Converging on the ultimate

Giant brains, tool use, bipedality, and even a precision grip are not, therefore, specific to humans. To be sure, in our species they are each developed to a high order, but their independent emergence suggests that in principle there is no reason why they could not be similarly honed. Still, that does not rule out the possibility that the human lineage possesses unique features, which if lost by some chance would never be able to evolve again in the contingent turmoil of continuing evolution. The facts, however, point in precisely the opposite direction. When we peer into that 'bush' of hominid diversity (note 244), encompassing perhaps as many as seven species of Homo and a similar number of the more primitive australopithecines (including Australopithecus, Paranthropus, and Ardipithecus), and the more remote Sahelanthropus (and perhaps Orrorin), then a familiar tune is heard. Much has been made of this sprawling bush of hominid diversification from, among others, those anxious to demolish any sense of linearity in our history, especially if the implication is that this evolutionary trajectory might even be progressive. This discussion, however, misses the point. Recall that we are interested only in the emergence of particular biological properties: some will be of principal interest to a restricted group; for example, teeth to dentists. Others might be of universal interest; for example, intelligence. In either case, however, the convergences emerge.247

Concerning dentistry, one of the most spectacular examples involves an offshoot of the australopithecines. They are characterized by huge grinding teeth (appropriately called megadontic) and the associated development of a massive jaw musculature. This evolutionary excursion, into what is generally agreed to be serious vegetarianism, actually arose independently at least twice, and perhaps three times.248 These robust australopithecines are instructive because of what they tell about the realities of evolution and the rules of convergence. The first time these powerful teeth were developed (in Paranthropus aethiopicus) is correlated with a massive accentuation of two sets of jaw muscles, specifically depending on the deployment of the posterior temporalis and anterior masseter. On the second occasion when the robust habit emerged (in Paranthropus robustus and P. boisei), one of these muscles had already become reduced so that the grinding process largely depended on the action of the masseter muscle.

As Rob Foley249 noted, in reviewing this case of convergence, 'Clearly, in evolution there are more ways than one to crack a nut.' He then went on to remark that 'these anatomical differences [between the robust australopithecines] reflect alternative ways of solving the problems of heavy chewing, and which one evolved depended upon what had already happened in the lineage'.250 Quite so, yet Foley then concluded, 'More interesting though, is the whole issue of convergence.' It is to this topic that he returns in a short but stimulating chapter published in Structure and contingency.251 A central insight made by Foley, echoed frequently, but equally widely neglected, is his remark that 'Convergence is perhaps the strongest evidence for adaptation.'252 Foley is in no doubt that key features in hominid evolution, such as 'bipedalism or increased meat-eating, characteristics that underlay the hominid adaptive radiations, are adaptive, functional, and the product of natural selection.'253 He does not deny the roles of contingency and other stochastic factors - why should he? - but his concluding remarks are judicious and tally with what we know about the realities of evolution. Thus he writes, 'while contingency plays a part in the timing and location of evolutionary events, the way these events are played out, the final biological outcomes, are strongly influenced by selection, adaptation and function,' and he concludes, 'evolution is the outcome of both stochastic and deterministic processes. As such, should the tape of life be replayed, undoubtedly, there would be many differences, but there would also be a very significant number of similarities.'254

Hominids evolve, and unsurprisingly given its ubiquity, convergence is inevitable. The independent development of nut-cracking is a dramatic example, but there are also more subtle instances. In becoming more gracile and showing a reduction in tooth size our own species Homo sapiens marks a departure from the general hominid robustness and actually approaches once again the more primitive condition found in our pre-australopithecine ancestors. The differences between us and the australopithecines are, of course, much more obvious. In some ways the most significant is the general absence in the australopithecines of any evidence of a stone tool culture. The earliest such occurrences, the Oldowan Industrial Complex, are from Gona in Ethiopia and are dated at about 2.5 Ma.255 An array of slightly younger (c. 2.3 Ma) tools from Kenya256 is important because reassembly of the fragments (cores and flakes) shows that tool-preparation involved a high degree of dexterity. Although most are evidently the product of early Homo it is almost certain that the late-stage australopithecines, including Paranthropus, were also tool-makers.257

Most probably the nascent skill in tool use was already present in the common ancestors of Homo and Paranthropus. What is, however, of particular interest is the evidence during geological time for brain-size increase in the Paranthropus lineage, independent of but parallel to that seen in Homo.258 Why it was that the brain sizes increased has, of course, been the subject of protracted debate, but the convergence in Paranthropus might help to constrain these possibilities. Thus, Sarah Elton and her colleagues reinforce one current idea when they write, 'The manufacture and use of stone tools as a means to access meat eating might have been a crucial factor in hominin encephalization. However, it is also possible that increased meat eating and exploitation of patchy resources occurred because the existing cognitive ability and skills of hominids enabled them to make tools, and therefore facilitated meat eating.'259

The likelihood that lithic technologies would evolve more than once has already been touched upon, and so it seems reasonable that at some time, sooner or later, one or more lineages would rampantly encephalize. Thus, in a discussion of early hominid evolutionary ho-mologies and homoplasies Daniel Lieberman and his colleagues260 remark, 'An additional question raised [by our study] ... is whether enlarged brains evolved more than once in hominid evolution ... there is in fact no theoretical reason why, if large brains are advantageous, that this should not have occurred independently among different Pliocene hominid lineages.' Acknowledging the many difficulties in obtaining enough reliable data, Lieberman and his colleagues comment that their analysis raises 'the interesting possibility that increased encephalization evolved independently in more than one clade of hominids.'261 In a similar vein, Gerrit van Vark262 has argued, on the basis of a multivariate statistical analysis of cranial material dating back to c. 1 Ma, that two separate lineages show independent trends towards human form. As he remarks, '"Hominisation" is not as unique a process as many may think.'263 Nor does van Vark think this process of hominization is yet complete: in this case it may well be legitimate to extrapolate existing trends into the future.

While these ideas will certainly be controversial, it is beyond dispute that much of the hominid evolutionary 'bush' became associated with stone tool cultures. A striking and much remarked-upon feature is the conservatism of these cultures,264 with vast epochs of time elapsing before there is a noticeable shift in technology. Stone tools, of course, may give a rather one-sided view of these cultures. Thus, the discovery of wooden spears 400 000 years old,265 evidently designed to act as javelins rather than to be employed in thrusting, are timely reminders, not only of the cognitive range of extinct hominid species (in this case Homo erectus or a near-relative), but also of how much of these cultures may have literally rotted away.

Other hints of increasing sophistication are the controlled use of fire from approximately 400000 years ago266 (earlier records are controversial267), and pathological conditions that imply protracted care of the sick. These include what appears to be a case in Homo erectus of hypervitaminosis, an agonizing condition brought on by the unwise consumption of carnivore livers containing vast and potentially lethal quantities of vitamin A, with the implication that the afflicted individual received long-term care rather than being left to the hyenas.268 Despite these hints, and remembering that much evidence has been lost, it still seems that in general the pace of cultural change was, from our technophilic perspective, torpid in the extreme. Much has been made, and justifiably so, of the so-called Upper Palaeolithic Revolution.269 This refers to the dramatic appearance of sophisticated tool-kits,270 ornaments, e.g. beads, and perhaps musical instruments271 beginning about 50000 years ago. On the last item, Patricia Gray and her colleagues comment, 'Remarkably, many different types of scales can be played on reconstructed prehistoric flutes, and the sounds are pure and haunting.'272 This culture is, of course, a product of our own species and unsurprisingly their anatomy is indistinguishable from ours. Yet the so-called anatomically modern humans appeared substantially earlier, about 125 000 years ago, although prior to the Upper Palaeolithic Revolution for the most part they churned out a markedly different set of stone tools. These are referred to as the Mousterian culture. While these implements are perfectly adequate they are decidedly less complex, and once again strangely conservative, showing little change over aeons of time.

What may have been a rather abrupt transition from Mousterian to the more advanced Aurignacian tool-kits in Europe was possibly heralded by substantially earlier developments, such as those reported from central Africa.273 Indeed, the very concept of an Upper Palaeolithic revolution is now in question.274 Nor should this surprise us: perhaps what happened in ice-age Europe was a telescoping of events that elsewhere was a more protracted process. Surely the important point is that over a relatively brief time we see a clear emergence of advanced cognitive abilities. Nor should we automatically assume that the emergence of sophisticated cultures can occur only once: evidence for multiple origins for agriculture and domestication of animals points in exactly the opposite direction. Nevertheless, the earliest occurrences of such cultures are highly sporadic,275 and there does seem to be a real shift in the mental landscape when, about 55 000 years ago, the first compelling evidence for symbolic composition is found.276 Here, too, there are earlier harbingers such as a fragment of bone 70000 years old from the Blombos cave in South Africa, with a set of largely parallel cut marks,277 and even more spectacularly, and from the same site, rare pieces of engraved ochre.278 Here arguably is the key benchmark, in what was to lead to a cultural effloresence made famous by the cave paintings, figurines, and other sculptures that were in production from about 35 000 years ago. If humans were inevitable from the Cambrian period, a visit to the Moon was on the cards when the Palaeolithic painters surveyed the bare cave walls of Les Chauvet.

So here, at long last, we have found an example of evolutionary uniqueness. Other species of hominid might warm their bodies beside the fire, hunt with spears, and care for their sick, but were they really capable of abstract thought and symbolic representations?

Who are those figures in shadows, tracking our own history? Step forth the Neanderthals, a much-researched and on occasion muchabused group.279 Either way their study is accompanied by continuous controversy. Nevertheless, the majority opinion is that they represent a separate species, Homo neanderthalensis, a view established on differences in skeletal structure280 and development281 and more recently on the basis of the recovery of ancient DNA.282 Their massive and powerful construction, and details such as huge noses, are evidently adaptations to living in hostile, near-tundra conditions, of dealing with bouts of intense cold, and an erratic food supply that led to the adoption of hunting patterns rather different from those of Homo sapiens.283 Our and Neanderthal brain sizes are equivalent, and it is beyond all reasonable doubt that they controlled fire and employed the red pigment ochre, possibly for body decoration. Unequivocal evidence for cannibalism also exists,284 but the discovery of skeletons with severe impairments indicates that the infirm and crippled were at least sometimes tended to. Famous examples come from the Shanidar caves in Iraq.285 Of the series of Neanderthal skeletons, a majority shows evidence of various traumatic injuries. One of the individuals (Shanidar I) had particularly dramatic injuries, perhaps caused by a rock fall, that included cranial damage, a fractured foot, and an arm that had withered. This individual lived, for a Neanderthal, to a relatively advanced age, and the extent of his disabilities indicates a society capable, for whatever reason, of care and compassion.286 Even so, Neanderthal life was evidently robust and demanding. A general survey of Neanderthal trauma287 confirms the prevalence of injuries, as well as the very high incidence of neck and head damage. Thomas Berger and Erik Trinkhaus remind us that although the old and infirm might receive care, the general 'dearth of older Neanderthals' suggests that 'these hominids did not sacrifice the survival of the social group as a whole when it was threatened by an immobile individual'. Despite the likely employment of spears in hunting, these may have been used principally for thrusting rather than throwing. As Berger and Trinkhaus dryly note, 'Given the tendency of ungulates to react strongly to being impaled, the frequency of head and neck, as well as upper limb, injuries seen in the Neanderthals should not be surprising.'288 And if the Neanderthal escaped the charging ungulate, then there was also the risk of attempted murder.289 What is especially intriguing is the evidence for deliberate burial (Fig. 9.6). This too

Neanderthal Burial

figure 9.6 The Kebara Neanderthal burial. Inhumation was probably deliberate and may have involved decapitation and removal of the lower jaw. (Reproduced from the figure on p. 229 of B. Arensburg et al. (1985), Une sepulture neadertalienne dans la Grotte de Kebara (Israel). Comptes Rendu des seances de l'Academie des Sciences, Paris, ser. 2, vol. 300, pp. 227-30) with permission of the Academie des Sciences, Paris.)

has attracted scepticism; one paper is entitled Grave shortcomings.290 Certainly the evidence for the laying of flowers with the corpse seems circumstantial,291 nor is there convincing evidence for grave goods, at least in the eyes of most investigators.292 Nevertheless, it seems almost certain that at least in certain circumstances the Neanderthals took care of their dead;293 perhaps for hygiene, perhaps for some other reason?

And yet the consensus is that a vital spark was missing. It seems inconceivable that Neanderthals with their use of fire and burial of the dead did not have some kind of language; who knows, perhaps they sang? However, the only tangible evidence, which depends specifically on the position of a small bone (the hyoid) in the throat, is only indicative of some sort of language ability.294 Differences between the vocal tracts of Neanderthals and modern humans do, however, exist, and while there is no doubt that the Neanderthals had a facility for language, there is still a fierce debate about whether their fluency approached that of modern humans.295 The general consensus, however, seems to be that to a first approximation Neanderthals and humans were equally fluent. Richard Kay296 and his colleagues, for example, use the size of the hypoglossal canal, which supplies the nerves to the tongue, and which is effectively the same size, to argue that vocal capabilities of Neanderthal and human were equivalent. A similar conclusion297 is based on the evidence for, and origins of, thoracic nervous innervation and its links to sound control. Language is also consistent with the production of sophisticated stone tools, but one has to note that these tools are functional and conservative. To be subjective, there is little sense of beauty in their form.298 In fact, the so-called Mousterian tool-kits, made both by Neanderthals and by humans, are in a European context similar in range of types and skills in execution, until about 50 000 years ago when we begin to diverge in technological complexity and usher in the next cultural stage, the Aurignacian.299

In contrast, the Neanderthals seem to have plodded on. Judged from about 40 000 years ago, but with foreknowledge of their coming doom, one might have predicted the last Neanderthal to have gone to the grave300 still clutching in his or her massive hand a Mousterian tool. This, however, did not happen, because about 35 000 years ago there was a rather extraordinary cultural effloresence. Exemplified by what is referred to as the Chatelperronian,301 it is marked by

figure 9.7 Chatelperronian culture, in the form of perforated or incised teeth and bones, presumably to be worn as ornaments. (Reproduced from fig. 13 of Zilhao and d'Errico (1999; citation is in note 308), with permission of the authors and Kluwer Academic/Plenum Publishers.)

the Neanderthals not only making more advanced tools but, even more remarkably, by shaping bones and teeth to form artefacts. Notable finds from the excavations at Arcy-sur-Cure302 include necklace pieces (Fig. 9.7) composed of canine teeth and fossils. This breakthrough, which for obscure reasons did not spread to Iberia,303 took place after tens of thousands of years of seeming cultural stagnation, and has been interpreted as largely imitative on the Aurignacian cultures of the incoming H. sapiens, if not acquired by trading or even scavenging abandoned sites.304 A useful analogy, suggested by Paul Mellars, is with the cargo cults of such islands as New Guinea and the New Hebrides.305 On some of the islands, such as Tanna in the New Hebrides where the John Frum cult still exists, the indigenes construct elaborate cult centres which include model aeroplanes, upon which it is hoped the desired objects will arrive.306 If these artefacts had been found in an archaeological context, it would not be sensible, as Mellars reminds us, to conclude that the islanders had any practical knowledge of aerodynamics. So too, perhaps, with the Neanderthals: 'Very good, Arthur; not bad at all, now if we can just hold the flint a bit higher ... well, never mind, I expect we can use it for something; now if you would like to bring a flint from that pile over there, we'll continue the lesson .. .'307

A radically different interpretation, however, is now being put forward that denies that the Chatelperronian culture is imitative. Instead the evidence is used to indicate that this breakthrough, where a necklace had meaning, was independent from H. sapiens and thereby convergent.308 To say that this proposal is controversial is putting it mildly: battle-lines are being drawn.309 The disagreements revolve around the dating, which depends on radiocarbon technology, and the stratigraphic order of the various cave deposits. The cave stratigraphy is notorious for the complexity of the infill histories and for the problems of subsequent disturbance, by hominids, animals, or even careless excavators. Yet the evidence is intriguing. In one key locality, the famous Grotte du Renne at Arcy-sur-Cure in Yonne, central France, exceptional Chatelperronian skeletal remains and artefacts have been excavated. Interestingly, despite the finesse of the artefacts, the skeletal morphology of these Neanderthals remained highly robust, although there are some hints of minor changes in the loading patterns of the forearm and shoulder.310 In any event this Neanderthal occupation patently underlies and is separate from the subsequent Auriginacian influx that marks the arrival of H. sapiens. These Chatelperronian tools were not imported from some trading post, but were obviously manufactured on site.

In addition, the Chatelperronian itself was not completely homogenous. Some argue that it is divisible into a series of separate and advanced cultures (with names like Szeletian (a central and east European culture) and Uluzzian (in Italy), all doing approximately the same thing at the same time. Interestingly, Neanderthal culture has its own characteristics,311 and among the material recovered is a bear penis-bone (baculum) with carved circular markings.312 This find, from Croatia, is probably from an upper level of Neanderthal occupation, but it is possibly derived from a deeper horizon, dated at c. 42000 years bp. This is not to say, incidentally, that cultural contacts did not exist between some Neanderthals and modern humans, although the evidence for this is conjectural (see note 312). Certainly the idea that the two species (if they were genuinely separate)

may have interbred is intensely controversial.313 But if they did at least have cultural contacts, it is also worth remembering that even if the Chatelperronian cultures arose independently (which seems likely) then if there was any contact it would almost certainly be a two-way process, and Homo sapiens would also have picked up useful tips.314 Concerning this ongoing controversy Steven Churchill and Fred Smith (note 299) take a measured view, and although noting that 'the last Neanderthals seem to have held to a Mousterian way of life to the bitter end [see note 303] ... [others] appear to have been full participants in the evolving Upper Paleolithic ... [and] suggest that Neanderthals had cultural capacities on a par with those of early modern humans.'315

Translating the stratigraphy of the caves and their contained artefacts into the daily life of a band of humans or Neanderthals, each with the daily pressures of avoiding hunger and charging ungulates, surviving illness, and on occasion encountering other groups, is bound to be contentious. Tools were made, but are now silent. When does innovation and novelty stop being imitation? This problem is not confined to the origin of the Chatelperronian cultures. For example, it has been suggested that similarities in the tools made in the Upper Palaeolithic of Europe, and specifically the Solutrean culture (c. 20000 years ago, effectively the people who painted Lascaux), and the somewhat younger North American Clovis culture can be explained only by transAtlantic crossings thousands of years in advance of either the Vikings or the Spanish. The majority of researchers are, however, unconvinced, and interpret such resemblances as there are between Solutrean and Clovis are simply convergent.316

Still, it is sensible to keep an open mind. What, for example, are we to make of a terracotta head, apparently about 2000 years old, that if displayed in a museum would be put in the Roman section? The only problem is that the head is from Mexico, and was found in a sequence that is unequivocally pre-Columbian.317 A Roman ship blown off-course from Spain, crossing the Atlantic?318 Let us further imagine that two of the passengers were a friend of Paul the Apostle and a relative of Pliny the Younger. The ship moves slowly across the Caribbean: one of them looking at the New World with radiant hope, while the pagan sinks into gloomy resignation.319

To conclude: it is emphatically not my purpose to argue that agricultural ants, New Zealand kiwis, playful dolphins, or tool-wielding capuchin monkeys should have inherited the world as the most sentient species. Rather it is the simple observation that the ubiquity of convergence will lead inevitably to the emergence of recurrent biological properties that define the fabric of the biosphere. Rerun the tape of life as often as you like, and the end result will be much the same. On Earth it happens to be humans, just as the author of this book happens to be an academic in Cambridge. So what? Self-evidently we humans are now utterly different. We have new concerns, new priorities and questions, and, most important of all, new possibilities.

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