A mechanism originally proposed to account for the evolution of altruism in social groups of animals. It was suggested by the British ethologist V. C. Wynne-Edwards (1906–97) in 1962, and arose from his observations that individual animals often expose themselves to danger (for instance by warning of predators) or forgo reproduction (as with worker bees in a colony) for the greater good of the group as a whole. Hence, groups containing altruistic individuals would have some selective advantage over groups lacking such members. This conflicts with Darwinian orthodoxy, which views natural selection as operating strictly on individuals. More recently, group selection has been reformulated by the biologist E. O. Wilson (1929– ) into multi level selection theory, which proposes that selection acts simultaneously on many levels, from cells through individuals to groups. However, proponents of the theory of kin selection regard this as a more plausible explanation of apparently altruistic acts, and the controversy continues.