Escápula

Finally, the genetic heritage of every species contains certain elements that are unique to it alone. As we have seen, many of the most important attributes of our species represent an intensification of attributes that are important to mammals in general and primates in particular. Thus, while nearly all mammals, especially primates, rely heavily on social organization, learning, and communication as mechanisms of adaptation, and these give rise to powers of personal recognition and a sense of self-identity, these traits are far more pronounced in human popu- lations. But why, we may ask, should this be true, and how did humans come to occupy the unique niche they do in the global ecosystem?

The answers will probably never be fully known, but recent research on the origins of the hominids provides a number of clues. For example, it now appears that one of the first major biological innovations in the hominid line was the shift to bipedal locomotion. This occurred long before the growth in cranial capacity or any other identifiable morphological change (e.g., Maryanski and Turner, 1992: 69). Bipedal locomotion is thought by many to have been associated with a shift in habitat from arboreal conditions to more open grasslands where upright pos- ture provided a selective advantage both in the search for food and in defense (i.e., by providing a larger visual field). More significant, however, an upright stance freed the already dexterous primate hands for new kinds of activities, and these provided a selective advantage to individuals with good hand-eye coordination and greater intelligence, thus setting in motion evolutionary trends with far-reach- ing behavioral consequences.

The most important trend may well have been the enhanced potential for toolmaking and tool-use. Modern research has shown that humans are not unique in their ability to make and use tools. But this research also makes it clear that humans are indeed unique both in the subtlety, complexity, and effectiveness of the tools they make and in the degree of their dependence on them. Whereas tool- use is an occasional and infrequent activity among chimpanzees, and of minor importance as an adaptive mechanism, it is a constant and ubiquitous activity among humans and a vital adaptive mechanism. Thus, the shift to bipedal loco- motion seems to have stimulated early hominids to cross a critical evolutionary threshold that drastically altered the subsequent course of hominid history.

Another consequence of bipedal locomotion may well have been a strength- ening of the social ties between adult males and females, a relatively weak link in most other primate social systems (Maryanski and Turner, 1992: table 2). Ar- chaeological evidence indicates that from an early date hominids used their hands

The Biological Foundations of Human Societies 41 and arms to transport meat from the places where it was obtained to residential campsites elsewhere. As this is not the typical primate pattern (since primates usually eat food wherever they find it), the practice of these early hominids sug- gests that the meat was shared. If this inference is correct, it indicates that bipedal locomotion reinforced the basic thrust of mammalian and primate evolution in an important way, and contributed significantly to a key element in the develop- ment of the social foundation on which the subsequent growth and elaboration of human societies depended.

While much of the foregoing remains speculative, the record shows clearly that over the course of the last 4 million years, the hominids grew physically larger overall, with the growth in cranial capacity being especially pronounced. This trend seems not to have run its course until the emergence of Homo sapiens in the last several hundred thousand years.

The most important consequence of these developments was a major break- through in hominid powers of communication. In the earliest days of their his- tory, there is no reason to believe that the hominids differed appreciably in this respect from modern chimpanzees and gorillas, their closest kin in the animal kingdom today. In other words, the earliest hominids probably possessed a com- plex repertoire of signals (i.e., mechanisms of communication whose meaning is genetically fixed) but lacked the power to create or use symbols (i.e., mechanisms whose meaning is established by their users). Somewhere in the evolution of the hominids, however, symbol-creation and symbol-use got their start. Where and when this happened is still anybody’s guess (Washburn, 1978), but it was almost certainly a gradual process requiring substantial development of the cerebral cor- tex.

Eventually, however, symbol systems became far more complex and as this happened the foundation was laid for a radically new mode of evolution. For the

first time in evolutionary history, a species had the capacity to acquire vast stores of information that were separate and distinct from the information contained in its genes. Learning and communication could now become tools to be used in a lim-

itless process of information acquisition and cumulation, something never before possible.

With this new power at their command, the stage was set for the cultural explosion that has carried humans to the position of dominance they now enjoy in the world of larger vertebrates. Symbol systems made it possible to translate individual learning of every kind into forms that could readily be shared with others and, ultimately, with the entire human population. With this new “tool,” human societies were able to expand into habitats previously closed to them, ex- ploit new resources, and grow in numbers as no large-bodied animal had ever done before. Furthermore, they could now develop patterns of life as diverse as those of different species, while still preserving their genetic unity, something else never before possible in evolutionary history.

Figure 3.3 describes graphically the basic determinants of the phenotypic properties or attributes of human populations. The model is the same as Figure

3.2 with two important exceptions. First, the relatively weak and limited direct link between the phenotypic properties at Time 1 and Time 2 has been enor- mously strengthened. And, second, the sociocultural environment has been added as one of the basic determinants of the phenotypic properties of human popula- tions. In other words, the model has also been modified to take account of the enormous influence that human societies exert on one another.