Group Selection

In evolutionary biology, the theory of group selection posits that natural selection occurs at the group level, and thus can influence the evolution of social traits. Natural selection favors traits that confer a fitness advantage to their bearers in the overall population. In social organisms, traits may be favored in the population by bestowing advantages at the group level. For example, when comparing fitness differences within groups, selfishness always beats altruism. However, as selfishness increases in frequency within a group, the average fitness of a group member will plummet in the overall population compared to individuals within more altruistic groups. Therefore, if groups vary in the proportion of altruists, then the differential contribution of groups to the total gene pool can favor altruism despite their selective disadvantage within each group.