On the neighbor effect and the evolution of altruistic traits

The long-term effects of natural selection are studied in a large population in which survival and fertility of any individual depend not only on its own genotype, but also on the genetic features of neighboring members of its species-a relatively small group of individuals sharing its social community or immediate geographic vicinity and partially separated from similar groups within the population as a whole. Random drift within such local groups or subpopulations, as well as migration among them are taken into account. Conditions for the evolution of altruistic biological traits, are analyzed. Special consideration is given to natural mechanisms of birth control, and possible implications to human evolution are offered. In agreement with Wright (1945), low demographic mobility proves to be the most crucial factor for the evolution of altruistic traits.