Genetic Drift

Genetic drift is the change in the frequency of a particular gene variant within a population that occurs purely by random chance from one generation to the next, rather than through natural selection acting on any advantage or disadvantage the variant confers. The concept was developed chiefly through the work of population geneticist Sewall Wright beginning in the late 1920s and especially the early 1930s, as part of his broader mathematical modeling of evolution within finite populations, and it forms one of the core mechanisms of the modern evolutionary synthesis alongside natural selection. Genetic drift has the strongest relative effect in small populations, where chance fluctuations in which individuals happen to survive and reproduce in a given generation can more easily and rapidly shift a gene variant's frequency, potentially even causing it to become fixed throughout the population or to disappear entirely regardless of whether it is helpful, harmful or neutral. Genetic drift is understood as a fundamentally distinct evolutionary mechanism from natural selection, since it acts randomly with respect to a variant's fitness effect, and the two mechanisms are now generally treated together as complementary forces shaping the genetic makeup of real populations over time.