Why did human evolution diverge from that of our closest primate relatives? What can studying apes tell us about early human social structures? What actually makes us different? In the richly illustrated and referenced Apes and Human Evolution, University of Chicago Professor of Anthropology and Evolutionary Biology Russell Tuttle synthesizes virtually all we know about such questions to produce an authoritative history of the evolution of us. Below, Tuttle outlines some of the major topics addressed in the book, which he’ll be presenting at Chicago’s Seminary Co-Op Bookstore on March 20th.
In Apes and Human Evolution, I argue that since the 19th-century evolution revolution, theories of human evolution have been biased by folk beliefs about the meaning of individual, sexual and group differences in appearance and customs and by world events, like warfare, and personal experiences of theorists. As apes became subjects of detailed study their behavior served variously to reinforce or refute notions of close similarity between them and us.
Over the past 45 years scientists who trained in programs devoid of anthropology have developed models that emphasize increasingly close affinity between African apes and humans. Some of them claim that chimpanzees are actually people (Homo troglodytes and Homo paniscus) or that people are somewhat more cultured chimpanzees (Pan sapiens). Such claims, abetted by popular books and other media, exemplify poor evolutionary anthropology and are offensive toward the very communities and heads of state to whom we must appeal for scientifically informed preservation of apes and their habitats.
Although the old argument about which nonhuman primates are closer to humans has settled on the apes, many puzzles remain regarding the extent to which we can draw on them as models for specific aspects of our variable genomes, morphology and behavior. Rare major and many minor fossil discoveries underpin phylogenic models of primate evolution over a span of geologic time greater than sixty-five million years, but small samples of fragmentary specimens and very patchy spatiotemporal representation usually limit their informational value. Our Linnaean family, the Hominidae, contained a notable number and variety of species that is difficult to organize into phylogenic lineages, only one of which terminated in modern Homo sapiens.
The most salient difference between humans and apes is that Homo sapiens occupies a symbolic niche—virtually everything we say, do, create and make is consciously or unconsciously dependent upon symbols—while wild apes function quite cleverly in forest, woodland and occasionally more open habits without reliance on lexical symbols. Although apes and many other animals probably think about proximate situations, humans have beliefs about phenomena and relationships. Further, humans have social and moral codes, while apes are probably amoral. Their survival and that of our species ultimately depends upon us.
The emergence and further evolution of symbolic thought, particularly language, in Homo sapiens, and its underpinnings in the brain constitute one of the grand mysteries that await empirical resolution by scientists from many disciplines. Ingenious laboratory studies revealed that some great apes learn to communicate with humans and one another on par with human 2-year-olds via sign language and non-iconic symbols; however, thus far their natural vocalizations offer fewer clues to a system of communication that might have been used by early hominids. There is notable disagreement about when fully human language emerged and the sequence of events that culminated in it.
Unlike human hands, which are free of obligate locomotive functions, ape hands are evolutionary compromises serving various locomotive activities, grasping and fine manipulation, including tool making and use. Their hands are highly sensitive, which allows them to feel fruits for ripeness, to manipulate tiny objects and to engage in social grooming. Fossil hominid hands dating more than 1.5 million years old retain features that would facilitate arboreal climbing.
Apes are a rich resource for theorists who model emergent hominid and early human social structures. Gibbons are attractive to those who believe that human monogamy is deeply rooted in the past. Orangutans are usually ignored because adults do not form stable groups. Gorillas and especially chimpanzees are favorites of persons who emphasize male dominance and aggression, while bonobos are preferred by modelers who view our apish ancestors living in quasi-egalitarian societies with notable female agency. In fact, humans are quite unique in possessing a great variety of social systems based on who is to be considered kith and kin, even embracing persons who are not genetically related. The capacity to love others enduringly and to share food and other objects over a wide network of beings sets us apart from the apes.
Apes display highly diverse repertoires of arboreal and terrestrial locomotive behaviors that inspire models on the evolution of human anatomy. Modelers of the evolution of human obligate erect bipedal posture employed living apes to exemplify precedent behavior and anatomy upon which various selective forces acted to produce the human form, viz., below branch arm-swinging and knuckle-walkers, closely resembling chimpanzees. Instead, I propose that a small-bodied vertical climbing, bipedal branch-running ape is a more likely model because similar lower limb mechanics are involved in vertical climbing and human bipedal walking.
The daily food quest and need for secure lodge trees affect the ranging patterns of all ape species. They prefer fruits; however, during fruit shortages they are remarkably versatile in accommodating to a wide variety of vegetal and animal foods. All great apes build arboreal nests at night. It is highly likely that like them, small groups of early hominids also reclined on tree platforms at night and used trees to escape from predators during the day. Only after they learned to control fire, build shelters and employ effective weapons might they roam more freely over large expanses of open space and populate the globe.