Masters of the Planet

by Ian Tattersall

  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 hunted, not the hunters; 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 mode
rn 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.

  What made the intellectual leap to stone tool making possible is not something we can hazard with any confidence at this point, although the refinement of motor skills and of higher cognitive functions almost certainly went hand in hand. But the fact that the first stone tools—the first step in an epic transformation—were made by creatures whom we can—with reservations—characterize as “bipedal apes,” inaugurates a pattern that we will see recurring repeatedly over the entire span of hominid evolution: new technologies (reflecting new and more complex behaviors) do not tend to be associated with the appearance of new kinds of hominid. It was old kinds of hominid that started to do new things, even though those new things always seem to indicate a step up in cognitive complexity.

  We will return to the typical hominid pattern of innovation. But first, it might be interesting to ask if we are in a position to form any impression at all of what kind of sense of the world around them—or of themselves—those bold small-bodied bipeds possessed. We can infer a lot about how their lives might have looked to an observer. But did they share with us any aspects of the unique modern human form of inner experience? There is no way to answer this question with any precision; but one thing that we can do is to set an approximate baseline by looking at other organisms and asking what we demonstrably share with them, and by extension with the early hominids.

  One obvious issue to start with is the sense of self. In the very broadest of meanings, every organism has a sense of itself versus the other. From the simplest unicellular creature on, all living things have mechanisms that allow them to detect and react to entities and events that lie beyond their own boundaries. As a result, every animal may be said to be self-aware at some level, however rudimentary its responsiveness to stimuli from outside might appear. On the other hand, human self-awareness is a highly particular possession of our own species. We human beings experience ourselves in a very specific kind of way—a way that is, as far as we know, unique in the living world. We are each, as it were, able to conceptualize and characterize ourselves as objects distinct from the rest of Nature—and from the rest of our species. We consciously know that we—and others of our kind—have interior lives. The intellectual resource that allows us to possess such knowledge is our symbolic cognitive style. This is a shorthand term for our ability to mentally dissect the world around us into a huge vocabulary of intangible symbols. These we can then recombine in our minds, according to rules that allow an unlimited number of visions to be formulated from a finite set of elements. Using this vocabulary and these rules we are able to generate alternative versions or explanations of the world—and of ourselves. It is this unique symbolic ability that underwrites the internalized self-representation expressed in the peculiarly human sense of self.

  In between the two ends of the spectrum, linking the primordial and the symbolic styles of self-awareness, there presumably exists a near-infinite array of states of self-knowledge. Yet because alien cognitive states are among the few things human beings find it impossible to imagine, let alone to experience, any discussion of such intermediate forms of self-knowledge—such as that possessed by our early ancestors—is fraught with huge risks of anthropomorphizing. When we try to understand how other organisms comprehend particular situations, or their place in society, or indeed their place in the world, our tendency is always to impose our own constructs. The temptation is to assume that beings of other kinds are seeing and understanding the world somehow as we do, just not as well or as fully. Yet the truth is that we simply cannot know, still less feel, what it is subjectively like to be any organism other than ourselves, modern Homo sapiens.

  The extraordinary human cognitive style is the product of a long biological history. From a non-symbolic, non-linguistic ancestor (itself the outcome of an enormously extended and eventful evolutionary process), there emerged our own unprecedented symbolic and linguistic species, an entity possessing a fully-fledged and entirely individuated consciousness of itself. This emergence was a singular event, one that involved bridging a profound cognitive discontinuity. For there is a qualitative difference here; and, based on any reasonable prediction from what preceded us, the only reason for believing that this gulf could ever have been bridged, is that it was. And since that extraordinary event self-evidently did take place, the question becomes one of where and how. To answer this, though, we need to establish that starting point. This is no easy task, and how difficult it is in practice is well illustrated by the investigation of self-recognition.

  Back in the mid-nineteenth century, Charles Darwin placed a mirror on the floor between two orangutans housed at the London Zoo. He recorded a variety of reactions made by the orangutans to their reflections, but was vague as to what, if anything, he had specifically concluded from the experiment. There the matter rested for almost a hundred years, until the cognitive psychologist Gordon Gallup, noting that the norm among animals was to treat mirror images as other individuals, carried out a more controlled test. Gallup exposed two juvenile chimpanzees to full-length mirrors for several days, and watched how they responded to the images of themselves they saw reflected. Over this period, self-directed behaviors increased, while social reactions to the mirror images declined, suggesting that the individuals were learning to recognize the images as themselves. The chimpanzees were then anesthetized, and red marks were applied to their faces. Once they were reintroduced to the mirrors, self-directed behaviors intensified, many of them aimed at the marks. In contrast, marked chimpanzees without prior mirror experience failed to respond in this way, suggesting that self-recognition had indeed been learned by the first group during the habituation period. Similar testing of macaques produced contrary results, implying to Gallup that these monkeys lacked the chimpanzees’ capacity for learning self-recognition.

  Since Gallup’s pioneering study, the “mirror test” has become the standard yardstick for self-recognition among vertebrates, and a wide variety of species has been tested. Human beings naturally need to learn mirror self-recognition (MSR) just as the chimpanzees did; but adults to whom sight has been restored do so quickly, and most human infants can manage the trick at 18 to 20 months of age. Young apes develop more rapidly than human children in many respects, but studies building on Gallup’s original have shown that MSR is rare among chimpanzees under eight years old: it is basically an adult ability. By now, MSR has been demonstrated not only in chimpanzees but also in bonobos, orangutans, and gorillas, although not all tested individuals of these species have shown it. Outside the human–great ape group MSR is evidently extremely rare among vertebrates (though elephants, dolphins, and certain birds may display it); and to the extent it occurs, different underlying mechanisms are almost certainly at work than those operating in great apes and humans. But although its expression in apes and humans is almost certainly a unique property of this group, uncertainty still remains as to what exactly MSR is revealing: what it means in terms of the precise aspects of consciousness that the approach explores.

  An alternative avenue to understanding the sense of self in nonhuman primates was thus taken by the monkey researchers Robin Seyfarth and Dorothy Cheney, who adopted the psychologist William James’ distinction between the two components of self-awareness: the “spiritual” (one’s “psychic faculties and dispositions”), and the “social” (knowledge of being one of
many distinct individuals embedded in a group). Like human beings, monkeys are intensely social, and Seyfarth and Cheney looked at how individual vervet monkeys and baboons appeared to understand their places in the social hierarchy. The reasonable assumption here was that a primate cannot exhibit a sense of “them” without also possessing a sense of “I”; and, from looking both at kin relations and at the dominance hierarchies to which the monkeys belonged, Seyfarth and Cheney concluded that they did indeed recognize other group members as individuals, behaved toward them in appropriate ways, and hence appreciated their own individuality vis-à-vis their fellows. This seemed to indicate that on some level they had a sense of the social self.

  On the other hand, this kind of self-awareness was clearly different from that of human beings. For, while they are certainly able to behave appropriately in complex social settings, vervets and baboons are, as far as one can tell, unaware of the knowledge that allows them to do so. In Seyfarth and Cheney’s words, they “do not know what they know, cannot reflect on what they know, and cannot become the object of their own attention.”

  No observer would deny that great apes possess more complex cognitive and behavioral repertoires than monkeys do. Still, it is far from clear just how far they exceed them in these last respects, and particularly in the ability for self-reflection. Some great apes, like our friend Kanzi, are highly adept users of symbols in experimental situations. They can recognize and respond precisely to words and even to combinations of words, and they can choose visual symbols adroitly on a computer screen. But whether this means that they are also able to manipulate such symbols mentally in such a way as to produce objective images of themselves is doubtful. In general, the apes’ use of symbols seems to be additive: they can comprehend short strings of concepts (“take,” “red,” “ball,” “outside”), but they do not recombine them according to mental rules to produce new notions: ideas of the possible, rather than of the observed. The chimpanzee manner of dealing with symbols is thus is inherently limited, since lengthening lists of symbols rapidly become confusing, and ultimately meaningless.