How does genetic drift occur?

Genetic drift occurs primarily through random changes in allele frequencies within a population, particularly in small populations. This process is independent of natural selection, which operates through differential survival and reproduction based on advantageous traits. In contrast, genetic drift can lead to the loss of alleles or fixation of alleles simply due to chance events, such as random mating patterns or catastrophic events that affect population size. Over time, these random fluctuations can significantly influence the genetic composition of a population, leading to divergence between populations and a decrease in genetic variation.

Understanding genetic drift is essential because it emphasizes the role of chance in evolution, highlighting that not all evolutionary changes are driven by the adaptive advantages that natural selection promotes. This concept further illustrates the unpredictable nature of genetic changes in biological populations.