The absolute dating of Upper Pleistocene subSaharan fossil hominids and their place in human evolution

In the evolution of anatomically modern man and his subspecies most specialists have concentrated on investigating geographical areas other than Africa as the possible area of origin.In this study 20 fossil hominids and associated faunal remains from South and East Africa were dated by microanalysis, radiocarbon, and amino-acid dating in order to see whether modern man appears later, was sympatric, or even predated Neandertal man.These dates indicate that anatomically modern man occurs sympatrically and possibly even predates the Rhodesian group of Neandertals in Africa. Modern man might also be contemporary to and possibly even predate the occurrence of Neandertal in Europe.This would indicate that modern man did not evolve from but possibly gave rise to the Neandertals as off-shoots.Two possibilities for the evolution of modern man are suggested. First, that Homo sapiens capensis evolved about 90,000 to 100,000 years ago from possibly Homo erectus by way of a “basic” Homo sapiens and later gave rise to Homo sapiens rhodesiensis, Homo sapiens afer, and possibly Homo sapiens palestinus around 50,000 years ago with Homo neanderthalensis and Homo sapiens capensis evolving separately from Homo erectus. In this case Homo neanderthalensis would be a different species from Homo sapiens which includes Homo sapiens capensis, Homo sapiens rhodesiensis, Homo sapiens afer, and possibly Homo sapiens palestinus.Secondly, Homo sapiens capensis evolved by way of a “basic” Homo sapiens with Homo sapiens rhodesiensis and Homo sapiens palestinus branching off from Homo sapiens capensis around 50,000 years ago. Before that, around 90,000 to 100,000 years ago Homo sapiens capensis evolved first and was then followed by Homo sapiens neanderthalensis from a “basic” Homo sapiens stock, but diverged. This means, all Neandertals, Homo sapiens capensis, Homo sapiens sapiens and Homo sapiens afer can be considered as subspecies of Homo sapiens.The author favors the first scheme since on relative dating grounds the existence of Neandertal man in Europe before the earliest date of Homo sapiens capensis and a “basic” Homo sapiens seems to be fairly well documented. Irrespective of either one of these possibilities, modern man evolved in Africa and seems to have migrated into Europe and other parts of the world.New absolute dating techniques are mentioned in detail like the new radiocarbon-collagen method and amino acid dating.     

Another nail in the coffin of the multiple-origins theory?

While mitochondrial sequences can be used to probe the time and place of the mitochondrial ‘Eve,’ nuclear genes can be used to ask a slightly different question: when did humans (members of the genus Homo) or their hominid precursors (the hominids) first leave Africa and fan out over Asia and Europe? If they did so recently, it seems likely that there was a recent African origin of our species, Homo sapiens, rather than multiple origins in various parts of the Old World. A recent paper⁽¹⁾ uses minisatellite data to make the argument that the departure from Africa happened very recently indeed. An alternative explanation for the data is that there was no single and irreversible departure from Africa, but that some peoples migrated back and forth between Africa and the rest of the Old World over the last few tens of thousands of years. For this and other reasons, putting a single date on the farewell to Africa remains problematical.     

Multiple dispersals and modern human origins

Despite a massive endeavour, the problem of modern human origins not only remains unresolved, but is usually reduced to “Out of Africa” versus multiregional evolution. Not all would agree, but evidence for a single recent origin is accumulating. Here, we want to go beyond this debate and explore within the “Out of Africa” framework an issue that has not been fully addressed: the mechanism by which modern human diversity has developed. We believe there is no clear rubicon of modern Homo sapiens, and that multiple dispersals occurred from a morphologically variable population in Africa. Pre-existing African diversity is thus crucial to the way human diversity developed outside Africa. The pattern of diversity—behavioural, linguistic, morphological and genetic—can be interpreted as the result of dispersals, colonisation, differentiation and subsequent dispersals overlaid on former population ranges. The first dispersals would have originated in Africa from where two different geographical routes were possible, one through Ethiopia/Arabia towards South Asia, and one through North Africa/Middle East towards Eurasia.     

Neandertals and moderns mixed,and it matters

Twenty‐five years ago, the Middle‐to‐Upper Paleolithic transition in Europe could be represented as a straightforward process subsuming both the emergence of symbolic behavior and the replacement of Neandertals by modern humans. The Aurignacian was a proxy for the latter, during which enhanced cognitive capabilities explained ornaments and art. The few instances of Neandertal symbolism were deemed to long postdate contact and dismissed as “imitation without understanding,” if not geological contamination. Such views were strengthened by the recent finding that, in southern Africa, several features of the European Upper Paleolithic, including bone tools, ornaments, and microliths, emerged much earlier. Coupled with genetic suggestions of a recent African origin for extant humans, fossil discoveries bridging the transition between “archaics” and “moderns” in the realm of anatomy (Omo‐Kibish, Herto) seemingly closed the case. Over the last decade, however, taphonomic critiques of the archeology of the transition have made it clear that, in Europe, fully symbolic sapiens behavior predates both the Aurignacian and moderns. And, in line with evidence from the nuclear genome rejecting strict replacement models based on mtDNA alone, the small number of early modern specimens that passed the test of direct dating present archaic features unknown in the African lineage, suggesting admixture at the time of contact. In the realm of culture, the archeological evidence also supports a Neandertal contribution to Europe's earliest modern human societies, which feature personal ornaments completely unknown before immigration and are characteristic of such Neandertal‐associated archeological entities as the Châtelperronian and the Uluzzian. The chronometric data suggest that, north of the Ebro divide, the entire interaction process may have been resolved within the millennium centered around 42,000 calendar years ago. Such a rapid absorption of the Neandertals is consistent with the size imbalance between the two gene reservoirs and further supports significant levels of admixture.     

Time and biosequences: a contribution to the origin of modern man

The origin of modern man is still a highly debated problem. The new contributions of molecular biologists to paleontological data are numerous but discordant as these data obtained with biosequences are based on different methodologies. In order to obtain a more accurate measure of the genetic distance between extant humans and thus the deepest root of the human tree, we have reanalyzed the sequences of the regulatory region of mitochondrial DNA (D-loop) by using an improved version of the Markov Clock model devised in our laboratory. Our analysis, as well as other studies, supports the African origin of modern man. However the quantitative estimate of mtDNA evolution carried out with the corrected Markov Clock model pushes back irradiation time from Africa to 400±100 Kya. Thus according to our model there would be a genetic continuity betweenHomo erectus andHomo sapiens, who would therefore be the result of regional evolution differentiating himself under appropriate environmental pressures.     

Cross-sectional morphology of the SK 82 and 97 proximal femora

Computed tomography scans of the proximal femoral shaft of the South African “robust” australopithecine, A. robustus, reveal a total morphological pattern that is similar to the specimen attributed to A. boisei in East Africa but unlike that of Homo erectus or modern human femora. Like femora attributed to H. erectus, SK 82 and 97 have very thick cortices, although they do not have the extreme increase in mediolateral buttressing that is so characteristic of H. erectus. And unlike H. erectus or modern humans, their femoral heads are very small relative to shaft strength. These features are consistent with both increased overall mechanical loading of the postcranial skeleton and a possibly slightly altered pattern of bipedal gait relative to that of H. erectus and modern humans. Am J Phys Anthropol 109:509–521, 1999. © 1999 Wiley-Liss, Inc.     

The Middle/Later Stone Age transition and cultural dynamics of late Pleistocene East Africa

The Middle to Later Stone Age (MSA/LSA) transition is a prominent feature of the African archeological record that began in some places ~30,000–60,000 years ago, historically associated with the origin and/or dispersal of “modern” humans. Unlike the analogous Middle to Upper Paleolithic transition in Eurasia and associated Neanderthal extinction, the African MSA/LSA record remains poorly documented, with its potential role in explaining changes in the behavioral diversity and geographic range of Homo sapiens largely unexplored. I review archeological and biogeographic data from East Africa, show regionally diverse pathways to the MSA/LSA transition, and emphasize the need for analytical approaches that document potential ancestor‐descendent relationships visible in the archeological record, needed to assess independent invention, population interaction, dispersal, and other potential mechanisms for behavioral change. Diversity within East Africa underscores the need for regional, rather than continental‐scale narratives of the later evolutionary history of H. sapiens.     

Human evolution

The common ancestor of modern humans and the great apes is estimated to have lived between 5 and 8 Myrs ago, but the earliest evidence in the human, or hominid, fossil record is Ardipithecus ramidus, from a 4.5 Myr Ethiopian site. This genus was succeeded by Australopithecus, within which four species are presently recognised. All combine a relatively primitive postcranial skeleton, a dentition with expanded chewing teeth and a small brain. The most primitive species in our own genus, Homo habilis and Homo rudolfensis, are little advanced over the australopithecines and with hindsight their inclusion in Homo may not be appropriate. The first species to share a substantial number of features with later Homo is Homo ergaster, or ‘early African Homo erectus’, which appears in the fossil record around 2.0 Myr. Outside Africa, fossil hominids appear as Homo erectus-like hominids, in mainland Asia and in Indonesia close to 2 Myr ago; the earliest good evidence of ‘archaic Homo’ in Europe is dated at between 600–700 Kyr before the present. Anatomically modern human, or Homo sapiens, fossils are seen first in the fossil record in Africa around 150 Kyr ago. Taken together with molecular evidence on the extent of DNA variation, this suggests that the transition from ‘archiac’ to ‘modern’ Homo may have taken place in Africa.     

Human taxonomic diversity in the pleistocene: Does Homo erectus represent multiple hominid species?

Recently, nomina such as “Homo heidelbergensis” and “H. ergaster” have been resurrected to refer to fossil hominids that are perceived to be specifically distinct from Homo sapiens and Homo erectus. This results in a later human fossil record that is nearly as speciose as that documenting the earlier history of the family Hominidae. However, it is agreed that there remains only one extant hominid species: H. sapiens. Has human taxonomic diversity been significantly pruned over the last few hundred millennia, or have the number of taxa been seriously overestimated? To answer this question, the following null hypothesis is tested: polytypism was established relatively early and the species H. erectus can accommodate all spatio-temporal variation from ca. 1.7 to 0.5 Ma. A disproof of this hypothesis would suggest that modern human polytypism is a very recent phenomenon and that speciation throughout the course of human evolution was the norm and not the exception. Cranial variation in a taxonomically mixed sample of fossil hominids, and in a modern human sample, is analyzed with regard to the variation present in the fossils attributed to H. erectus. The data are examined using both univariate (coefficient of variation) and multivariate (determinant) analyses. Employing randomization methodology to offset the small size and non-normal distribution of the fossil samples, the CV and determinant results reveal a pattern and degree of variation in H. erectus that most closely approximates that of the single species H. sapiens. It is therefore concluded that the null hypothesis cannot be rejected. © 1993 Wiley-Liss, Inc.     

Population structure and the evolution of Homo sapiens in Africa

It has been proposed that a multiregional model could describe how Homo sapiens evolved in Africa beginning 300,000 years ago. Multiregionalism would require enduring morphological or behavioral differences among African regions and morphological or behavioral continuity within each. African fossils, archeology, and genetics do not comply with either requirement and are unlikely to, because climatic change periodically disrupted continuity and reshuffled populations. As an alternative to multiregionalism, I suggest that reshuffling produced novel gene constellations, including one in which the additive or cumulative effect of newly associated genes enhanced cognitive or communicative potential. Eventual fixation of such a constellation in the lineage leading to modern H. sapiens would explain the abrupt appearance of the African Later Stone Age 50–45 thousand years ago, its nearly simultaneous expansion to Eurasia in the form of the Upper Paleolithic, and the ability of fully modern Upper Paleolithic people to swamp or replace non‐modern Eurasians.     

Genetic evidence and the modern human origins debate

A continued debate in anthropology concerns the evolutionary origin of 'anatomically modern humans' (Homo sapiens sapiens). Different models have been proposed to examine the related questions of (1) where and when anatomically modern humans first appeared and (2) the genetic and evolutionary relationship between modern humans and earlier human populations. Genetic data have been increasingly used to address these questions. Genetic data on living human populations have been used to reconstruct the evolutionary history of the human species by considering how global patterns of human variation could be produced given different evolutionary scenarios. Of particular interest are gene trees that reconstruct the time and place of the most recent common ancestor of humanity for a given haplotype and the analysis of regional differences in genetic diversity. Ancient DNA has also allowed a direct assessment of genetic variation in European Neandertals. Together with the fossil record, genetic data provide insight into the origin of modern humans. The evidence points to an African origin of modern humans dating back to 200,000 years followed by later expansions of moderns out of Africa across the Old World. What is less clear is what happened when these early modern humans met preexisting 'archaic human' populations outside of Africa. At present, it is difficult to distinguish between a model of total genetic replacement and a model that includes some degree of genetic mixture.     

A new pleistocene hominid-bearing locality at Hoedjiespunt,South Africa

HDP1 is an archaeological and faunal site located on the Hoedjiespunt peninsula at Saldanha Bay, South Africa, that has recently yielded fossil human remains. Artefacts from the associated archaeological deposits are identified as being Middle Stone Age. U series analysis of capping calcretes and analysis of the foraminifera and fauna associated with the human fossils indicate an age for the deposit in excess of 74,000 years before present, and it most probably dates to around 300,000 years before present. The fossil human teeth from in situ deposits at Hoedjiespunt are described and found to be large by comparison with modern humans but smaller than the known upper dentitions of southern African “archaic” Homo sapiens. The Hoedjiespunt molars are found to be morphologically within the range of variation observed in the teeth of modern Homo sapiens. © 1995 Wiley-Liss, Inc.     

Fossil Humankind and Other Anthropoid Primates of China

More than 70 sites have yielded human fossils in China. They are attributed to Homo sapiens erectus and Homo sapiens sapiens. The earliest one is possibly about 1.7 Ma. A series of common morphological features, including shovel-shaped incisors and flatness of the face, characterize them. There is a morphological mosaic between H. s. erectus and H. s. sapiens in China. The existence of common features and the morphological mosaic suggest continuity of human evolution in China. That there are a few features which are more commonly seen in the Neanderthal lineage, occurring in a few Chinese fossil skulls, probably suggests gene flow between China and the West. Based on them, in 1998 I proposed an hypothesis—continuity with hybridization—for human evolution in China. The hypothesis is supported by paleolithic archeology, and it supports the multiregional evolution hypothesis of modern human origins. The anatomically modern humans of East Asia originated most probably in China. Although some nonhuman anthropoid primates of China—Gigantopithecus, Sivapithecus, Ramapithecus and Lufengpithecus—have been suggested as the direct ancestors of human beings, the discovery of more specimens and further studies do not support these suggestions. Therefore, it is most probable that the transition between apes and humans did not occur in China.     

Zuttiyeh face: A view from the east

We analyze the phylogenetic position of the frontofacial fragment from Zuttiyeh, Israel. This specimen is dated to the Middle Pleistocene (the latest estimate is between 250 and 350 kyr) and is associated with the Acheulo-Yabrudian, which makes it the oldest cranium from the region. It has been previously regarded as a Neandertal, and early “anatomically modern Homo sapiens,” and a generalized specimen ancestral to both. These different phylogenetic interpretations of its features have a historic basis but in our view also result from a confusion of grade and intraspecies clade as valid sources of variation. We show here that generally the differences that distinguish Zuttiyeh from Neandertals are similarities it shares with the Zhoukoudian remains. These similarities involve a unique combination of features, and suggest the possibility of an ancestral relationship. It is less likely that Middle Pleistocene remains from Europe or sub-Saharan Africa are uniquely or significantly ancestral to Zuttiyeh. An accurate understanding of the relationship between populations of eastern and western Asia is important for resolving the more general questions surrounding the position of the Upper Pleistocene Levant populations in human evolution, including (1) whether there are significantly different contemporary Mousterian populations in the Upper Pleistocene, (2) whether Neandertals are clearly intrusive in the region, and (3) whether there is an early appearance of (what many workers call) “anatomically modern Homo sapiens.” The hypothesis of a recent unique African ancestry for all modern humans is disproved by our study, which shows Asia as a significant source area for at least some living populations. © 1993 Wiley-Liss, Inc.     

How big were early hominids?

The recent discovery of new postcranial fossils, particularly associated body parts, of several Plio-Pleistocene hominids provides a new opportunity to assess body size in human evolution.¹ Body size plays a central role in the biology of animals because of its relationship to brain size, feeding behavior, habitat preference, social behavior, and much more. Unfortunately, the prediction of body weight from fossils is inherently inaccurate because skeletal size does not reflect body size exactly and because the fossils are from species having body proportions for which there are no analogues among modern species. The approach here is to find the relationship between body size and skeletal size in ape and human specimens of known body weight at death and to apply this knowledge to the hominid fossils, using a variety of statistical methods, knowledge of the associated partial skeletons of the of early hominids, formulae derived from a modern human sample, and, finally, common sense. The following modal weights for males and females emerge: Australopithecus afarensis, 45 and 29 kg; A. africanus, 41 and 30 kg; A. robustus, 40 and 32 kg; A. boisei, 49 and 34 kg; H. habilis, 52 and 32 kg. The best known African early H. erectus were much larger with weights ranging from 55 kg on up. These estimates imply that (1) in the earliest hominid species and the “robust” australopithecines body sizes remained small relative to modern standards, but between 2.0 and 1.7 m.y.a. there was a rapid increase to essentially modern body size with the appearance of Homo erectus; (2) the earliest species had a degree of body size sexual dimorphism well above that seen in modern humans but below that seen in modern gorillas and orangs which implies (along with other evidence) a social organization characterized by kin-related, multi-male groups with females who were not kin-related; (3) relative brain sizes increased through time; (4) there were two divergent trends in relative cheek-tooth size—a steady increase through time from A. afarensis to A. africanus to the “robust” australopithecines, and a decrease beginning with H. habilis to H. erectus to H. sapiens.     

Middle eastern origin model forHomo sapiens (Moderns & Neanderthals), language and modern behaviour

A new model may resolve the problem of when and where did appear anatomically modern humans. According to this model, Neanderthals were probably neither our ancestor nor different species.Homo sapiens appeared probably in the Middle East, approximately 150 ka ago and differentiated to anatomically modern humans and Neanderthals because of the genetic programme. The fossils older than 150 ka are probably not Neanderthal such as Zuttiyeh and Biache-Saint-Vaast specimens. Cultural capacities of Neanderthals were probably equivalent to Moderns. Most of pre-Homo sapiens populations may be extinct without replacement byHomo sapiens. Language and modern behaviour should have arisen with our own species.     

Middle pleistocene humans from africa

Patterns of human evolution in the Middle Pleistocene remain poorly understood. There is general consensus that by the onset of this time period, populations ofHomo erectus were dispersed from Africa into Eurasia, including the Far East. In the western part of this range (perhaps in Africa),Homo erectus then produced a daughter lineage exhibiting more advanced characters of the face, braincase and cranial base. How this new species should be defined is currently debated. In my view, fossils from sites such as Bodo and Broken Hill in Africa may be lumped with material from earlier Middle Pleistocene localities in Europe. Such a taxon is appropriately namedHomo heidelbergensis. Whether the hypodigm should be extended to include fossils from China is another question. In any case, this group of hominids is plausibly ancestral to both the specialized Neanderthals of Europe and more modern humans of the later Middle Pleistocene.     

A deterministic model of admixture and genetic introgression: the case of Neanderthal and Cro-Magnon

There is an ongoing debate in the field of human evolution about the possible contribution of Neanderthals to the modern human gene pool. To study how the Neanderthal private alleles may have spread over the genes of Homo sapiens, we propose a deterministic model based on recursive equations and ordinary differential equations. If the Neanderthal population was large compared to the Homo sapiens population at the beginning of the contact period, we show that genetic introgression should have been fast and complete meaning that most of the Neanderthal private alleles should be found in the modern human gene pool in case of ancient admixture. In order to test/reject ancient admixture from genome-wide data, we incorporate the model of genetic introgression into a statistical hypothesis-testing framework. We show that the power to reject ancient admixture increases as the ratio, at the time of putative admixture, of the population size of Homo sapiens over that of Neanderthal decreases. We find that the power to reject ancient admixture might be particularly low if the population size of Homo sapiens was comparable to the Neanderthal population size.     

The Indonesian Homo erectus brain endocasts revisited

New brain endocast reconstructions of Homo erectus discoveries from Indonesia since 1963 (H. erectus VI, 1963; VII, 1965; VIII, 1969) have been made and their volumes determined. In addition, older discoveries (H. erectus I, 1891; II, 1937; IV, 1937–38) have been reendocast and reconstructed, and have yielded volumes considerably different from those previously published. This is particularly so in the case of Dubois's original discovery, which yields a volume of 940 ml rather than the widely quoted volume of 750 ml. In addition, a number of morphological observations regarding hemispheric asymmetries (petalias) are provided, which suggest a condition similar to modern Homo sapiens.     

Fossil human crania from Yunxian, China: Morphological comparison withHomo erectus crania from Zhoukoudian

Two fossil hominid crania from Yunxian were found in 1989 and 1990 respectively, and were attributed toHomo eretus. For the purpose of examining the “Homo erectus features” in Yunxian crania, comparisons with crania from Zhoukoudian are made in this paper. The features examined include supraobital tori, occipital torus, angle between the occipital and nuchal planes, postorbital constriction, skull breadth conditions, lowness of skull, and frontal flatness and receding. Results show that the “Homo erectus features” are doubtful owing to damage to and distortion of Yunxian crania. Morphologically, the crania from Yunxian are likely ofHomo sapiens.