A recent article in the New York Times* surveys a range of recent studies that compare human beings with lower primates, such as chimpanzees. It turns out that one of the biggest differences is our ability to collaborate and to form social networks. As anthropologist Kim Hill says,
Humans are not special because of their big brains. That’s not the reason we can build rocket ships–no individual can. We have rockets because 10,000 individuals cooperate in producing the information.
One body of research compares mating patterns and kinship in chimpanzee bands and in early human tribes. The evolutionary story is a bit complex (as outlined in Dr. Bernard Chapais’ 2008 book Primeval Kinship), but basically, human beings mate in a pair whereas with chimps, the alpha male dominates all of the females, and the females mate promiscuously with many males, making it unclear who the father is (intentionally, so that none of the males will kill any of the infants). The pair bond of the humans made it much more obvious who your direct relatives were. And this made social relationships with nearby tribes much more complex; with chimps, other tribes are uniformly treated with hostility (because chimps cannot recognize relatives due to high promiscuity). But with human beings, some of the people in the neighboring tribes are your relatives. This ratcheted up the need for social awareness, and led to complex networks of alliances and collaboration.
A second body of research compares human and chimpanzee infants. Professor Michael Tomasello has shown that young children have an ability called “shared intentionality,” the ability to form plans with others to complete a joint task (in his book Why We Cooperate). Children, but not chimpanzees, can point to objects to convey information; and, children can figure out what someone else wants just by watching their eye gaze, which chimps cannot do. And get this: the white portion of the eyes for a human being is three times the size of other primates, which allows us to see where other people are looking. Chimpanzees infer gaze direction by looking at another’s head; but human infants do it by watching eyes.
(Also note: Bernard Chapais’s related article in Science magazine, 11 March 2011, Vol. 331, p. 1276)