Human Groups as Units of Selection

摘要

Holistic thinkers throughout history have ' compared human societies to single organisms. Modern scientists have tended to dismiss the organismic view of society as a misleading metaphor, but a recent article by anthropologist C. Boehm, director of the Jane Goodall Research Center at the University of Southern California, suggests that it may contain an element of truth (1). Boehm's article appears in a supplemental issue of The American Naturalist devoted to the subject of multilevel selection (2).Natural selection within a single population can explain the functional design of individuals, which causes them to survive and reproduce more successfully than their neighbors. However, this process cannot explain the evolution of altruistic behaviors,which are good for the group but, nevertheless, decrease the relative fitness of the altruistic individual within the group. Even behaviors that benefit the group as a collective, at no cost to the individual, are merely neutral from the standpoint of within-group selection. Darwin was, aware of this problem and proposed that natural selection can operate at more than one level of the biological hierarchy. Altruists may be less fit than nonaltruists within a single group, but groups of altruists are more fit than groups of nonaltruists. Groups can evolve into adaptive units if the process of group selection is sufficiently strong, relative to the process of individual selection.