One of the great paradoxes in palaeoanthropology is how modern humans in Europe survived the last glacial maximum whereas Neanderthals did not. In fact they became extinct some 10 thousand years before conditions reached their coldest. The paradox lies in the fact that Neanderthals were superbly adapted physiologically and behaviourally to life in cold, harsh conditions, having lived through the previous glacial period since at least 200 ka ago. Modern humans evolved, since first appearing around 160 ka, by adapting to conditions in Africa – an environment far different from that of Europe in every conceivable way – and bands migrated outwards, probably because of growing aridity as global climate cooled. Their future was akin to that of Africans from modern Kenya, should they decide to migrate to Arctic Canada. Quite probably Kenyans would survive, because the Innuit are supremely generous and friendly people. They have to be in order to have survived their chosen environment. It is this paradox that concerns archaeologist Paul Mellars of Cambridge University (Mellars, P. 2004. Neanderthals and the modern human colonization of Europe. Nature, v. 432, p. 461-465). Genetic evidence from recovered Neanderthal DNA shows conclusively that the two occupying groups in Europe did not interbreed to any significant extent, so the paradox can therefore not be resolved by complete hybridisation. To what extent were modern humans better equipped with tools than were Neanderthals? The archaeological record shows that from about 40 to 35 ka there was a burst of cultural advance among moderns, that spanned the Middle East to the Atlantic shores of Spain – the Aurignacian technology. It coincided with an equally explosive spread of aesthetic culture, involving such symbolism as to be widely considered as a mark of sophisticated language and communication, perhaps a sign of an advance in brain structure that Neanderthals did not experience. One of the big surprises in recent archaeology of this crucial period was that modern human remains associated with early Aurignacian artefacts turned out to be burials later than the tools were discarded. To some, this left open the possibility that the technological advance may have been achieved by earlier occupants – the Neanderthals themselves. Indeed there are signs that these original Europeans did make cultural advances around that time, in the form of the Chatelperronian artefacts. Mellars points out that moderns of the time did not bury their dead near habitations, whereas Neanderthals made a habit of it, so the inference of especially smart Neanderthals is probably unfounded. There are two geographic patterns associated with the Aurignacian, one arcing through Central Europe to France, the other along the Mediterranean coast, each showing distinct differences in technology. This is regarded as support for two populations of colonising moderns. The Chatelperronian is now regarded as one of many signs of some kind of cultural transfer between Neanderthals and moderns, and therefore of regular contact. Whatever those contacts involved is unknown, but immaterial as regards the fate of the Neanderthals. They disappeared without a trace, by 30 ka at the latest. Mellars’ review concludes with the view that this extinction was a matter of outcompetition, as conditions were steadily deteriorating towards the last glacial maximum. It could well be that moderns, faced by the perils of a move to harsher conditions that were oscillating rapidly due to Dansgaard-Oeschger events, were forced to adapt or perish. The Neanderthals did not, or they did it too late. Their culture had served them well, and why should they have changed it?
A discovery that will run and run?
Do you know why humans have prominent buttocks (the ape has none worth a sidelong glance)? I thought not; most people do not wish to know. Here is how to find out. Begin to walk, preferably in secluded woodland. Now clutch each “cheek”, one in either hand. Do you notice anything? No, the gluteus muscles do nothing, apart from wobble a bit. Now, if this is possible, begin to lope along the path, still with a buttock in each hand. There, they work! Hominids are not just striding bipedalists, but evolved to run: not so fast as to collapse after a hundred metres, but kilometre after kilometre at a relentless lope. This is the conclusion from anatomical and bio-mechanical study of hominid remains, going back to our oldest undisputed ancestors (Bramble, D.M. & Lieberman, D.E. 2004. Endurance running and the evolution of Homo. Nature, v. 432, p. 345-352). The outcome is that modern humans, and probably every earlier species of Homo, can and did run any other animal to exhaustion. The australopithecines probably could run down a hedgehog, but not prime meat. The study goes further, since there is more to running than leaning forward and putting a leg out to stop us falling on our faces. The arms are involved, and flexure of the waist. Mechanically, a higher waist and shorter arms are more effective aids to running, as of course are proportionately long legs. The technical arguments in this hypothesis are somewhat unfamiliar, except to the sports scientist, but one immediate conclusion is easy. No modern hunter-gatherer really likes to run a marathon each day, even though they could, and would much rather sit and watch the world go by, so long as he or she is fed. Unless the utter pointlessness of prolonged physical activity, other than a means of sustenance, becomes a cultural necessity for other reasons, the next stage in human evolution may well see the buttocks atrophy. Legs will shorten, the waist drop and the arms lengthen, once more, to help us knuckle-walk up to the chip shop. There may only be one way to preserve the buttocks; to encourage wolf packs in city parks.
Something to chew over
Much of the human evolutionary story depends on the most enduring of fossil material – teeth. So, dentists have been drawn increasingly in palaeoanthropology. Since species are defined as whole organisms, the use of such tiny fragments as teeth should be worrying. But they are often the only material, and specialists in dentition have convinced themselves that teeth “work” as phylogenetic indicators. But there are always dental variations between individuals, and therefore a danger of doing something akin to cheating with a jigsaw puzzle; forcing misfits into the cussed blue sky part in order to get on. Recent research on the genetics that underlie the development of mouse teeth (Kangas, A.T. et al. 2004. Nonindependence of mammalian dental characters. Nature, v. 432, p. 211-214) shows that different levels of a protein (ectodysplasin) affect the shape changes during development of dentition.. Ordinary mice have different molars, depending on tiny differences in the growth points of tooth crowns during dental development, and that depends on ectodysplasin levels. Clearly, major differences among fossil teeth ought to point to adaptation (and speciation) to very different diets and ways of biting. But now there is a devil in the detail of the teeth of mammals, although the authors do not extend their observations explicitly to those of hominins. Specialists in human speciation will probably rationalise away the possibility of something going awry with the hominin clade, and perhaps rightly so, if the implications of Kangas and colleagues work diffuse to their arena. However, everyone is aware of the dramatic polymorphism of human mastication, from mouth-filling “tombstones” to a tiny pointiness that worries the experienced observer.