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ABSTRACT: Recent finds of hominid fossils and associated archaeological remains throughout the wild are reviewed, and their significance for our understanding of human biological and cultural evolution assessed. Gaps in current knowledge help establish priorities for future research.
It is not possible to comprehend the unique position our own species occupies in the modem world without uncovering and understanding human evolution. As yet, the record is very incomplete, but it is certainly much better understood today than it was when I was a student at Cambridge in the 1930s.
Human evolutionary theory then had little in the way of early human fossils as hard data and hypotheses relied mainly on interpreting the uniqueness of the human species. As a result, we got the Piltdown hoax which seemed to confirm then-current ideas of what amcestral Homo should look like. Imagination ran wild and discoveries of great apes enabled artists to invent behaviour. Since the Second World War, systematic survey and collaboration, in field and laboratory, of natural and earth scientists and archaeologists has added very significantly to understanding the pathways, events and morphological developments of the hominid lineage.
Now, due to the discovery of old land surfaces in Africa and elsewhere that preserve archaeological residues of human activities in near primary context, we are beginning to be able to identify and distinguish evidences of hominid activity from those of other agencies, geological and animal, that accumulated and dispersed concentrations of bones and stone artefacts. With the increasing availability of a tested chronology, basic to any interpretation of biological and cultural evolution, we are beginning to see the relationships between climate and environmental changes in the past and how these seem to have initiated the significant morphological changes seen in the fossils, and in the nature and context of the cultural associations. Many models have been put forward to explain the evolutionary record but all, if they have any value must depend on the hard evidence: the fossils and the archaeological residues and the contexts in which these are found. We have now, particularly for Europe and Africa, where most of the systematic research has been carried out, many more fossils and cultural assemblages. There have been great advances in understanding how and where the modern human species evolved, yet there remains so much more that must be learned if we are to have any confidence in the emerging record, Above all, we need more complete human fossils; much of what we have is fragmentary and therefore liable to alternative reconstructions and interpretations. We need securely associated fossils in firmly dated contexts in the open and in caves, so that when excavations of sealed and minimally disturbed hominid activity areas are carried out, the nature of the patterning - the ways bones, artefacts and site features are interrelated - will begin to provide clues to the activities and the size and length of occupation of the foraging groups that left evidence of their presence. The caveat, therefore, to what I am going to say is that the behavioural hypotheses and arid scenarios are no better than the hard data on which they are based. We must have more of this hard data if we are to firm up the evolutionary record. Almost every year now a significant new human fossil is found that necessitates readjustment of existing tenets and hypotheses. The record is becoming a little clearer, thanks to the collaboration of a widening body of specialists, but also ever more complex the more data we obtain. The scenario available today will surely undergo some major modifications even by the beginning of the new century. This is what science is all about. We will look at some of the bones and related artefact assemblages. We will also look at what molecular biology has to say about, in particular, the origins of anatomically modern humans like ourselves. The fossil, the archaeological and the molecular record have a common research goal and the evidence each contributes has to be considered as part of a whole, not in isolation from one another. Such collaboration is leading to significant advances in knowledge.
All evidence, in spite of some recent claims to the contrary, indicates that the human lineage evolved on the African continent, in the uniquely rich tropical habitats of the African savannah, with a biome of plants and animals unequalled elsewhere. It was here, some five million or more years ago, that our first bipedal ancestors split from the line leading to the African apes. Nowhere else in the world has any evidence of this australopithecine grade been found.
What might be described as the find of the century was made in 1992-3 by my colleague, Tim White and his team in the Afar Rift of Ethiopia. This consisted of seventeen hominid fossil specimens from Pliocene sediments at Aramis that are dated to 4,4 mya: cranial, dental and post-cranial fossils of a hominid that is morphologically and chronologically earlier than Australopithecus afarensis by about 500 000 years (White et al. 1994). The new form was named A. ramidus and its primitive morphology suggests that it represents a long sought root species for the Hominidae. A partial skeleton from the same horizon found in the last weeks of the 1994 season is a very significant find. Tim White and his co-arthors consider these finds justify generic separation from Australopithecus and they have now given the Aramis fossils the generic name Ardipithecus (‘ardi’ means ‘ground’ or root’ in the Afar language) (White el al. 1995). When the analysis of the new specimen is completed, as so much of this individual is present, the features that distinguish Ardipithecus from Australopithecus and from the chimpanzee will be clearly demonstrated. The sediments, botanical and faunal evidence from Aramis suggest Ardipithecus ramidus lived in a wooded habitat with more open countzy not far away (WoldeGabriel et al. 1994). Morphologicaily it ha some chimpanzee features , e.g. the first molar and lower face, but others are hominid and show characteristics in common with A. afarensis - the skull more centrally placed on the vertebral column and the canine tooth half way between that of a chimp and of A. afarensis. Did A. ramidus walk on two feet, or was it a knuckle-walker (White et at. 1994)? Palaeontologists and geneticists agree that the split between ape and human lineages took place between five and six million years ago. In fact, one molecular estimate some fifteen years ago (Sarich & Wilson 1967), was 4,4 million years. Unfortunately there are no ape fossils that are younger than the Late Miocene. We need to find them to compare the parallel evolution of ape and hominid phyiqenies in palaeo-ecological contexts, in order to understand the selective adaptations both have undergone and to show which of the ape lineages and behavioural adaptations is closest to ourselves.
In August 1995 Maeve Leakey and her associates announced another major hominid find, from Pliocene sediments dated between 3,9-4,2 mya from Kanapoi and Allia Bay, in the Lake Turkana basin of northern Kenya. These finds consist of a mandible, cranial, daval and post-cranial remains, including a tibia, that are comidered on morphological grounds to be possibly ancestral to A. afarensis and perhaps a sister species to Ardipithecus ramidus (Leakey et at. 1995). The habitat was dry and wooded. These finds emphasise the need for more complete fossil remains and the definitive report on the Ardipithecus individual will do much to clarify understanding of the earliest stages of human evolution. There will be much speculation to whether several lineages of bipedal hominids existed more than four million years ago, of which only one was ancestral to our own lineage. If the split with the chimpanzee line took place between four and five million years ago then Ardipithecus lies close to the separation point; if this species was indeed bipedal, speciation might be expected to take place later rather than at the base of the root.Early hominid foot bones are now also reported from Member 2 at Sterkfontein, South Africa, and are believed to date to c. 3,5 mya. Four articulated foot bones from heel to big toe suggest that while the animal was fully bipedal, its divergent big toe is an indication of tree-climbing ability (Clarke & Tobias 1995). Again, debate is expected and there are some who, while agreeing that the bones probably belong to an early member of Australopithecus, would query the way the bones have been articulated by the authors.
The discovery of a late Pliocene hominid mandible ascribed to H. rudolfensis (African Homo erectus) from sediments at Uraha Hill, northern Malawi, dated to 2,4 mya is especially welcome since it comes from the one region to provide a link between the Plio-Pleistocene faunas of East and South Africa (Schrenk et at. 1993).
Fossils of Australopithecus afarensis and the later gracile and robust forms, including partial skeletons such as ‘Lucy’, are comparatively well-known. Recently, a more or less complete male cranium with face and mandible of A. afarensis and a partial female cranium have been found at Hadar where this species dates between c. 3,5 and 3,2 mya (Kimbel et al. 1994). The australopithecines were fully bipedal, as the famous footprints from Laetoli in Tanzania show, and must have used a variety of tools since their hands were adapted to this. They did not, however, flake stone for tools. That they could have done so is, perhaps, shown by the pygmy chimpanzee or bonobo, Kauzi, who developed the technique of throwing a cobble on a hard floor to remove a flake. Kanzi, however, showed no understanding of intentional stone technology. These, and others, are very significant studies of ape capabilities and intellect and show that the australopithecines with their larger brains must have been capable of even more dexterity and ingenuity (Toth et at. 1993).
Throughout human evolution and prehistory the environmental context is all-important for understanding behaviour and adaptation. A. ramidus is associated with forest, but with more open savannah close by. A. afarensis belongs in lakeside and fluvial habitats with a forest savannah mosaic habitat (Brain 1981; Vrba 1985).
By 2,5 mya, in response to Arctic ice sheet formation, global cooling and drying set in that brought about major adaptive dchanges in diet and behaviour. This is clearly seen in East Africa and Ethiopia and it is at this time that the first intentionally flaked stone tools make their appearance (Hark 1963).
The tools were simple core choppers and flakes (called Oldowan), useful for a range of tasks. The associated hominid grade, Homo habilis, as it has been called, is also unique to Africa but there is much discussion as to whether more than one taxon is represented by the fossil remains because of the variability in brain and body size. A case ha recently been made for two temporally successive species, ancestral to early and later Homo erectus (Wood 1992).
Homo habilis is, indeed, a mixed bag and there may have been several contemporaneous forms at this time - one of those periods of punctuated equilibrium and more rapid biological and behavioural readjustment and change. All these hominids were probably australopithecines, albeight advanced, and at least one with an enlarged brain is contemporary with stone tool making which is thought to have come about because of the need for a sharp knife to process meat, and greatly increased protein consumption. This represents the earliest recognisable record of a feed-back relationship between the brain and technology.
All the australopithecines (including the robust forms) and Homo habilis were relatively small, and the first large species appears, somewhat abruptly it would seem, some 1,8 mya. This grade is called Homo erectus and was found first in southeast Asia, then in China, but no firm means of dating was then available. In the 1970s and later H. erectus fossils were found in East Africa where they are all well dated to 1,8 to 1,6 mya in the Lake Turkana basin (Brown et at. 1985). These fossils are not as specialised as their Far Eastern counterparts and are said to show traits more like those of H. sapiens.
In Africa, the appearance of H. erectus is more or less contemporaneous with that of the Acheulean techno-complex with its bifaces - the first large standardised stone tools (handaxes and cleavers) a well as a continuation of the earlier chopper/flake tradition. The Acheulean at Olduvai Gorge is dated between 1,5 mya (EF-HR in Bed II) and 0,4 mya for the Acheulean in the Masek Beds over Bed IV (Asfaw aet al. 1992; Hay 1994). At Konso-Gardula in the southern Main Ethiopian Rift the sediments span the time 1,9-1,3 mya and contain rich assemblages of Acheulean bifaces and remains of early Homo (Asfaw et al.1992). Excavations at Bouri in the Middle Awash region of the Afar Rift yielded numerous occurrences of Acheulean dated to 1,1 to 1,0 mya. All these are early Acheulean assemblages but the Acheulean in Africa, as elsewhere, continued up to 200 000 to 100 000 years ago, when the bifaces disappeared and the flake-tool component evolved into the regional variants of the Middle Stone Age/Middle Palaeolithic. During its million years of evolution in Africa, the Acheulean spread into most habitats other than moist, evergreen forest and true desert.
There is now general agreement that the hominid lineage evolved in Africa. Until recently, it was thought that about 1 mya Homo erectus, taking along the biface (Acheulean) and the core/chopper/flake (0ldowan) technologies, moved out of Africa into Eurasia: first into the tropics and temperate region of southeast Asia and the Far East and later into Europe. This time-scale now has to be revised. The earliest Acheulean and core/flake tradition outside Africa (‘Ubeidiya in Israel) dates, on faunal, to c. 1,2 mya (Tchernov 1987). A Homo erectus mandible from Georgia and associated ‘chopper/flake’ artefacts with fauna is estimated to be perhaps 1,5 my old or more (Gabunia & Vekia 1995). In 1994 new radiometric dazes were obtained for pumice from the sediments from which it is believed that the Javanese H. erectus fossils came. These new dates are between 1,8 mya (Modjokerto) and 1,0-0,8 mya from Sangiran (Swisher et at. 1994). Provenance is sometimes uncertain and some of these fossils were found in the 1930s but, if the new pumice dates also date the fossils, then H. erectus appears to have been more or less contemporary in both Africa and Asia.
Dispersal into Europe appears to have bean somewhat later since no hominid fossils unequivocally ascribed to H. erectus have yet been found there, and stones claimed to be artefacts are either uncertain candidates or more recent than about 500 000 years ago. The earliest hominid fossils in Europe are generally assigned to archaic forms of Homo sapiens since they show sapiens features, in particular the expanded brain case. However, excavations at the Gran Dolina (U)) site at the new and very important locality of Atapuerca near Burgos in northern Spain have yielded a hominid frontal, other cranial and post-cranial fragments and so are more than 780 000 years old. As yet, specific attribution has not been attempted until further remains are recovered. In the same sediments are core and flake artefacts in quartzite and flint. These, with the hominids show that western Europe was settled at least by the late Early Pleistocene (Carbonell a at. 1995). Also from southern Italy there is now another possible Neanderthal ancestor reported sealed in a travertine matrix at Altamura (Dorozynsici l993).
From Boxgrove in southern England a hominid tibia shaft has been recovered, associated with butchered remains and Acheulcan bifaces and flake tools. Faunal associations suggest Boxgwve is between 524-478 kya. This has, however, been questioned and a younger age of 400 kya proposed. It is to be hoped that the new excavations at Boxgrove will uncover further hominid remains (Bowen & Sykes 1994; Roberts et al. 1994).
Archaic Homo sapiens fossils seem to make their first appearance in Africa (Brauer 1992). They are also found in China where the oldest H. erectus remains are c. 1 mya or younger, and the archaic sapiens forms, such as Jinnushan and Dali, are unlikely to be older than 500 000 (Schick & Zhuan 1993). Dating is the major problem with all these fossils since the methods available for the time range between about a million and 40 000 years have still to be refined and can give widely differing estimates of age, even in the case of the best techniques, uranium series and thermolumincsence dating (Aitken et al. 1992).
The biological changes from H. erectus to archaic H. sapiens were gradual but slow. When we examine the cultural associations of late Lower and Middle Pleistocene fossils, i.e. between c. 800 000 and 250 000 years ago, we can see very little change from what went before except at the end of this period, when there is more refinement in technology, a greater range of retouched forms and more symmetry. The Acheulean biface tradition, and also the chopper/flake tradition, lasted for a million years without undergoing much technological evolution. Change is there, ingenuity in flake production is there, but it is all much the same from one part of the Old World to the other. The Acheulean is regionally restricted, mostly to southern climates and environments. The chopper/flake tradition only is found from central and eastern Europe, across central - Asia to the Far East and southeast Asia. When we remember that the biface and chopper/flake components/traditions are indivisible parts of Middle Pleistocene cultural assemblages in Africa and southwestern Eurasia, how can this dichotomy be explained (Schick 1994)?
There are a range of possibilities but, as more and more data become available, the relationship between climate change and technological adaptations to environmental change becomes apparent and can best be explained, in the main, in terms of functional adaptation. The biface component is dominant and persists in association with a habitat centred on southern, more wooded terrain, while the chopper/flake component alone is present in colder and more temperate, probably drier and steppe-like regions north of the main mountain systems in Asia. The Acheulean bifaces do not penetrate north of this mountain barrier or east of the tropical evergreen forest in southeast Asia (Clark 1992). The precise behaviour patterning in both these major regions of the Old World remains to be identified and defined but out thing is certain, namely that the small isolated pepulsions were all doing much the same things for many thousands of years. Bifaces in Africa, Europe, India or the Levant are likely to have been employed in much the same way. The same is true of the chopper/flake assemblages. The resources exploited differed greatly, but all were processed in much the same way. There is no evidence at present for any regional variability that cannot be explained in terms of raw material.
Maybe the explanation is to be found in the fossil record. The unique skeleton of a Homo erectus boy from West Turkana, dated to 1,6 to 1,8 mya, shows that physiologically this hominid grade was different from ourselves although the overall similarity is striking (Walker & Leakey 1993). Homo erectus individuals were more robust than we are, but had smaller brains and narrower birth canals. Did they have language? Despite claims to the contrary, endocranial casts do not provide unequivocal evidence for language and nor does cerebral asymmetry. The vertebrae show that the spinal column was much like ours, but for one important feature - the spinal canal was narrower in the thoracic region so that they did not have as much grey matter or enlarged spinal nerves as we do and this is a feature believed to be connected with speech. The rib cage also indicated that H. erectus did not have the same respiratory expansion as we do - again a feature thought to be connected with the ability to speak. The best evidence for speech lies, I believe, in the archaeological record, and is shown by levels of technical complexity and symbolic representation. There is no indication of thismitation of this in the stone tools associated with H. trains. The general ‘sameness’ of the assemblages, wherever they are, is striking.
Before looking at early modern fossils and culture, this is a good place to see what genetics can tell us about the origins of our own species: Homo sapiens sapiens. There are two main hypotheses for the origin of modern humans, which have been labelled the ‘candelabrum’ and the ‘Noah’s ark’ hypotheses.
The first, the multiregional model, sees the present races steadily evolving over a long time from the antecedent, archaic populations in the areas where the present races are historically found. If so, then the racial characteristics of modern chinese, for example, come from Pekin Man (0,5 mya) and those of modern Europeans from Neanderthalers (100-30 kya) and the earlier archaic Homo sapiens stock. The unity of the modern human species is attributed to gene flow among contemporary populations.
The 'Noah's ark' or 'Out of Africa' model proposes that a radically undifferentiated stock of modern humans evolved in Africa and spread throughout the world, with the racial characteristics developing subsequently. This model emphasises that racial differences are relatively recent: they post-date the movement of modern humans out of Africa to replace all other hominids without interbreeding with them (Fagan 1990). This model was first put forward in 1987 by the late Alan Wilson and his colleagues (Cann et al. 1987) at Berkeley using mitochondrial DNA, as well as by Oxford (Wainscoat et al. 1986) and Stanford (Cavalli-Sforza et al. 1988) geneticists using nuclear DNA. While nuclear DNA seems to show Africans represent the ancestral modern humans, it says nothing about when these first appeared. Nuclear DNA is inherited from both parents, but mitochondrial DNA comes only from the mother. Mutations in mitochondrial DNA occur more frequently than in nuclear, so that nxitochondriai DNA is easier to trace trough time, using it as a molecular clock that can assign a date to every branching point on the genealogical tree. The clock assumes that genetic similarities organisms are a function of their relatedness and proportional to their divergence from a common ancestor; also that mutations take place at a constant rate. Various other factors need to be taken into consideration, in particular that the lineages have not mixed significantly. Calibration of such a molecular clock takes as a starting point the separation of the hominid and chimpanzee lineages c. 5 mya.
The first statistical calculations indicated an origin for modem humans in Africa at 200 kya (Cann et al. 1987). More recent re-calibration has suggested a date between 133 kya and 137 kya for the ‘African Eve’ (Stoneking et al. 1992), but some very cogent criticism from other geneticists has emerged. This calls into question the method whereby the calculations for the mitochondrial DNA clock are made. As one commentator says, “there is now a statistical cloud over the African Eden" (Templeton 1992:737).
So it is a question of returning to the drawing board and this is being done in a number of labs. Again, results from many thousands of family trees show the human populations in Africa exhibit the greatest variability in polymorphism of mitochondrial DNA (as nuclear DNA has always done) - and so have the longest history. Notwithstanding, claims are made for an ancestral home in Eurasia, the Levant or central Asia (Mann in press). Recalculation, using refined methodology, of the time that the modern human genome made its first appearance is now giving dates ranging from 160 - 112 kya, with indications that they are increasingly more recent. There continues, therefore, to be a strong possibility that some region in the continent south of the Sahara was the nuclear centre where anatomically modern humans first made their appearance (AAAS Report 1995).
If we can rely on the dates, at 100 kya there were anatomically modern humans in Africa and the Levant, and this is well demonstrated by the fossils. These are robust but fully modern, with no Neanderthal features. culturally they are associated with a Middle Palaeolithic/Middle Stone Age technology in both Africa and the Levant. Klasies River Mouth and Border Cave in South Africa, Dar-es-Soltan in Morocco and Qafseh and Skhul Caves in the Near East show this cultural association best (Beaumont et al. 1978; Clark & williamson 1984; Debenath et al. 1986; Bar-Yosef 1989; Deacon 1992).
There is nodoubt that the African Middle Stone Age was the direct descendant of the Acheulean, the bifaces having mostly disappeared and the prepared core technology being more refined. This is the first time that regional cultural variability can be seen (Clark 1992: fig. 1). Where raw material permitted, there was a strong emphasis on blade production. The Middle Palaeolithic/Middie Stone Age covered the time c. 130-40 kya and regional variant can be seen to have undergone change within the basic technological system. The same is the case in the Levant, the Indian sub-continent, central Asia and the Ear East. The antecedent lithic tradition in the last two regions was the core/flake complex. In the Levant, the Middle Palaeolithic is associated with both modern and Neanderthal fossils. In Europe, the classic Mousterian traditions are well known but here the physical type was Neanderthal. So stone tool technology is largely independent of physical type and is, at this time, a manifestation of a way of life in which behavioural patterns cannot have varied all that much and social organiation and resource use were broadly similar. The antecedent hominid fossils from Africa - from H. rhodesiensis, Bodo and Sadanha through Ngaloba, Ndutu and Jebel Irhoud - are well known, as are heir contemporaries Petralona, Swanscombe, Steinhem and l'Arago from Europe (Klein 1989: 224-262). Major discoveries continue to be made at Atapuerca, a karstic cave system in northern Spain (Arsuaga et al. 1993). Here a pre-neanderthal population is being recovered, including males, females and children, comprising fragmentary but complete skeletons (Nieves & Mendoza 1993). They date, on latest estimates, to between 150 and 130 kya (J. Bischoff pers comm.). They are not Neanderthal, but show some incipient Neanderthal features, although post-cranial skeletons suggest a more tropical origin for these ancestors of the European Neanderthals. The contemporary stone assemblages are thought to comprise bifaces, ‘choppers’ and flake forms: namely, to be a Late Acheulean.
If the modem human genome evolved in Africa and spread into Eurasia, what might the catalyst and contributory causes have been? Climate, again, was surely a major influence. The great advances that have been made recently in interpreting deep sea cores and the cores trough the Greenland and Antarctic ice cores show the complexity and severity of some of the changes over the past 200 000 years that can be shown, or at believed to be a significant cause of population movement and technological change (Van Campo et al. 1982; Peel 1992; Jouzel et al. 1993; Bender et al. 1994).
In Africa, the key region controlling the movement and interaction north and south is the Sahara (Clark 1992: fig. 2). hypothetical vegetation maps for an interglacial and glacial suggest interglacial conditions were somwhat warmer and and wetter than today and the glacial colder and drier. during interglacials the Sahara was occupied and north and south movements took place. during glacials, the desert was hyperarid and unoccupied.
The Last Interglacial saw the first use of seafoods and the grinding of plant foods (Clark 1992: 206). Population increase can be predicted and expansion into and interaction with the populations of the LEvant. At the maximum of the Last Glacial the Sahara was unoccupied and at times sea-level was more than 100 metres lower than today (Clark 1989).
The Middle Palaeolithic population in North Africa north of the desert during the Last Glacial have received an influx of population from the south and further interaction between the Levant and northeast Africa must have resulted. A similar situation can be predicted for the earlier penultimate glacial. But in central Asia and the Far East, while cultural changes are documented, the chronology needs to be established.
What can be said of the Middle Palaeolithic/Middle Stone Age way of life, whether modern or Neanderthal, based on the archaeological residues at occupation sites? Groupings were probably larger but broke up seasonally into smaller groups, leaving the home bases for foraging and other special purpose camps. Repeated use of home bases such as caves and rock shelters (and even some open sites such a El Guettar Tunisia) is clearly seen. Social relationships were more closely organised but band composition within kinship relationships may have been regularly changing. Technological innovations such as blade production, segments and tanged or basal reduction tools are clear evidence for hafting and the invention of the first simple composite pieces of equipment. People remained efficient scavengers of carcasses as well as hunters of large game, probably by group driving (Clark 1989).
They were the first to make use of seafood, as seen from South Africa and Cyrenaica. They made use of pigments: red ocbre and specularite, and sometimes they buried their deal. This speaks of the beginnings of self-awareness and use of symbols but symbolic expression does not ‘expand’ until some 45000 years ago, give or take a few thousand. Why, if the chronology is correct, did it take modem humans some 50 000 years to develop full cultural awareness, while Neanderthals remained largely as they always had been? Until more of the hard data are available in chronological context, it is possible only to conjecture why it was that between 50 000 and 40 000 years ago the complexity of Upper Palaeolithic culture evolved, relatively suddenly, and spread so rapidly throughout the Old World.
There is every reason to accept that anatomically modern humans could have evolved in Africa at the time suggested by the molecular record, but it seems that they had not yet acquired the unique intellectual abilities that made possible the complex social organisation and symbolic behaviour associated with Upper Palaeolithic populations. The catalyst that made the Upper Palaeolithic possible was, it has been suggested, the development of a full language system like our own which opens up a new world of ever-broadening horizons and opportunities; the ability to convey specific information, to distinguish between past, present and future, to think abstractly, to use symbolism and, in short, to be psychologically similar to ourselves (Barber & Peters 1992). The threshold must be in that time range when Middle Palaeolithic technology was replaced by the Upper Palaeolithic, the cultural complexity of which is seen in the circumstantial evidence of activity areas, settlements, in the proliferation of technological variability and change and in elaborate artistic expression.
Whether the ability to speak is a physiological or neurological phenomenon, or both, is for the anatomists and linguists to decide. It has been suggested that the neural structure of the brain could have allowed early hominids to have a so-called ‘primitive’ language with a vocabulary of words signifying meaning but lacking the grammatical elements of syntax (Bickerton 1981:164-197). We can see the jump from ‘primitive’ to syntactic language as rapid and consider that it emerged as a single genetic event. But, if the first anatomically modern humans already had a syntactic language system, why do we not see this most significant development reflected in the cultural evidence associated with the early modern fossils? If, towever, they were neurologically pre-adapted and full language developed only later and suddenly, so that there were two genetic events rather than one, this would account for the lag in the cultural revolution represented by the Upper Palaeolithic traditions and the very rapid spread of the modem human genome from 40 000 years onwards. Can this spread best be accounted for by the multi-regional model or the monogenesis one? The latter seems the most likely and in this connection it is of interest then why modern fossils from eastern Asia and Europe are closer morphologically to each other than are the modern fossils from eastern Asia to the antecedent hominid fossils of the region. This suggests the migration hypothesis, though some gene flow between populations seem to be observable. The most convincing evidence for replacement is that of European Neanderthal populations by Cro-Magnon people with the Aurignacian industry, between 40 000 and 30 000 years ago.
The first humans to enter Australasia, perhaps more than 40 000 to 60 000 years ago (Allen 1994; Roberts et aL. 1994), were anatomically fully modem and carried with them a tool-kit resembling that which had been in use in China since the days of Homo erectus. If, however, there is no compelling evidence for the direct descendence of the modern mongoloid and australoi populations of eastern Asia and Australasia from pre-existing gene pools in the east, it is equally possible that modem humans pushing eastwards were quick to readapt their technology and behaviour to patterns best suited for exploiting the resources of the new regions into which they moved.
The last three years have seen major discoveries of very early hominid fossils. After additional and more complete remains have been recovered from these sites, and have been fully described, these will show whether the hominid root stock was monophyletic or whether there were several radiations that later became extinct. A systematic search for dateable early hominid fossils from Europe and Asia is particularly important, to show whether an australopithecine grade might have been present in Eurasia as well as in Africa; at present no such evidence has been found. Of special interest also is the need for more precise dating of the initial hominid migration out of Africa since it is now clear that this took place earlier than previously thought. The Georgia fossil is perhaps more than a million years old, and the Gran Dolinia hominid fossils open up the possibility of a second route of entry into Europe from north-west Africa into southern Spain.
To summarise the data and hypotheses presented here: the nuclear DNA, pahacontological and archaeological evidence point to an early emergence of anatomically modem humans in Africa from perhaps 200 000 years ago. By 100 000, modern groups had spread into western Asia where they lived for some 50 000 years contemporaneously with Neanderthals. While it is to be expected that behavioural adaptations of modem humans and Neanderthals grew increasingly different, this does not appear to be reflected in the cultural associations although meaningful variation may, perhaps, be obscured by the too generalised level of the approach we are using. Ssome time subsequent to the move into the Levant (and po~ further afield), the modem human genotype developed a syntactic language system that, by 40 000 years, had revolutionised social organisation, communication and symbolic relationships. As they moved through Eurasia, bearers of this modern gene pool received no significant genetic input from the archaic human races they encountered and replaced in their population of the world. If this scenario is confirmed it would seem that our own species is really very young and spans only 10 000 generations. This is not a long time, but sufficient for the many ethnic and linguistic adaptations to have evolved; it shows the close relationship that exists between the races of our world.