Issues in human evolution
Richard G. Klein a,1
Author Affiliations
aProgram in Human Biology, Stanford University, Stanford, CA 94305
New discoveries, new methods, and new theories continue to boost understanding of human evolution. Genetics has shown that contrary to what anatomy alone has long suggested, people and chimpanzees are more closely related to each other than either is to any of the other great apes. This finding has forced a change in long-standing taxonomic practice, and specialists now commonly place all of the great apes, including people, in the family Hominidae, previously reserved for people. People, living and extinct, are then separated from the other apes at the tribal level as Hominini, anglicized to hominins (1). This PNAS Special Feature showcases some recent discoveries and ideas on what makes the hominin mind unique, on the environmental backdrop to hominin evolution, on whether early hominin evolution should be characterized as a ladder or a bush, on what ancient DNA tells us about the demographic history of living humans and their closest fossil relatives—above all the Neanderthals—on the extent to which the Neanderthals differed behaviorally from modern humans, and finally on how prehistoric modern humans, following their expansion from Africa 50–40 ka, impacted other species.
In the opening article, MacLean (2) argues that hominins share many features of cognition with other species, particularly the great apes, but that hominin cognition nonetheless remains unique. Thus, like humans, the other great apes can grasp the intentions and desires of others, but only humans routinely use the information for communal or cooperative purposes, beginning around age one. Common chimpanzee males hunt cooperatively, but the spoils go almost entirely to the successful captor, with little or none of the communal sharing that occurs when humans hunt in groups. This uniquely human tendency to collaborate for the good of the social unit largely explains the difference between human culture and what has been called chimpanzee culture. …
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