Genetic drift

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Genetic drift is the change in the frequency of an existing allele in a population due to chance. Genetic drift may cause alleles to disappear completely and thereby reduce genetic variation. It can also cause initially rare alleles to become much more frequent possibly leading to fixation where the initially rare allele displaces all others. In the middle of the 20th century, vigorous debates occurred over the relative importance of natural selection versus neutral processes, including genetic drift. Ronald Fisher, who explained natural selection using Mendelian genetics, held the view that genetic drift plays at most a minor role in evolution, and this remained the dominant view for several decades. In 1968, population geneticist Motoo Kimura rekindled the debate with his neutral theory of molecular evolution, which claims that most instances where a genetic change spreads across a population (although not necessarily changes in phenotypes) are caused by genetic drift acting on neutral...

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