Some day, scientists might well have enough fossil and genetic data to prove the exact paths that evolution took. Bones and molecules will ultimately show what evolved. But they’re not as useful regarding how evolution occurred. To understand the reasons behind evolution in recent times, anthropologists are now studying the behavioral patterns of our closest living relative—the chimpanzee.
Chimp Traits How do we know that chimps are so closely related to humans? Because the fossil record and the genetic markers say so—pretty clearly. Laboratory studies of protein molecules are now routinely used to measure differences in the kind and sequence of amino acids among many animals. Comparisons of human proteins with those of, for example, a horse, a rat, or a frog show large differences in the number and order of their amino acids. But comparisons of human and chimp proteins show very few differences: The average human protein is >98% identical to that of chimpanzees, making humans as close to chimps as, say, a fox is to a dog. Some proteins, such as hemoglobin (blood), have exactly the same numbering and ordering of amino acids in humans and chimps. Thus of all the members of the ape family, chimpanzees have a genetic makeup closest to that of humans. Bonobos (sometimes called pygmy chimps), poorly known members of the ape family and one of the last large mammals to be found on Earth less than a century ago, may have a genetic profile even closer to ours—and a fraternal behavior that rivals ours as well.
Chimpanzees also have a life-style closest to our own. (Gorillas outwardly resemble humans more than do chimps, but their genetic structure is additionally different and their daily habits much different.) More than any other animal, chimps apparently resemble the ancestor from which other apes as well as humans ascended. By studying modern chimps, then, behaviorists discern a little bit of what life was like for our ancestors several million years ago. Present attributes, adopted environment, and the social conduct of chimps might all tell us something about the evolutionary events that led to the divergence of humans from our common ancestor, but of course chimps too have since evolved.
Many attempts have been made to study the lifestyles of caged chimps in zoos. But each time it soon became clear that the intricacies of ape society can likely be unraveled only in the wild. And “the wild” means just that; chimps and their ape relatives live in remote places, for their niche must differ from that of humans, lest all of us be unable to coexist. Most chimps are shy and unaccustomed to being watched by intruding humans. Many inhabit nearly inaccessible mountain retreats, while others stay up in the treetops of thick jungles. Reaching the appropriate places often proves tricky for anthropologists, as do the problems of which chimp properties to study and how to interpret the data once collected.
Organized fieldwork has now shown that chimps and other semi-bipedal (two-legged) apes are clearly more intelligent than monkeys and other quadrupedal animals. Bipedalism permits erect posture, thereby freeing the hands, and the resulting manual dexterity in turn provides a wealth of new opportunities for living. To give but one example, as shown in Figure 7.11, the uncanny handiwork of modern chimps is evident when they routinely fashion an implement by stripping leaves from a tree branch, insert it into a hole in a termite mound, then remove it carefully and systematically lick off the termites clinging to the branch.
Which was the cause and which the effect—ability to stand on hind legs or capacity to work with the hands—is currently unresolved. Instead of the explanation just given, namely, that erect posture promoted toolmaking, the cause and effect may have been reversed. The need to manipulate food may have helped human ancestors to become increasingly upright over the course of millions of years. Perhaps these two critically important evolutionary traits are so hopelessly intertwined as to preclude knowing which was the original instigator. More likely and more complicated, each trait might have contributed to the other in an intricate way: Primitive bipedalism may have led to a small amount of manual dexterity, after which increased hand use accelerated the change toward more erect posture, which in turn fostered the development of even more complex tools, and so on. This is an example of positive feedback, whereby the advancement of one attribute stimulates another, after which the second reflects back on the first, and so on back and forth, thereby causing further and faster mutual development of both. Such feedback reinforcement was probably a key mechanism in the optimization of many traits throughout prehuman evolution.
The physiology and habits of modern chimps imply many things about our australopithecine forebears. Chimps are small enough to get around in the trees, yet large enough to ward off most predators while on the ground. They can be especially formidable when traveling as part of a large group, as they often do. Chimps’ favorite food is fruit, especially ripe figs, though they also eat meat and birds’ eggs, as well as small snakes, lizards, and insects. They are known to experiment occasionally with different foods, revealing some innate curiosity. To be sure, basic chimp intelligence is evident in many ways such as when they use twigs as tools, bang rocks to smash objects, wave branches overhead to intimidate enemies, and employ grass as a sponge to hold water. Chimps have an open, free society, enabling them to try many new things.
Perhaps even more interesting than their expressions of curiosity are reports that chimps may show some degree of self-awareness. For example, when exposed to mirrors, most chimps rapidly progress from treating the image as if it were another chimp to recognizing it as themselves. They seem to have a sense of “self,” perhaps even a primitive cognition sufficient to know who they are. Once thought to be inherent only to humans, self-recognition might be an integral part of the intellectual repertoire of these remarkable apes.
Chimps are also observant copycats. The young learn readily from their elders, as well as from their human trainers. Though their lack of vocal equipment prohibits them from speaking, a few chimps can now communicate symbolically with humans by means of sign language routinely used by deaf people. Some chimps have even displayed symbolic gestures to communicate with other chimps. Such chimp-to-chimp conversation implies that their intelligence incorporates much teaching and learning ability, meaning that chimpanzees are probably a lot smarter than anyone thought a generation ago. What’s more, it may be unfair to label chimps mere copycats. Parrots and seals can also imitate, but there’s a difference here: Other animals can be trained to imitate, whereas chimps seem to have a childlike ability to learn by imitation.
Chimps are furthermore sociable, though in a highly stratified way. All groups of chimps show a clear social hierarchy, comparable in many ways to today’s human groups, whether in the military, business, academic, industrial, or political sector. One or a few males usually dominate a host of subservient chimps, thus ensuring some stability rather than the constant infighting that might otherwise engage a completely normless society. This social structure doesn’t, however, seem to stifle their curiosity or amicability. As implied by Figure 7.12, some chimps are forthrightly altruistic, sharing food with other members of their group, though most are not. Chimps are thus not wholly self-centered, as implied by earlier studies; some occasionally show affection for others in their group, though seldomly for chimps who aren’t their immediate offspring.
Chimpanzee society is so complex that ~15 years are needed for a newborn chimp to reach maturity. Like human adolescents, young chimps take many years to learn everything required to become a full member of their social organization. In a certain sense, young chimps are schooled by their parents.
Does that mean that today’s chimps display the rudiments of culture? Watching them in the wild hammering a shelled nut with a rock, are we seeing the roots of human culture millions of years ago? The answers involve semantics again: Some biologists regard culture as including uniquely human skills such as language, music, or art, but others regard it more simply as any behavior learned from fellow group members of a population rather than inherited through genes. This latter, more general interpretation might then include songs of birds and calls of whales. Although culture was for many years considered unique to the human species, evidence is growing for socially learned traditions elsewhere in the mammalian kingdom, and not just among chimps and bonobos, but also including birds, monkeys, rats, and maybe even fish. But do all these species really learn from each other, with behaviors passed from generation to generation rather than discovering them on their own? True culture, like much else in this CULTURAL EPOCH, is often more tricky—or at least more emotional—to address than some of the earlier, more remote issues of the GALACTIC and STELLAR EPOCHS.
That chimps really do learn in their formative years demonstrates that environment plays a large role—at least among modern chimps. Other completely unrelated, insect species, such as bees and ants, also have organized societies, but they don’t really learn. Environment seems to have little bearing on insect knowledge. Laboratory studies show them lacking freedom of individual expression while going about their daily business; insects display little, if any, of the curiosity needed to try new things. Consequently, while insect society is most definitely (and impressively) organized, insect behavior is not overly complex. The social organization of insects is more rigidly controlled, being almost entirely programmed by genes.
Because chimps learn so well, behaviorists cannot easily tell how much innate smarts they really have. What part of their intelligence derives from their biological genes and what part from their cultural environment is simply unknown. We are now in the midst of an ongoing debate concerning the relative importance of the gene and the environment—a debate regarding not only the development of intelligence in chimps. The gene-environment controversy affects all aspects of living beings, especially the cultural evolution of humankind.
Genes and Environments The extent to which intelligence is genetically preprogrammed, in contrast to it being environmentally endowed, remains controversial. The issue of gene (nature) versus environment (nurture) has triggered an emotional debate for the past quarter century, indeed has forged a whole new interdisciplinary field of research. Sociobiology—the study of the biological basis of social behavior—aims to know the social instincts within any community of life forms by appealing to the basic principles of psychology, genetics, ecology, and several other seemingly diverse disciplines. A principal goal of this research seeks to identify the inheritable traits that mold societies, and secondarily to unravel the degree of importance between competition and cooperation.
Sociobiology expands the study of biological evolution to include society. Also known as social evolution or evolutionary psychology, whatever it’s called it’s bound to be a key feature of the CULTURAL EPOCH. In cultural evolutionary terms, the fitness of an individual is measured, not just by her own success and survival, but also by the contributions made to the success of her relatives, namely, those who share some of her genes. These contributions are often self-sacrificing ones and can be classified under the general heading of altruism—unselfish devotion to the welfare of others—a fancy word for love. Whereas the catchphrase for classic biological evolution is the oft-stated “survival of the fittest individual,” that for sociobiology and cultural evolution would be something like “preservation of an entire society.”
Competition isn’t the sole driving force in evolution; cooperation is also a factor, at least for biological and cultural evolution, and at least to some degree. That much was clear regarding the emergence of multicellular creatures from single-celled organisms ~1 billion years ago, as well as during symbiosis that gave rise to eukaryotes billions of years before that, both noted in the previous BIOLOCICAL EPOCH. Even earlier, mutual aid might have been essential for chemical evolution if replication of prebiotic molecules was helped along by catalytic surfaces at the time of life’s origin. Advanced life, especially insect societies, such as among ants and bees and including several other animals, also seems to be partly founded on altruistic behavior, meaning that for them cooperation plays a significant role. For instance, wild dogs regularly regurgitate meals in order to feed their young; some species of birds postpone mating to help rear their siblings; “soldier” termites explode themselves, spraying poison over armies of ants, whenever a termite colony is attacked. This behavior is always the same, regardless of where and when the dogs, birds, or termites happen to act. They perform like programmed machines.
Behavior so rigid and uniform has prompted many biologists to argue that it might be exclusively determined genetically, at least among the “lower” forms of life. If so, then each trait, act, or duty likely has its own gene or genes, which are inherited in much the same way as body size, shape, and structure. The principal role of these behavioral genes is to preserve the species. Even while imprisoned within the bodies of life forms, the genes control all. Extremely interpreted, life forms exist for the sole purpose of perpetuating the genes—the selfish and unaltruistic genes.
Sociobiology remains controversial mostly because its proponents argue that its central tenets can be extended from insect societies to the societies of “higher” life forms, including humans. Problems always arise when scientists—or anyone really—make grandiose pronouncements about our own species. Trouble starts because human nature isn’t always what we think proper. Bias and value judgments sneak into science, perhaps an inevitable consequence of getting closer to studying ourselves along the arrow of time. The main issue is this: To what extent does human behavior depend on the underlying genes? Which has the dominant influence over the actions of humans, nature or nurture? This is the root of the controversy—human understanding of human affairs.
Researchers generally fall into two groups, both conceding that environmental factors play the greater role in human behavior. One faction maintains that environment is virtually the only important influence: Behavioral differences among humans are strongly governed by social, cultural, and political factors—meaning that human control of human behavior is possible. The other group contends that genes are of considerable import: Genes may weigh only 10% in their contest with the environment, but enough for many traits (aggression, envy, sympathy, love, fear, intelligence, among others) to be partly predestined in humans. If so, then societal changes in human behavior are limited because much of behavior is biologically dictated by the genes. This second school of thought presumes that, for example, the behavior of humans who go hungry to feed their children, or the behavior of persons who risk their lives to save a drowning swimmer, is not the result of free will. Instead, paralleling an insect’s desire to preserve its own species at all cost, such behavior is an unconscious reaction built into and dictated by our genes to ensure survival of our own kind—a nepotistic process known as kin selection among interacting individuals who are genetically related. Cooperation then comes to be seen as costly to individuals, but potentially beneficial to groups.
Whichever ideas of sociobiology prove valid, it will be important for psychologists and psychiatrists to pay heed. The way people act may be, to some degree, biologically predetermined. Sociologists should also take note, for sociobiology may someday give them quantitative methods by which to test their frequently unsupported assertions. Indeed, economics, law, and politics might eventually become part of the interdisciplinary subject of sociobiology, and in turn part of the more inclusive, transdisciplinary worldview of cosmic evolution.
Society, Good and Bad Love, altruism, kinship, and curiosity are attributes associated, not only with humans, but also with chimps and probably other animals as well. Many contend that these notable qualities of goodwill are less apparent in chimps than in humans, but a glance at the daily newspapers can create doubts.
Not to imply that chimps are nice and gentle all the time; vegetarian pacifists they’re not. Chimps do resemble humans in yet another way, namely their occasional desire to exert unnecessary aggression. Some conflict within and among species is a normal, perhaps even essential, ingredient of biological and cultural evolution. “Nature red in tooth and claw” may sound politically incorrect among idealists in today’s revisionist society, but competition and exploitation are part and parcel of any evolutionary setting. Cooperation and mutualism work more subtly and only to limited extent alongside natural selection, especially as regards individual reproductive success. Even when life forms do clearly cooperate, it’s often done only when in their own best interest. Without some aggression in the guise of competition, few if any species could adapt to changing environments. Reactive aggression probably has deep biological roots, yet unprovoked aggression would seem to be another thing entirely.
Field studies in Tanzania illustrate how some chimps occasionally murder other chimps for no apparent survival-related reason. Premeditated, gangland-style attacks were directed by a large group of male chimps on a smaller group of males and females that had previously broken away from the larger group. Over the course of five years, each member of the splinter group was systematically and brutally beaten. All died. Only young males initiated the attacks, which occurred only when the victims were isolated from the others. Hands, feet, and teeth were often used by the attackers, though sometimes field-workers noticed stones being deliberately thrown. The hope, of course, is that comparative studies like these will uncover the reasons behind not only chimp misdemeanors but human belligerence as well, perhaps helping to guide the future survival of the human species, which, it would seem, can no longer tolerate intraspecies aggression.
Despite lingering controversy over details, behavioral studies of modern chimps have aided greatly our understanding of the ascent of humans. As ape-like animals resembling chimps nearly 10 million years ago began leaving the forests for the savanna (or perhaps it was more that the forests left them as an oncoming ice age made parts of Africa cool and dry), they were probably forced by environmental circumstances to become more sociable in order to survive. The origins of our social organization may well have been shaped by the new, harsher conditions in the open plains, where there would have been less food, reduced protection, and thus greater need for group cooperation—or was it everyone for himself, hence unfettered competition?
These hardships nonetheless gave our ancestors a chance to experiment and to learn as their sights and experiences grew over the course of millions of years. The parochial mentality of forest-living animals was replaced by the wider perspective of our plains-dwelling ancestors. Of much consequence, this suddenly larger world created pressures to evolve bigger brains capable of storing a dramatic increase of raw information.
Change from life in the trees to that in the plains was a renaissance of sorts that likely took a million years or more. Yet once it commenced, the race was on—a race to inhabit entirely new niches, to develop whole new ways of life, and eventually to become technologically intelligent.