Genetic Drift

Changes in allele* frequency* in a population due to chance events. Genetic drift is caused by some individuals in a population producing more offspring than others. This causes allele frequencies to diverge from the frequencies expected assuming even representation from generation to generation.

Genetic drift is an evolutionary force because it causes changes in the genetic structure of populations over time. However, the changes are not adaptive in the way that changes due to natural selection* are.

The influence of genetic drift increases as population size decreases. In relatively large populations, small random changes in allele frequencies are negligible relative to the entire population. In small populations, changes driven by genetic drift can be significant. In the extreme case, it can result in the complete loss of specific alleles from a population.