R. Trivers

The evolution of reciprocal altruism: bibliographical excerpts

"During the Pleistocene, and probably before, a hominid species would have met the preconditions for the evolution of reciprocal altruism: long lifespan; low dispersal rate; life in small, mutually dependent, stable, social groups (Lee and DeVore, 1968; Campbell, 19660; and a long period of parental care. It is very likely that dominance relations were of the relaxed, less linear form characteristic of the living chimpanzee (Van Lawick-Goodall, 1968) and not of the more rigidly linear form characteristic of the baboon (Hall and DeVore, 1965). Aid in intraspecific combat, particularly by kin, almost certainly reduced the stability and linearity of the dominance order in early humans." (Trivers, R. (1971) The evolution of reciprocal altruism. Quarterly Review of Biology 46: p. 45)

human evolution