Natural selection — the differential propagation of heritable traits arising because individuals bearing advantageous variants have higher fitness, defined as total ability to pass genes to offspring through both survival to reproductive age and reproductive success — is not the only mechanism by which allele frequencies change in a population. Group selection holds that traits benefiting the population as a whole can be favored even when they do not raise the bearer's own fitness, a possibility that follows from the principle that populations, not individuals, evolve; it accounts in particular for traits expressed after reproductive capacity ends, which individual-level selection cannot directly favor. Artificial selection differs from both in its selective agent: an external chooser deliberately determines which traits are propagated, replacing probabilistic differential survival with directed choice. The topic belongs to evolutionary biology, extending the theory of selection beyond its individual-level formulation.
Natural selection — the differential propagation of heritable traits arising because individuals bearing advantageous variants have higher fitness, defined as total ability to pass genes to offspring…