Theories of kin and group selection: A population genetics perspective

Abstract

The elucidation of the evolution of altruism has been described as “the central theoretical problem of sociobiology” (Wilson, 1975, p. 3). While altruistic “socially valuable but individually disadvantageous” (Haldane, 1932), traits are by definition necessary for the functioning of semisocial and eusocial insect societies in which workers exhibit reduced fertility (E. 0. Wilson, 1971, p. 4), the significance of altruism to the evolution of social systems in general may be questioned. Nevertheless, if one accepts Wilson’s (1975, p. 7) definition of a society as a group of cooperating individuals of the same species, it is useful to consider the general problem of the evolution of cooperation from the perspective of the “worst” case, in which cooperative individuals incur a cost in fitness in order to benefit other members of the group. The purpose of this paper is to review the major hypotheses which have been advanced for the evolution of altruism under kin selection and group selection, and to attempt to relate the various verbal and mathematical arguments which have been applied to the problem. The theoretical context will be a population genetic one. In this view, the model of evolution is one of gene frequency change; strategy arguments based outside of the dynamical theory of genotype frequency change are not addressed. First, mathematical models of kin selection are surveyed and the results compared to the qualitative predictions proposed by Haldane (1955) and Hamilton (1964a,b). Second, various definitions of group