Group selection

The theory of group selection has its origins in the writings of Charles Darwin. Today, we understand it to be exactly equivalent to the theory of kin selection, with both theories explaining the same phenomena, yielding exactly the same predictions, and simply splitting up the mathematics of natural selection in slightly different ways. There are two basic mathematical approaches to group selection: (1) levels of selection, which partitions natural selection into that which owes to differential fitness of individuals within groups and that which owes to differential fitness of groups within the population, and (2) contextual analysis, which partitions natural selection into that which owes to the impact of the individual’s phenotype on the individual’s fitness and that which owes to the impact of the group’s phenotype on the individual’s fitness. These are not competing hypotheses, but rather complementary approaches that are appropriate for addressing somewhat different questions. Group selection can give rise to group-level adaptation, that is, the appearance of complex design at the level of the social group, but this occurs only in extreme circumstances where selection acting within groups is negligible.