The 1.5-million-year-old

The realisation that not each and every hominid fossil can be forced onto a single lineage leading inexorably to modern humans has forced palaeoanthropology to face up to the difficult task of reconstructing earlier ecologies, behaviours and adaptations for which there may very well be no modern counterparts. These two books, otherwise so different in scope, subject matter, treatment and intended readership, attempt this formidable challenge with conspicuous success.

The Wisdom of Bones is a popular account of the most complete early hominid ever recovered, the skeleton of a Homo erectus youth about 1.5 million years old from Nariokotome, Lake Turkana, discovered by Richard Leakey's team in 1984. Alan Walker is an anatomist of unrivalled experience, responsible for the preparation and reconstruction of just about every important hominid fossil recovered by the team. He is also an evolutionary biologist of exceptional flair: no one else could have identified rock hyraxes as an important source for studies of early hominid diet. Pat Shipman is a palaeoanthropologist and accomplished science writer. It is difficult to imagine authors better equipped to convey the significance of the "Turkana Boy" to a wide audience. And the account makes strikingly clear just how significant he is.

The first chapters describe the specimen's recovery, and outline the background of earlier fossil finds, from Java through China to the important African discoveries of habilis and erectus by the Leakeys and others; the second part of the book focuses on the Turkana youth and reviews various aspects of his biology. The boy was about ten years old at death - because of his more rapid maturation, comparable to a modern lad's early-to-mid teens. At about five foot four he was tall for his age, of linear build, long-limbed and strongly muscled. He contrasts with hominids such as Australopithecus and H. habilis, who were shorter overall, deep-chested and pot-bellied, with short legs and long, powerfully muscled arms suggesting appreciable arboreal activity. Turkana Boy's pelvis and leg anatomy are essentially modern, pointing to striding bipedalism with no hint of climbing adaptations, so indicating a fully terrestrial niche when habilis and other forms combined a different ground bipedalism with tree climbing. Moreover, the skeleton's limb proportions and linearity most closely resemble modern people living in hot, dry, open environments. Whereas earlier hominids were all tied to varying extents to treed locales, from H. erectus onwards body form, limb proportions and bipedalism can all be seen as components of an adaptive complex allowing strenuous terrestrial activity in hot, open habitats.

This habitat change is associated with shifts in dietary niche and developmental processes: the boy's cranial capacity was around 900cm - average for early H. erectus. Reconstruction of a female pelvis, based partly on this specimen supplemented by other material, shows that the human characteristic of "secondary altriciality" - prolongation of brain growth after birth, in contrast to other primates - had already evolved by the time of early erectus and perhaps even habilis. Extended brain growth requires a secure source of high-quality protein for the lactating mother and weaned infant, leading to a shift from plant-eating to carnivory and so hunting, facilitated by more complex social bonds. Estimated gut size, assessed from the trunk proportions and linearity, accords with increased meat eating, while greater sociality and carnivory are also indicated by another erectus from Turkana. The 1808 female partial skeleton shows spectacular pathological thickening of the limb bones, most likely due to poisoning by excess vitamin A from eating carnivore liver - soft, and therefore easily ingested. So initial, inexpert carnivory led to an extremely painful, immobilising and ultimately fatal affliction for 1808, during which she would have needed assistance and provisioning from other erectus individuals.

If all this reads like the Whig interpretation of prehistory, Walker and Shipman offer two valuable correctives: they point out that Turkana Boy, with the maturity, size and build of a heavily muscled modern 15-year-old had a brain size comparable to a modern one-year-old, a discrepancy which implies radically different kinds of behaviour and cognition from modern humans. The second corrective is based on new evidence for brain functioning, particularly the neurological basis for speech. Broca's area, on the brain's lower-left frontal lobule, has traditionally been associated with speech production. A similar swelling has been identified on fossil endocasts from H. habilis onwards, and cited as evidence of early hominid language capability. Walker and Shipman present new evidence from studies of brain function that Broca's area is concerned with complex motor programming rather than language acquisition as such, and so its identification in fossil hominids, even if correct, provides no assurance of language capability. Moreover, Turkana boy had a narrow vertebral canal in the thoracic region, implying a spinal cord like nonhuman primates, rather than the wider cord of modern humans with its greater numbers of neuron bodies (grey matter), which innervate the chest and abdominal muscles, important for the fine control of breathing during vocalisation.

So there is no clear support for early language acquisition by erectus, and instead some evidence against. The overall picture of H. erectus is a hominid of essentially modern dietary niche, body size and proportions, powerfully built, with developmental patterns more extended than any nonhuman primate, and with suggestive evidence of complex socialisation, but without the fundamental language capability of modern humans. All this points to an adaptive niche distinctively different from ourselves or, indeed, any other modern species. Aspects of this picture can be seen, with hindsight, in previous erectus discoveries, but it took something as complete as the Turkana specimen, and Walker's biological insights, to piece the functional puzzle together. Turkana Boy is invaluable not just because he is so complete, but because he is so normal an erectus.

The Neanderthal Legacy considers behaviour almost one and a half million years and a continent away from Nariokotome. This is a detailed, scholarly review of the west European Mousterian complex of stone industries dating between about 150,000 and 30,000 years ago, and associated with Neanderthal Man. To many these flake assemblages appear scrappy and amorphous compared with the highly differentiated Upper Palaeolithic tool-kits, and the contrast has been widely argued to support the view of Neanderthals as less intelligent than early modern humans. In fact, there is considerable variation in Mousterian assemblages, and much archaeological effort has been directed towards its analysis and evaluation.

Virtually all researchers utilise the taxonomy of Francois Bordes who, on typological and technical grounds, identified five major Mousterian variants. Their significance, however, is much more debatable. Bordes conceived the variants as culturally determined, reflecting ethnic divisions among Neanderthals; an influential view, associated particularly with Lewis Binford, sees them as functional variants, while Mellars has long argued for temporal change as a major determinant of Mousterian variability. Others argue that much assemblage variation is not a designed end-product, but the fortuitous result of resharpening, and stages in flake reduction that happen to be frozen at a particular point in time. In the first half of the book Mellars reviews at length the Bordean scheme, technical and functional studies, raw material effects and temporal influences on assemblage composition. The account is both broad and detailed, and particularly valuable since generalisations are firmly tethered to specific site analyses and their empirical basis made accordingly clear. As a result, speculation and wishful thinking are conspicuously absent.

The later chapters treat broader behavioural aspects of subsistence, site location and internal organisation. Hunting large bovids, as opposed to opportunistic scavenging, is indicated at some sites, perhaps by driving them towards natural traps (avens or cliffs). Most west European sites are caves or rock shelters overlooking river valleys, close to sources of raw material, and near a variety of local habitats. Possible open sites are many but definition is difficult, and excavated open sites are few with organic preservation problematic, so hindering functional interpretation. However, there is some evidence to distinguish between larger, richer sites representing repeated occupation at higher, more exposed localities, and smaller, poorer sites at lower levels marking "one-off" activities, often involving tool production. Evidence for spatial organisation includes the distribution of tools and faunal remains, and the presence of hearths, cobbled paving, pits, post holes and (debatable) stone walls, without, however, the clear differentiation and complex internal organisation indicated at Upper Palaeolithic sites.

The concluding chapter briefly reviews relevant fossil and genetic evidence, but appropriately focuses on the archaeological record, and the major contrasts either side of the Middle-Upper Palaeolithic transition. Mellars sees these as reflecting a longish period of contact and coexistence before Aurignacian numbers increased to the point where Mousterians and local derivatives such as the Chatelperronian were marginalised to extinction. New tools, technologies and materials, larger more complex sites, extended distribution networks and accomplished art all indicate the incomers' competitive edge. While commendably cautious and balanced, aspects of this interpretive synthesis will inevitably be challenged. But however much they contest particular points, other workers cannot afford to ignore Mellars's authoritative account of Mousterian studies, which immediately ranks as a definitive survey.

Alan Bilsborough is professor of anthropology, University of Durham.