Masters of the Planet (12 page)

Meanwhile, those butchered carcasses also suggest much about both the early tool-wielding hominids themselves and the cognitive level they had achieved. Rock suitable for making tools does not occur everywhere on the Rift Valley landscape over which the early hominids roamed. And when they needed to butcher a large animal carcass, the evidence is clear that they assured the availability of good tool-making materials by carrying appropriate rocks around with them. Especially after we pass the two-million-year point, it becomes reasonably common to find the fossilized remains of cut-marked butchered carcasses with ancient stone tools scattered around and even within them. Characteristically, the tools themselves were not made from stone naturally available in the immediate area; sometimes the nearest natural source was often several miles away. In such cases the fine-grained rocks
needed
for tool-making must have been carried in from at least that far afield. What's more, they were not brought in as slimmed-down finished tools. We know this because the tool-making process didn't just produce one sharp tool after another. A single cobble might have produced two or even several cutting flakes, but in the process a lot of “debitage”—unusable fragments of stone—also resulted. And archaeologists have repeatedly pieced together entire cobbles from both useful and useless fragments found at a single butchery site. Not only has this laborious process of reconstruction told them a lot about how the stone tools were made, but it also provides clear evidence that the heavy cobble had originally been carried in complete—evidently in anticipation of being needed for tool production. And it hardly seems likely that hominids would have lugged weighty chunks of rocks around for miles, if they were rarely going to use them.

This kind of anticipation and foresight is different from anything we see in chimpanzees. Certainly, they hunt. But they usually do it on a situational basis, according to opportunities that present themselves. And if they need an implement to perform an activity with, they fashion it from available materials on the spot. The early stone tool makers, on the other hand, seemingly set out knowing precisely what they were going to do—whether hunting, or power scavenging, or whatever—and what they would need to do it with. They also understood the properties of materials, and how to work them, in a way that chimpanzees don't. This is already enough to tell us that the early hominids had taken a cognitive leap of some kind compared not only to their Pliocene relatives, but to modern apes as well. Clearly, in their time the tool-wielding australopiths, and plausibly also their immediate non-technological ancestors, were by a substantial margin the smartest creatures around.

Sadly, at present there is much less to say about these ancient precursors than we'd like, although it's a good bet that they were very cooperative creatures. But if you crammed four hundred chimpanzees into the back of an airplane and flew them from New York to Tokyo, there's little doubt that on arrival you'd find that the chimps had all massacred each other. Chimpanzees are highly social beings by any standard, but they do not have the special kind of sociality that it takes to live in a world as packed with people as ours is today. We certainly didn't acquire this
particular
form of sociality in response to modern crowded conditions, for our population explosion is recent; indeed, hominids have typically been very thin on the ground, at least over the past two million years or so. Perhaps, then, we should seek earlier in our evolutionary history for the biological underpinnings of our peculiar social propensities. And one suggestion is that we should look to the biological role and environmental preferences of the early bipeds.

EARLY SOCIETIES

So far we have discussed much about chimpanzees and hunting, and this is certainly a reasonable thing to do if we want to place our ancient ancestors in the context of our (and their) closest living relatives—creatures that we can actually watch going about their business in the natural world. It is also true that an emphasis on hunting is deeply embedded in paleoanthropological tradition. Indeed, in the 1950s Raymond Dart, who described the very first australopith fossil (actually, the infant victim of a predatory eagle) back in 1925, was dramatically proclaiming that “the blood-bespattered, slaughter-gutted archives of human history” were a direct reflection of “this common bloodlust differentiator, this predaceous habit” of mankind's earliest ancestors.

However, while we are undoubtedly the world's top predator today, my colleagues Donna Hart and Bob Sussman have recently emphasized just how misplaced this focus on hunting in our early evolution is. They point out that we are not simply super-chimpanzees; and that for all their evolutionary nearness to us, chimps retain all the instincts of forest animals, even where they spend a lot of their time in thinly wooded settings, as at Fongoli. According to Hart and Sussman, what most fundamentally differentiated our very ancient ancestors from chimpanzees is that, unlike the living apes, they adjusted their entire way of life to the exploitation of forest-edge and woodland settings. We see this in their bipedality, in their teeth, in their geochemistry, and in a host of other features. The ecological move to these more open environments brought with it new opportunities for hominids, as well as extraordinary future possibilities; but it also came at a huge immediate cost. This penalty was, of course, vulnerability to woodland predators. It is impossible to overstate the significance of this new factor: no new force could have had anything close
to
the impact on small-bodied bipeds, venturing away from their ancestral habitat, that the ubiquity of predators must have had.

Given this inescapable reality, Hart and Sussman suggest that we should probably not look first to our very closest extant relatives for clues as to how our earliest relatives lived. Instead, we would be better off seeking indications from environmentally similar primates such as macaques and baboons. Even if more distantly related to the australopiths than chimpanzees are, these primates have made a similar ecological commitment to living with both the advantages and disadvantages of the expanding new habitat mosaic. True, it's probably about 25 million years since we shared an ancestor with them, but our basic primate biology is similar, as is our ecological bias. Moreover, the fossil record shows that our forebears in the period before about 2.5 million years ago were not much bigger than largish baboons. One big difference, though, was in the size of the canine teeth. Male baboons, in particular, have fearsome, slashing upper canine teeth with razor-sharp back edges, a defensive feature that was conspicuously lacking in our own precursors. And the quadrupedal baboons are far fleeter of foot (indeed, their ground-favoring relatives the patas monkeys can hit almost 40 mph when they have to). The australopiths were thus significantly more vulnerable in open habitats than the terrestrial monkeys are, and the predatory pressures on them would have been concomitantly greater.

As you'd expect from animals that are at least partially committed to the savanna, baboons and macaques are omnivorous, exploiting the resources of the grasslands as well as of the forest, although they are also modestly tied to sources of water. But although they move well out into the grasslands to forage during the day, they commonly cluster for protection at night in trees or on cliff faces. And like other conspicuous species vulnerable to predation, they live in very large groups consisting of multiple males and females of all ages. After all, the more eyes and ears there are, the more likely it is that someone will spot a faraway predator and raise the alarm. No surprise, then, that these monkeys are also quite vocal. Often the groups forage and move around in such a way as to keep the reproducing females and young in the physical center, while the more expendable young males remain at the vulnerable periphery, where they can also function as sentinels. Since the groups are large, they
are
well structured and organized, with complex individual relationships among the members. This orderliness is unlike what we see in chimpanzees, which live in groups that lack rigid spatial structuring—even though within them inter-individual relationships are yet more complex.

There is plenty of evidence, mostly in the form of fractured bones and carnivore tooth-marks, that early hominids were frequently preyed upon; and the indirect evidence of habitat and body size and anatomy speaks to the same thing. Hart and Sussman thus reasonably conclude that the very early hominids would have had the social characteristics not of hunters, but of
prey
species. Our ancestors were the hunt
ed,
not the hunt
ers;
and these authors believe that much in our modern behavior still reflects this. We'll return later to the subject of our behavioral heritage; but meanwhile, Hart and Sussman identify seven strategies used by terrestrial monkeys that they believe early hominids would almost certainly have employed in their vulnerable new niche:

1. Live in large groups, from 25 to 75 individuals. There
is
safety in numbers. Perhaps influenced unconsciously by the knowledge that the human nuclear family is usually small in our own society, and more consciously by the demographics of predators, paleoanthropologists have tended to assume that early human groups were limited in size. As we've seen, bipedality has been linked with pair-bonding, and the large size differences between males and females of
Australopithecus afarensis
have invited comparison with gorillas, which usually live in groups of under 20 individuals that are dominated by a “silverback” male. For vulnerable prey species, though, significantly larger social groups would plausibly have been the norm.

2. Be versatile. Don't put all your eggs in one basket, as it were, but use all the environments and substrates available to you. We know that this rule applied to the early hominids, which combined bipedality on the ground with significant agility in the trees. Monkeys mostly achieve this versatility by staying small and generalized; early hominids did the same thing by combining seemingly contradictory specializations. It seems pretty clear that the hominid “have your cake and eat it too” locomotor strategy was not a transitional adaptation by creatures who were caught in the act of descending from the trees to the ground. They thrived on this way of life for many millions of years; and even
conditions
that we perceive in retrospect as “intermediate” must have been entirely functional in their day. Their body form indicates that early hominids were expressing a stable strategy, the diverse components of which, including the terrestrial leg and pelvis and the arboreal shoulder girdle and arms, seem to have been well accommodated to environmental necessity—despite the vulnerabilities inherent in the new way of getting around on the ground.

3. Be flexible in your social organization. Avoiding predators is fine, but it shouldn't come at the cost of starving yourself. On the savanna especially, the kinds of resources that a primate may readily access tend to be scattered, and are rarely abundant in one place. The large social unit should thus break up into smaller ones to allow more effective foraging for scarce resources, but all must be ready to re-coalesce into the larger group when real danger threatens.

4 and 5. Although males as a category are more reproductively dispensable than females are, have more than a single male in the social group at all times, even when smaller subgroups are roaming around. And use those males as sentinels, especially where males are larger than females and better able to discourage predation. Upright locomotion actually may help here, because it makes individuals appear larger to predators, and may fail to trigger an attack response in the way that horizontal silhouettes do.

6. Select your sleeping sites carefully. Assemble the group at night in trees or other places of comparative safety, and during the days stay as much as possible in areas of comparatively dense vegetation. When moving through open areas, maintain the largest possible group size.

7. Be smart. The better you are able to read and interpret the environment, the safer you will be. The better you communicate, the more effectively all members of the group will be able to avoid predators. Significant increases in hominid brain size—and, presumably, in intelligence—may not have really progressed until our precursors had been outside the dense forests for millions of years, and our own genus
Homo
had emerged. But the change of environment initiated by the first bipeds may well have been a critical enabling factor, setting the scene for later developments.

These
seven strategies certainly do not add up to a full portrait of our ancient ancestors as socioeconomic beings. At present we can be confident only that our remote forebears adopted two of the strategies just listed: versatility, and use of the trees for shelter. The rest are just a best guess, based on what related forms do in similar circumstances. But even if this listing falls short of a characterization, there is a compelling case to be made that even today, humbling as it may be, the World's Top Predator bears the scars of its lowly beginnings as favored items on the menu of a whole array of carnivores.

THE INTERIOR WORLD

We are beginning to form a picture of the australopiths, hazy and incomplete though it might be. They were small-bodied upright bipeds, with considerable tree-climbing abilities: creatures that moved between the forest and more open environments where they would have lived in large social units for protection. They had complex social lives, based on intensive cooperation and a form of sociality expressed by groups embracing many individuals of each sex and age. They were highly vocal; and, by analogy with living apes (presumably the best parallel in this respect), they would have had a vocabulary of several dozen distinct utterances, each expressing one of a range of different situations or emotional states. We can confidently say that these remote forebears were generalist omnivores, exploiting what both the forest and the savanna had to offer; and in this way they differentiated themselves even from modern savanna apes, who seek forest-type resources wherever they may be. The archaic hominids lived at least part time in a dangerous and challenging environment. And though they had brains not much bigger than those of apes of comparable body size, at some point they began to make stone tools and carry around the materials necessary for their manufacture, indicating a level of cognitive complexity beyond what any ape has yet demonstrated. The tools and the carcasses they dismembered provide the first evidence we have for the consumption by hominids of animal fats and proteins, although by analogy with chimpanzees it seems reasonable to conclude that flesh-eating
and meat-sharing may have been an established behavior long before.