by Paul Jordan
The life of Homo habilis was still a simple one, with no unambiguous evidence of home bases with any sort of built structures or the use of fire. Much food no doubt came as ever in the form of vegetable matter but it seems clear that habilis was extending the business of procuring and processing meat beyond anything seen among today’s chimps or the Australopithecines. In the nature of things, it is difficult to know whether just scavenging or some resort to hunting accounts for the collection of meat-bearing animal bones (of pigs, antelope, horses, even elephant, hippo and rhino, and some carnivores) found in association with Oldowan tools. It certainly looks as though cuts of meat on the bone were being brought away from kill-sites to be cut up and consumed by habilis groups, but whether habilis or predatory animals were doing the initial killing is not so clear; the occurrence of lower limb bones and skulls, typically left over by carnivores, suggests that habilis scavenging was more to the fore than hunting, especially where larger prey was concerned. Cut marks on the bones do establish that the Oldowan tool kit was being used to process the meat, but the marks of carnivore teeth indicate that at some stage, either before or after habilis got at them, the bones also received the attentions of predatory animals. If habilis was scavenging after carnivore kills, he was at least a top scavenger on the strength of the animal bones he left among his tool debris and the marks he made on those bones. The situation was probably very like the savanna scene today, with clusters of bones building up in the shade of trees where various carnivores from time to time consume meat they acquire by hunting or scavenging – only in those remote times, habilis was one of the hunters or scavengers (on rather a grand scale, it seems at Olduvai) and he perhaps kept his tools handy on the spot to help deal with any meat that came his way. Sharp-edged flakes would have served to cut up meat and the heavier core tools would have facilitated the breaking of bones for marrow. Meat eating provided more energy more readily and economically than a vegetarian diet could ever do and it has been ingeniously proposed that it went hand in hand with brain enlargement; to preserve the metabolic balance overall, as the energy-demanding brain expanded with evolution, the gut could be usefully reduced in size through the eating of energy-rich meat. On this proposal, meat eating was the sine qua non of brain development, upon which natural selection set such a premium for the sake of cleverness in social behaviour and resourcefulness in survival and reproduction.
The complex interaction of brain development, ground-living, bipedalism, toolmaking, meat eating, social and sexual relationships, all at the mercy of natural selection, cannot be underestimated as the motor of anthropogenesis, the process of becoming human. Once a formerly arboreal and largely vegetarian line of ex-apes embarked on a bipedal, open living, group structured, toolmaking and meat eating way of life, there was no going back on cleverness unless it be to extinction. Even scavenging from carnivore rivals, to say nothing of hunting, required organization and social skills to a high degree and reliance on animal food, however acquired, called for cleverness well beyond that required for a steady diet of vegetation; meat could only be had from mobile, changeable, tricky and frequently dangerous sources, in competition with creatures fiercer and in some ways more cunning than early Homo himself. (Predator animals tend in general to be bigger-brained than prey animals.) Getting meat demanded powers of observation and interpretation, together with memory and communication of information, and socially coordinated action, that had not been seen in the hominid world before. Habilis and his descendants simply had to be clever to survive and prosper, and enlargement of the neocortical part of the brain was the mechanism to afford that cleverness, extending mental acuity forged in the social context to more and more aspects of life. The ratio of neocortex to total brain size among the primates goes roughly hand in hand with group size; cleverer primates can successfully associate in larger social groupings and it has been estimated that a habilis individual might have had social knowledge of up to about eighty other individuals in his band. Larger bands meant greater security in numbers and greater scope for organized food procurement. It may be that the beginnings of a sort of family life were made during the habilis era, with males cooperating in the search for meat, some at least of which they shared with females and offspring back at whatever in the way of ‘home’ they could be said to have had. Bipedalism would have made it easier for the hunters or scavengers to forage quite widely in their environment and raw meat makes a package of food energy that is easy to transport back ‘home’ at the end of the foraging day, along with tools or the raw material for making them.
Among modern foraging (hunter/gatherer) peoples, meat is eaten in as great a quantity as it can be got and is the very stuff of food sharing, both with fellows in the foraging group and with wives and children back at base. It has to be shared by presently successful hunters with the less successful for the moment, against the day when fortunes are reversed. At home, meat succours the women and children whose plant foraging is necessarily limited by the rest of the demands of life upon them; meat sharing promotes more or less monogamous relations and family life. If such distinctively human arrangements as these were beginning to evolve in habilis groups, then it may equally well be that the human phenomenon of long postnatal maturation of the young was initiated, if only faintly at first, at about the same time, with its drawn-out period of maternal care and its slow but extensive growth of the brain after birth. Postnatal brain growth is closely related to human infants’ capacity to learn so much and go on learning. We have seen that, even as late on as Neanderthal times (one-and-a-half million years later than the last of habilis), the evidence of infants’ fossils indicates a rapider maturation than is seen with the children of Homo sapiens sapiens, but for all that the big-brained Neanderthalers were born with large heads like ourselves through birth canals big enough to accommodate them. Australopithecine pelvic arrangements, on the other hand, though adapted for bipedalism, were more ape-like in respect of birth canal dimensions and Australopithecine infants were not big-brained at birth, nor destined to go on to be very much bigger-brained than chimpanzees when they grew up. The small Australopithecine child from Taung in South Africa was only, according to details of the teeth, about three years old but already displayed features suggesting to its discoverers that it was, in modern human terms, some six years old. Somewhere between the Australopithecines and Homo erectus/ergaster, presumably in the times of Homo habilis, modern patterns of gestation and brain development before and after birth were begun.
Homo habilis (right) with ‘1470’, which may represent another related but more evolved species.
The remains assigned to Homo habilis exhibit a range of variability that leads some anthropologists to question their being lumped together into one species. There are marked size differences that may be attributable to more than sexual dimorphism. Some exhibit features that foreshadow, more than those of the others, the physical characteristics of the next stage of human evolution, that of Homo erectus and Homo ergaster, with marked brow-ridges and a more angular shape to the back of the skull, a new prominence to the nose (away from the ape-like flattened formation of earlier hominids), and a face more tucked in under the vault of the skull. The postcranial skeletons of various representatives of Homo habilis also vary considerably, with some individuals still displaying the short-legged, long-armed configuration that goes back to the Australopithecines, while others have the longer-legged anatomy of erectus and ergaster.
Homo habilis fades out of the fossil record at around 1.8 mya, at which time the next stage of human descent is in evidence in Africa, and – according to some evidence – in other parts of the world, too. The robust Australopithecines of Africa did not quit the scene with the departure of habilis and the appearance of his successor, but we can practically say ‘goodbye’ to them too at this point, though they may have persisted in places until as late as 1 mya or even later. They had evolved into an adaptation to a specialized ecological niche on the savanna which saw their ultimate
extinction after a long (and therefore successful) career. Whether they ever made stone tools cannot be yet answered with certainty; their remains are sometimes found in association with Oldowan artefacts, as are those of habilis, the reliably presumed maker of those tools. The conclusion that the robusts in these circumstances were accidental intruders on the scene or victims of habilis is strengthened by the fact that, after the disappearance of habilis and, for the most part, the Oldowan culture, the robusts who remained at later dates are not found in further association with Oldowan-type tools.
The later stages of the Oldowan tool tradition show features that prefigure the Acheulian hand-axe cultures of Africa and the wider world. Hand-axes are bifacially worked tools, rather than crudely shaped pebbles with only a few flakes removed from them. The later Oldowan includes bifacially worked pieces on their way to Acheulian axes. Properly bifacial artefacts begin to appear in the African archaeological record at about 1.5 mya. The development of the standardized all-purpose hand-axe tool surely points to the related development of enhanced mental powers among the habilis populations transitional to Homo erectus or Homo ergaster, who appeared at much the same time as the toolmaking changes occurred. We can reasonably infer that the slow progress of language saw significant developments along with the tool improvements and the anatomical changes associated with the evolution of the erectus/ergaster species. The more highly patterned nature of hand-axe production, involving more steps in the making and better previsioning of the finished product for general-purpose use, is likely to have been mirrored in a more structured, standardized and extended use of language.
Some anthropologists see among the various representatives around the world of the stage of Homo evolution after habilis only a single if variable species called, after the species name conceived so long ago by Haeckel and taken up by Dubois in Java after him, Homo erectus. Others believe that an African expression of this post-habilis stage of human evolution was so significantly different from erectus as discovered in Java and China as to merit a species name in its own right – ergaster. (‘Erectus’ was meant to draw attention to the full achievement of un-ape-like posture, ‘habilis’ to handiness with tools and ‘ergaster’ to the capacity for useful labour.) In recognition of the possibility of a real distinction between the African and Asian species, at the same time as noting their essential similarity at a stage of human evolution, we shall sometimes use the slightly awkward formula erectus/ergaster (or vice versa) to refer to the fossils that take on the story of human descent from H. habilis to H. sapiens. (It has to be said that on the same principle, we might as well refer to a very much later stage of human evolution by way of neanderthalensis/sapiens.)
It used to be assumed that the transition from habilis to erectus was effected solely in Africa, to the accompaniment of the development of the Acheulian out of the Oldowan, with a subsequent spread out of Africa by way of the Jordan Valley, which is an extension of the East African Rift Valley. This view retains much force, especially in the light of the continued absence of anything like habilis fossils outside of Africa. But with tools, it might be a different story. There are claims for Oldowan type tools (if they are tools at all) in Pakistan back to 2 mya and in China to perhaps 1.8 mya; and early appearances of pebble tools in the Middle East and Europe are not unknown, though none in Europe is proved to reach back as far in time as the last of the Oldowan in Africa. If any Oldowan assemblages outside Africa really do date back as far as the Pakistan material is claimed to do, then the possibility arises that despite the absence of fossils, habilis or habilis-like creatures (though probably already evolving towards erectus) were at large in Asia, for example, at a time predating the evolution of ergaster/erectus in Africa as we know it from the fossil record there. On this view, the case for a real distinction between Asian erectus and African ergaster is strengthened, with separate but convergent evolution in the two areas leading, perhaps with some long-distance genetic interchange via neighbouring groups strung out along the way, to the evolution of erectus and ergaster as convergently similar but specifically different versions of Homo at much the same stage of human physical evolution. Controversial dates for new Homo erectus finds in Java at 1.8–1.6 mya and for an erectus tooth in China at 1.9 mya certainly seem at odds with the idea of ergaster/erectus origins solely in Africa, unless those origins extend somewhat further back into the past than presently available fossils indicate. Some anthropologists think that ergaster must have evolved in Africa (out of one of the habilis types) at an earlier date than the fossil record so far demonstrates, and that East Asian erectus is descended from this early African ergaster. At Dmanisi in Georgia, in association with a tool assemblage described as Oldowan, a jaw fragment was discovered dating to about 1.8 mya that is claimed to resemble African ergaster more than East Asian erectus. If the characterization of this fragment is correct and its date holds up, then a very early representative of Homo ergaster has been identified well out of Africa. The route taken by evolving humanity out of the continent of its origins is likely to have been through the Jordan Valley continuation of East Africa’s Great Rift Valley; both valleys enjoyed similar ecological conditions before the era of the ice ages began. At ’Ubeidiya in Israel a succession of Oldowan levels is topped by a Developed Oldowan that features some crude hand-axes at about 1.4 to 1.2 mya with some very fragmentary skull and teeth remains. Evolving humans, incidentally, were not the only creatures to make the journey out of Africa at this time – lions, leopards and hyenas took the same course.
It is interesting at this point to recall that no Acheulian tradition ever existed in many parts of the Far East, where altogether simpler and less patterned stone tools persist until late palaeolithic times; it is likely that the best part of the tool kit of these easterners was always based on long-term perishable materials like bamboo that have vanished from the archaeological record. Possibly the Acheulian idea never reached the Far East because its inventors and their descendants never went there either. The oldest archaeological material from China, in the form of stone tools, dates to some 1–0.75 mya, well after the African development of the Acheulian, but none of it is Acheulian in China, though finds of hand-axes have been claimed in Mongolia and Korea.
‘1470’.
In the absence of any habilis and late habilis material in the region, there are really no fossils whereby to trace any in situ evolution to erectus in Asia, which – while it does not prove that no such evolution took place there – has traditionally strengthened the impression that Asian erectus origins are ultimately to be traced back to Africa. It can be argued that some among the African habilis specimens we have, like the individual from Koobi Fora known as 1470 and dating to about 1.9 mya, were already on their way to an ergaster/erectus character well before the oldest clear-cut ergaster specimens we know. In particular, it has been said that brain casts of the large-brained (for the time) 1470 – at about 775 ml, way out of the range of any Australopithecine – show signs of the development of brain areas associated in ourselves with the generation and comprehension of speech. If the projection of these associations back into such representatives of our remote ancestry as 1470 is justified, then speech development is just what we might expect as one of the accomplishments of habilis on the way to ergaster/erectus. The high neocortical ratio of evolving habilis suggests enlarging group size and ever more complicated and demanding social relations, to be negotiated (‘groomed’) with ever subtler chatter. With speech, you can groom whole gaggles of people at a time, as politicians know so well, and be doing something else at the same time.
We have seen that some of the habilis specimens to hand have rather long arms in the tradition of Australopithecus afarensis (like Lucy) and smallish brain capacities, but the large-brained 1470 remains lack arm bones to tell us whether this primitive feature persisted among the larger habilis types (who may be so different from the others that they should really be assigned to a new species, as some anthropologists now propose). The true
ergaster/erectus remains from a couple of hundred thousand years or so later on do not display, where the relevant bones are available, the long-armed character of some of the habilis specimens. Several skull and jaw fragments of ergaster/erectus are known in Africa from about 1.75 mya but the most spectacular remains are those of the Nariokotome Boy of about 1.6 mya, much of whose postcranial skeleton is available for study and whose cranial capacity can, thanks to the state of preservation of his skull, be precisely determined: more than can be said for any other human fossil over 100,000 years old. Though a juvenile whose age is estimated at about eleven years (on the strength of his teeth characteristics), the Nariokotome Boy was already some 1.6 m tall, with a cranial capacity of about 880 ml – assuming a somewhat earlier age of maturation than is seen among modern people (and his skeleton as a whole suggests a fifteen-year-old, though his teeth tell a different tale), we may guess that he would have reached about 1.75 m in height and perhaps 900 ml of brain capacity at full adulthood. The modern human brain is about three times larger than we would expect for primates of our body size, so that – at 900 ml – Homo erectus at Nariokotome can be seen as well on the way to the modern ratio of brain to body size, and in fact brain size doubled between about 2.5 mya and 1 mya from something scarcely outside the ape range to a capacity only about one-third less than the brains of people today (and Neanderthalers). This increase in brain size can be seen as indicative of growing group sizes among the bands of our ergaster/erectus ancestors. It is the prefrontal cortex of the brain that has seen the greatest expansion in the course of human evolution, with some relative loss of capacity in brain areas associated with smell, sight and motor control in our monkey relations (who had to be able to leap about in the trees, after all). The areas of gain in evolving brain capacity are those plausibly thought to be associated with speech and conceptual thought. Interestingly, the larynx of ergaster/erectus appears to have fallen about midway between the positions seen in the Australopithecines and in modern humans, bolstering the supposition that speech and language were developing, however slowly, along with physical evolution. And another telling respect in which ergaster/erectus resembles modern people more than his predecessors resides in the details of the inner ear that have been preserved in some specimens. The modern sort of nasal opening is fully realized with ergaster/erectus, too, perhaps to help cool the burgeoning brain.
