Masters of the Planet (27 page)

The morphologies of both the skulls and the postcranial bones of the Sima hominids are like nothing known from anywhere else, although they do show a clear affinity to
Homo neanderthalensis.
Still, they were equally clearly not Neanderthals. In its morphology
Homo neanderthalensis
is a well-delineated species, with a large number of highly characteristic features in its skull. But not all of the distinctive Neanderthal traits are seen in the Sima hominids, though some are—for example, the thick ridges that arc delicately above each eye and a curious oval depression at the rear known as the “suprainiac fossa.” The Sima folk remained less specialized, more ancestral, in such features as their steep-sided cranial vaults and relatively broad lower faces. They were certainly forerunners of the Neanderthals; but, befitting their early time frame, they were not the same thing.

It is not easy to date a pile of bones at the bottom of a pit, but fortunately lime-rich water flowing over the rubble pile at the Sima had laid down a limy cap over it soon after it had accumulated. And modern techniques make it possible to date such “flowstones,” using radioactive isotopes of uranium deposited in the calcite crystals that form the stone. These unstable isotopes decay at a constant rate into stable isotopes of thorium that were not originally present, so the ratio between the two allows you to determine the time elapsed. High-precision measurements of both isotopes in the Sima flowstone have produced a series of dates clustering around 600 thousand years ago, with a minimum of 530 thousand. The possibility remains that the hominid bones are younger than this, as was at first believed; but either way, in terms of time they are well placed to be those of Neanderthal precursors.

So what was this jumble of fractured and disarticulated ancient individuals doing at the bottom of a deep, narrow shaft in a gloomy cave interior? This was certainly not a living place, and it is highly unlikely that 28 individual hominids fell in there by accident. Neither is there any suggestion that this could have been a carnivore den, although various carnivores did tumble in, including cave bears that may have become trapped while looking for a place to hibernate. Other carnivores may then have been attracted by the stench of their decaying bodies. But there is not one fossil of a browsing or a grazing mammal down there: this is anything but a random sampling of the local fauna. The Atapuerca researchers suggest that the hominids must have been deliberately thrown into the pit by their fellows, presumably as a way of disposing of them after they had died, somewhere outside the
cave
.

Skull 5 from the Sima de los Huesos at Atapuerca in Spain. Broken but restored, this is the best-preserved skull from a site that has yielded the fragmentary remains of at least 28 individuals some 600 thousand years old— the most amazing trove of hominid remains ever found. The population from which they came was a precursor to the Neanderthals. Photo by Ken Mowbray.

Not everyone is impressed by this explanation, but in its support the Atapuerca group point to one striking piece of evidence: the one and only artifact found in the pit happens to be a splendid handaxe made from rosy quartzite. Not only is this kind of artifact an unusual occurrence at any Atapuerca site of this age, but quartzite itself is also rare there. Early stone tool makers prized good raw materials, and, especially given the aesthetic appeal of the stone from which it was made, the Atapuerca group is almost certainly right in believing that “Excalibur” was a very special object to its possessor. Whether they are also right in believing that it was an overtly ceremonial object—it was apparently never used for any practical purpose—is more debatable. Even more hypothetical is the added deduction that this was a symbolic piece, tossed
into
the pit as part of a funerary rite. But if indeed it was such a thing, it would at the very least imply that the Sima hominids had developed a substantial sense of empathy, and it would certainly bolster the Spanish researchers' view that the Sima folk already possessed some power of symbolic thought.

Still, this is reading a great deal into one isolated observation, the true significance of which is entirely conjectural. Sadly, we have no other archaeological knowledge of the Sima people. No fossils like them have yet been found anywhere else, and we cannot confidently associate them with material expressions from (very rare) archaeological sites of their period in Europe (although it's not altogether impossible that the Schoeningen spears or the Terra Amata huts might have been the work of later members of their Neanderthal lineage, rather than of the contemporaneous
Homo heidelbergensis
).

The situation has been confused yet farther by the finders' allocation of the Sima fossils to
Homo heidelbergensis
(which they clearly are not), instead of to a new species affiliated with the Neanderthals (which
Homo heidelbergensis
is clearly not). But maybe there is an alternative approach to determining whether or not the Sima folk were symbolic, since their morphology leaves no doubt that they belong to a form antecedent to
Homo neanderthalensis.
The later Neanderthals left behind a rich archaeological record, one that furnishes us with a much firmer base on which to make such judgments. If the Neanderthals were symbolic, then the Sima hominids might have been. But if their successors the Neanderthals were not symbolic, then they weren't either.

TEN

WHO WERE THE NEANDERTHALS?

H
omo neanderthalensis
occupies a very special place in the hominid pantheon because it was the first extinct hominid species to be discovered and named, back in the mid-nineteenth century. Largely as a result of this accident of history, the Neanderthals have always loomed very large in considerations of our own evolution— although it has for long been evident that they were not direct human precursors as was suggested early on, and there is fairly general agreement by now that they deserve recognition as a distinctive hominid species in their own right. This distinctiveness is evident in the fact that there is surprisingly little disagreement in the normally contentious paleoanthropological fraternity over which particular fossils are Neanderthal.

A braincase from a site in the north of France known as Biache-St-Vaast represents the earliest distinctively Neanderthal fossil. It dates from at least 170 thousand years ago (MIS 6), and the accompanying fauna indicates that conditions then were moderately cold. If you want to push the oldest Neanderthal occurrence back a bit farther, you might include a somewhat less complete braincase from the German site of Reilingen that is uncertainly dated to MIS 8, perhaps 250 thousand years ago. This is about the presumed age of another, more complete specimen from
Steinheim,
also in Germany, that possesses more Neanderthal features than the Sima hominids but that, like them, is not fully Neanderthal. These tantalizing observations hint that events in the hominid history of Europe around this time were more complex than has generally been assumed, and it also suggests that we are never likely to find full-fledged Neanderthal fossils at more than about a quarter of a million years ago. Nonetheless, it's obvious that the Neanderthal lineage must have been present in Europe between Sima and Reilingen times, and it's possible that we know so little about it due to the effects of repeated glaciation and deglaciation in the region.

One of the reasons why we have such a good hominid record in Europe is the extensive occurrence of limestone rocks offering caves and overhangs that hominids would have been eager to exploit for shelter. The occupation debris they left behind in such places would regularly have been washed out by the water that flooded across the landscape each time the ice sheets melted; but the record is good enough to tell us that
Homo heidelbergensis
also existed in Europe during the tenure of the Neanderthal lineage. This knowledge strongly supports the idea that a complex minuet among hominid species was unfolding in Europe during the Middle Pleistocene (the period between about 780 thousand and 126 thousand years ago). If so, the large-brained Neanderthals were the victors in this particular contest, since by Biache times, if not well before, they were in sole occupation of the subcontinent.

In their 200-thousand-year tenure, the Neanderthals spread widely in Europe, and far into western Asia. Their fossils have been found as far south as Gibraltar and Israel, and what is reasonably an early Neanderthal archaeological site, dating from a warm interlude, has been found as far north as Finland. A recent report even places these hominids (by tools they are assumed to have made, rather than by their fossils) at a site in northern Russia not far from the Arctic Circle, at some 31 to 34 thousand years ago when conditions were considerably colder. In the west, Neanderthal fossils are known from north Wales in the British Isles, and numerous others are scattered eastward as far as Uzbekistan. A nondescript bone bearing the characteristic Neanderthal genetic signature has even been discovered farther east yet, at a site in the Altai Mountains of southern Siberia.

Neanderthal
sites are thus spread over a vast area of the Earth's surface, and occur at a huge variety of altitudes, topographies, and latitudes. It is, then, clear from its distribution alone that
Homo neanderthalensis
was a rugged and adaptive species, able to cope with a wide array of different environments. Still, Neanderthals notably tended to avoid areas that were uncomfortably close to the glacial fronts, and the total area within the enormous range that they were able to occupy at particular points in time must have varied widely amid the climatic vagaries of the Pleistocene. For example, during a cold snap during about 70 to 60 thousand years ago the Neanderthals seem to have been limited to Europe's Mediterranean fringes, while during the warmest parts of the following MIS 3 their traces are found far up into northern and central Europe.

This is particularly interesting since it has long been assumed, on the basis of their northerly Ice Age origins, that the Neanderthals were somehow “cold-adapted.” In sharp contrast to the African-derived and “tropically adapted”
Homo sapiens,
they were seen as creatures of the ice and snow. In reality there is very little to suggest this, either in the peculiar form of the Neanderthal nasal region, often interpreted as a mechanism for warming and humidifying cold and dry incoming air before it hit the fragile lungs, or in their limb proportions. These were long taken as adapted for the Arctic, but they actually seem to resemble what is seen in intensive modern foragers of varying backgrounds. The reality is that, over their long tenure, the Neanderthals ranged throughout many diverse territories and climates, to which they must have accommodated culturally. Indeed, it would have been impossible for them to accommodate otherwise, since it's been calculated that, under the coldest conditions these hominids endured, a 180-pound Neanderthal would have required an extra 110 pounds of subcutaneous fat to compensate for a lack of clothing. Being built like a Sumo wrestler is hardly what you might view as the ideal adaptation to a hunting lifestyle; and it is far more likely that the Neanderthals were as lean as Arctic peoples tend to be today, and depended on clothing and other cultural accoutrements for insulation and warmth.

Interestingly, analysis of two Neanderthal DNA samples (more on Neanderthal DNA in a moment) suggested that they possessed an inactive version of a gene affecting skin and hair color. Apparently, befitting their temperate origin, these individuals would have possessed pale skins and red hair. But, significantly, the gene variant in question is not one that is found among modern humans, even redheads. This one observation is by itself emblematic of the fact that we need to get away from seeing Neanderthals as a less successful version of ourselves, a hyper-adapted variety of modern human that put all of its eggs into the wrong
basket
.

A reconstructed Neanderthal skeleton (left) compared with that of a modern human of similar stature. The comparison reveals two distinctly contrasting hominids. Apart from the cranial differences, note especially the very different shapes of the thoracic and pelvic regions. Photo by Ken Mowbray.