Masters of the Planet

by Ian Tattersall

  This latter species, some 780 thousand years old, is of particular interest because the Atapuerca scientists believe it may represent the common ancestor of the lineages that led to Homo neanderthalensis on the one hand, and to Homo sapiens on the other. But while the Gran Dolina does lie more or less in the right time zone for its hominids to play that role, just where they stand in the evolutionary picture remains equivocal. Indeed, it seems at least equally likely that the Homo antecessor fossils are evidence of an early “failed” hominid foray out of Africa and into Europe that did not have a direct ancestral connection to the Neanderthals who later established themselves in the European Peninsula. Still, if there is a direct connection back to the Sima del Elefante hominid, the first hominid occupation of Europe was a long one; and if you are looking for continuity, you might find further evidence for it in the fact that the crude stone tools from the two Atapuerca sites do not differ much.

  The spot at the Gran Dolina where the hominids were found seems to represent an ancient cave entrance that was occupied by hominids during a relatively mild and humid period. And the Atapuerca scientists’ claim that Homo antecessor represents the common ancestor of Neanderthals and modern humans is no less remarkable than their conclusion that the bone fragments assigned to this species show evidence of cannibalism. Fossil bones so far recovered from the Gran Dolina are typically badly broken, and many of them bear marks left by slicing, chopping, and scraping with stone tools, along with fractures of a kind strongly suggesting butchery. What’s more, allowing for differences in anatomy among species, all of the bones, human and nonhuman alike, were treated in an identical fashion. And this implies that all of the cadavers they represent were used for the same purpose, namely consumption. There is certainly no evidence of any special or ritual treatment of the human remains. As a result, there is a strong case to be made that hominids were eating other hominids at the Gran Dolina 780 thousand years ago; and though not everyone is entirely happy with this interpretation, the argument for cannibalism is a strong one and the Atapuerca team has recently issued a robust defense of its conclusion.

  Demonstrating cannibalism is just the beginning, as it raises a host of questions, foremost among them, who was eating whom, and why? To modern humans, cannibalism has all kinds of symbolic overtones, depending, for instance, on whether you are eating your kin or strangers. The Atapuerca group dismisses any symbolic implications at the Gran Dolina, emphasizing that the 11 children and adolescents represented in the butchered sample received no special handling, and that the butchery techniques involved were designed to extract the maximum amount of edible material, including the brains. Because they can find no evidence to support the idea that the butchered humans at the Gran Dolina were the victims of a single episode of group starvation— indeed, the butchery may have taken place over several tens of thousands of years, in the midst of a rich habitat—they propose that cannibalism was a regular part of the subsistence strategy of Homo antecessor. They even go so far as to speculate that the tender ages of those eaten might imply that they were the vulnerable victims of hunters sent out to raid neighboring groups.

  Sadly, there is not much direct evidence from the Gran Dolina itself, apart from the butchered fossil carcasses and the stone implements, most of them knapped right there in the cave, that were used to dismember them. There is no indication of the use of fire, for example, or of any other activities that might have been associated with the hominid occupation—although some plant vestiges might indicate a more rounded diet than the bones alone suggest. Almost certainly, the Atapuerca researchers are right to reject any implications of ritual in the butchered hominid assemblage; and if they are correct in concluding that cannibalism of this very matter-of-fact sort was a routine component of dietary life at the time, the clear implication is that the hominids concerned did not have the kind of regard for others that is typical in modern human societies today. Wherever it has been documented in the historical record, socially sanctioned cannibalism, whether within or among groups, has always been a “special” activity, surrounded by its own rites and ambivalences. The chillingly prosaic nature of the cannibalism at the Gran Dolina implies something totally different—and to us, totally alien.

  NEANDERTHAL ORIGINS

  Although it is not possible to draw a straight line connecting Homo antecessor at the Gran Dolina with the later Homo neanderthalensis, yet another site in the astonishingly fecund Atapuerca region furnishes us with the best evidence we have for an early member of the Neanderthal lineage. The species Homo neanderthalensis itself does not show up in the European fossil record until less than 200 thousand years ago; but a stone’s throw away from the Gran Dolina, the large Cueva Mayor cave has produced one of the most extraordinary phenomena in paleoanthropology, and one that gives us a marvelous insight into the early stages of the Neanderthal lineage. Well within the cave is a vertical shaft, almost fifty feet deep, at the bottom of which a small, cramped chamber has delivered the greatest concentration of hominid fossils ever discovered, anywhere. Hominid fossils are an extraordinary rarity, and paleontologists usually count themselves lucky to find just one or two. But the lead excavator of this Spanish cornucopia once remarked to me that his team was the only one in the world with the luxury of deciding how many hominid fossils it wanted to excavate in the next field season—a few dozen, a hundred—and then quit when the quota was filled. No wonder this amazing place is called the “Sima de los Huesos”—the Pit of the Bones. It’s a hellishly cramped, difficult, and uncomfortable place to excavate, to be sure; but well worth every painful moment.

  The Sima was initially discovered by spelunkers, who alerted paleontologists when they discovered the bones of extinct cave bears. And since systematic excavations started there in the early 1990s, the site has produced hundreds of hominid fossils, representing the remains of at least 28 individuals of both sexes. Although the individual bones are typically badly broken, the preservation of the bone itself is remarkable, and scientists have been able to reassemble the many hundreds of pieces into half a dozen more or less complete crania and numerous elements of the postcranial skeleton. A homogeneous sample this large of a single extinct hominid species from one place is unprecedented; and the Sima gives us a unique glimpse into the biology and even the demography of an extinct hominid species. The individuals whose bones were found at the bottom of the pit range from a single child to a handful of older adults in the 35- to 40-year range, and half of them had died between the ages of 10 and 18. Presumed males were larger than presumed females to about the same degree you find in modern humans, and one male stood almost six feet tall.

  These were heavily built folk, with robust bones, and each probably weighed a good bit more than a modern human of the same height. Almost certainly, they were immensely strong compared to us. At the same time, their brains were on average a little smaller than ours, three crania ranging in volume from 1,125 cc to 1,390 cc. Their pelvises were broad, with birth canals capable of accepting the head of a modern newborn. Once individuals had emerged into the world, they faced a life reasonably free of dietary stress. Episodes of malnutrition are reflected in the enamel of developing tooth crowns, and evidence of such events is rarer at the Sima than it typically is in recent Homo sapiens populations. This is something not unexpected in an environment that is believed to have been rich and productive.

  Studies of the mammal bones found at sites more or less contemporaneous with the Sima imply that northern Spain had cooled off a bit since Gran Dolina times, but that the Sima folk had lived in an open woodland landscape supporting a diverse fauna. The Atapuerca researchers believe that the Sima hominids would have been major predators in this setting, though they would also have been in competition with at least two species of lionlike large cats, recent arrivals in the region. The prevalence of arthritis in the Sima individuals’ jaw joints coincides well with heavy wear on their teeth that indicates not only that they ate a fairly tough and abrasive diet, probably with a
gritty plant component, but that they used their teeth extensively for such tasks as processing hides. And although the best-preserved skull shows evidence of a dental infection that may have (very painfully) killed its owner, many teeth in the sample show a concern for dental hygiene in the kind of grooving that comes with the frequent use of toothpicks.

  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?

  Homo 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 t
he 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.