What is genetic drift?

Genetic drift refers to the random fluctuations in allele frequencies within a population from one generation to the next due to chance events. This phenomenon is particularly significant in small populations, where the random nature of mating and survival can lead to large changes in genetic structure over time, even if no specific selective pressures are acting on the alleles.

Unlike processes such as natural selection, which favor the survival and reproduction of organisms with advantageous traits, genetic drift operates independently of fitness. For example, if a few individuals happen to carry a rare allele, and they contribute disproportionately to the next generation's gene pool, the frequency of that allele can increase or decrease purely by chance. This randomness can lead to the fixation or loss of alleles, reducing genetic variation over time.

Understanding genetic drift is crucial in evolutionary biology, as it can have profound implications for the evolutionary trajectory of populations, particularly those that are small or isolated. It also plays a role in concepts such as the founder effect and population bottlenecks, where a small subset of a larger population leads to a significant genetic shift.