegondho, S., and Van der Wiik, A. 19gg. Ngan-dong Man: Age and artifacts. Journal of Human Eoolution17:325-337.

Bonifay, E., and Vandermeersch, B. (eds.). 1991. Les premiersEurop6ens. Editions du Comit6 des tavaux Historiques etScientifiques, Paris.

Cavalli-Sforza, L. L. 1991. Genes, peoples and languages. Sriez_tif. c Americ an 265(5):7 I -7 8.

The Evolution and Distribution of Later Pleistocene Human Populations 531

Chen, T., and Zhang, Y. 1991. Palaeolithic chronology and pos-sible co-existence of Homo erectus and Homo sapiens in China. World Archaeology 23:147-154.

Franciscus, R. G., and Trinkaus, E. 1988. Nasal morphology and the emergence of Homo erectus. American Journal of Physical Anthropology 75:517-527.

Gabunia, L., and Vekua, A. 1995. A Plio-Pleistocene hominid from Dmanisi, East Georgia, Caucasus. Nature 373:509-512.

Groves, C. P. 1992. How old are subspecies? A tiger's eye-view of human evolution. Archaeology in Oceania 27:153-160.

Grun, R., and Stringer, C. 1991. Electron spin resonance dating and the evolution of modern humans. Archaeometry 33:153-199.

Harpending, H. C., Sherry, S. T., Rogers, A. R., and Stoneking, M. 1993. The genetic structure of ancient human populations. Current Anthropology 34:483-496.

Holliday, T., and Trinkaus, E. 1991. Limb/trunk proportions in Neandertals and early anatomically modern humans. American Journal of Physical Anthropology, suppl., 12:93-94.

Howell, F. C. 1957. The evolutionary significance of variation and varieties of "Neanderthal" Man. Quarterly Review of Biol-ogy 32:330-347.

Irish, J. D. 1994. The African dental complex: Diagnostic morphological variants of modern sub-Saharan populations. American journal of Physical Anthropology, suppl., 18:112.

McDermott, E, Griin, R., Stringer, C. B., and Hawkesworth, C. J. 1993. Mass-spectrometric U-series dates for Israeli Ne-anderthal/early modern hominid sites. Nature 363:252-255.

Nei, M., and Roychoudhury, A. K. 1993. Evolutionary relation-ships of human populations on a global scale. Molecular Biology and Evolution 10:927-943.

Rak, Y. 1986. The Neanderthal: A new look at an old face. jour-nal of Human Evolution 15:131-164.

Rightmire, G. P. 1990. The evolution of Homo erectus. Cam-bridge University Press, Cambridge. . 1993. Variation among early Homo crania from Olduvai

Gorge and the Koobi Fora region. American Journal of Physi-cal Anthropology 90:1-33.

Roebroeks, W, Conard, N. J., and van Kolfschoten, T 1992. Dense forests, cold steppes, and the Palaeolithic settlement of northern Europe. Current Anthropology 33:551-586.

Ruff, C. 1991. Climate, body and body shape in hominid evolu-tion. journal of Human Evolution 21:81-105. . 1993. Climatic adaptation and hominid evolution: The

thermoregulatory imperative. Evolutionary Anthropology 2:53-59.

Ruff, C., Trinkaus, E., Walker, A., and Larsen, C. S. 1993. Post-cranial robusticity in Homo 1: Temporal trends and mechanical interpretation. American Journal of Physical An-thropology 91:21-53.

Stringer, C. B. 1985. Middle Pleistocene hominid variability and the origin of late Pleistocene humans. In Ancestors: The hard evidence, pp. 289-295 (ed. E. Delson). Liss, New York. . 1986a. An archaic character in the Broken Hill innomi-

nate E. 719. American journal of Physical Anthropology 71:115-120. . 1986b. The credibility of Homo habilis. In Major topics

in primate and human evolution, pp. 266-294 (ed. B. Wood, L. Martin, and P. Andrews). Cambridge University Press, Cam-bridge. . 1992a. Replacement, continuity and the origin of Homo

sapiens. In Continuity or replacement: Controversies in Homo sa-piens evolution, pp. 9-24 (ed. G. Brauer and E H. Smith). Balkema, Rotterdam. . 1992b. Reconstructing recent human evolution. Phil.

Trots. R. Soc. Lund. B 337:217-224. . 1993a. Secrets of the Pit of the Bones. Nature 362:501-

502. . 1993b. Understanding the fossil human record: Past,

present and future. Rivista di Antropologia 71:91-100. Swisher, C., Curtis, G., Jacob, T, Getty, A., Supriio, A., and

Widiasmoro. 1994. Age of the earliest known hominids in Java, Indonesia. Science 263:1118-1121.

Tchernov, E. 1992, Biochronology, paleoecology and dispersal events of hominids in the southern Levant. In The evolution and dispersal of modern humans in Asia. pp. 149-188 (ed. T. Akazawa, K. Aoki, and T Kimura). Hokusen-Sha, Tokyo,

Trinkaus, E. 1981. Neanderthal limb proportions and cold adap-tation. In Aspects of human evolution, pp. 187-224 (ed. C. B. Stringer). Taylor and Francis, London.

Turner, C. G. 1992. The dental bridge between Australia and Asia: Following Macintosh into the East Asian hearth of hu-manity. Archaeology in Oceania 27:143-152.

Van Andel, T. H. 1989. Late Quaternary sea-level changes and archaeology. Antiquity 63:733-745.

Wood, B. 1992. Origin and evolution of the genus Homo. Nature 355:783-790.

The Evolufion ond Dislribufion of loler Pleistorene Humon populofions

Chen, T, and,Zhang, Y. 1991. Palaeolithic chronology and pos_sible co-existence of Homo erectus and, Homo sapiens in China.Wor ld Arc hae o lo gy 23 :l 47 -l 54.

Franciscus, R. G., and Trinkaus, E. 1988. Nasal morphology andthe emergence of Homo erectus. American Journal of phlysicat

Anthropology 7 5:517 -527.Gabunia, L., and Vekua, A. 1995. A Plio-pleistocene hominid

lrom Dmanisi, East Georgia, Caucasus. Nature 373:509_512.Groves, C. P.1992. How old are subspeciesi A tiger,s eye-view

ofhuman evolurion. Archaeologl in Oceania 27:153_160.Griin, R., and Stringer, C. 1991. Electron spin resonance dating

and the evolution ofmodern humans. Archaeometry 33:153_199.

Harpending, H. C., Sherry, S. T, Rogers, A. R., and Stoneking,M. 1993. The genetic structure of ancient human populations.C ur rent Ant hro p o lo gy 34:483 -49 6.

Holliday T,, and tinkaus, E. 1991. Limb/trunk proporrions inNeandertals and early anatomically modern humans. AmericanJournal af Physical Anthropologt, suppl., 12:93-94.

Howell, E C. 1957. The evolutionary significance of variationand varieties of "Neanderthal" Man. etarterll Recieo of Biol-ogy 32:330-347.

Irish, J. D. 1994. The Alrican dental complex: Diagnosticmorphological varianrs of modern sub-Saharan populations.Americ an Journal of P hy si c a t Ant hro p o lo gy, suppl., 1

g: 1 I 2.McDermott, E, Griin, R., Stringer, C. 8., and Hawkesworth,

C. J. 1993. Mass-spectrometric U-series dates for Israeli Ne_anderthal/ early modern hominid sircs. N ature 363:Z5Z-255.

Nei, M., and Roychoudhury, A. K. 1993. Evolutionary relation_ships ofhuman populations on a global scale. t\[oletularBiology awl Eaolution 10:927-943.

Rak, Y. 1986. The Neanderthal: A new look at an old face. Jour_nal of Human Eaolution 15:131-164.

Rightmire, G. P. 1990. The eaolution ofHomo erectus. Cam_bridge University Press, Cambridge.

1993. Variation among earlv Homo crania from OlduvaiGorge and the Koobi Fora region. American Journat of physi_

c al Antltropology 90: I -33.Roebroeks, W., Conard, N. J., and van Kolfschoten,-t. lggL.

Dense forests, cold steppes, and the palaeolithic settiement ofnorthern Europe. Current Anthropotogy 33:551-5g6.

Ruff, C. 1991. Climate, body and body shape in hominid evolu_tion. Journal d Human Eztolution Zl:81-105.

1993. Climatic adaptation and hominicl evolution: The

thermoregulatory imperative. Eaolutionary Anthropology 2:53_59.

Rufl C., tinkaus, E., Walker, A., and Larsen, C. S. 1993. post_

cranial robusticity in Homo l: Temporal trends andmechanical interpretation. American Journal o-f phlsical An-thropology 91:21-53.

Stringer, C. B. 1985. Middle Pleistocene hominid variability andthe origin of late Pleistocene humans. InAncestors: The hartletidence, pp.289-295 (ed. E. Delson). Liss, New york.

1986a. An archaic character in the Broken Hill innomi_nate E. 719. American Journal of physical Anthrtplllg/71:115-120.

1986b. The credibility of Homo habitis. ln Major topicsin primate and human eaolution, pp. 266-294 (ed. B. Wood, L.Martin, and P Andrews). Cambridge University press, Cam_bridge.

i992a. Replacemenr, conrinuity and the origin of Homosapiens. In Continuitlt or replacement: Controu^ersiesiz Homo sa_piens eoolution, pp.9*24 (ed. G. Brduer and E H. Smith).Balkema, Rotterdam.

1992b. Reconstructing recent human evolution. piil.Tiafis. R. Soc. Lond.B337:217-224.

1993a. Secrets ofthe pit ofthe Bones. Nature 362:501_502.

1993b. Understanding the fossil human record: past,present and fuure. Riaista di Antropologia 7l:91_100.

Swisher, C., Curtis, G., Jacob, T, Getty, A., Suprijo, A., andWidiasmoro. 1994. Age of the earliest known hominids inJava, Indonesia. Science 263:1 1 l8-1 121.

Tchernov, E. 1992. Biochronology, paleoecology and dispersalevents ofhominids in the southern Levant. In The eaolutionand dispersal of modern humans in Asia. pp. 149_18g (ed. T,Akazawa, K. Aoki, and T, Kimura). Hokusen-Sha, Tokyo.

tinkaus, E. 1981. Neanderthal limb proportions and cold adap_t^tion. In Aspects of human ez;olution, pp. 187 _224 (ed. C. B.Stringer). tylor and Francis, London.

Turner, C. G. 1992. The dental bridge between Australia andAsia: Following Macintosh into the East Asian hearth of hu-manity Archaeology in Oceania 27:143-152.

Van Andel, T H. 1989. Late Quaternary sea-level changes andarchaeology. Antiquitl 63:7 33 -7 45.

Wood, B. 1992. Origin and evolution of the genus Homo. Nature355:783-790,

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