What does genetic drift refer to?

Genetic drift refers to the change in frequency of gene variants within a population due to random sampling processes, particularly in small populations. This phenomenon occurs when certain alleles become more or less common purely by chance, leading to fluctuations in allele frequencies over time. Unlike natural selection, which involves differential survival and reproduction based on advantageous traits, genetic drift does not favor any specific allele; instead, the shifts in frequencies are often due to random events, such as which individuals happen to survive to reproduce.

For instance, consider a small population of butterflies where a random event causes a few individuals to survive and reproduce. If all surviving butterflies happen to carry a particular variant of a gene, that allele's frequency may increase in the next generation simply through chance. This can lead to a loss of genetic diversity within the population, particularly if certain alleles are lost entirely.

This process is crucial to understanding population genetics and evolutionary biology, as it highlights how randomness can shape genetic diversity in populations, independent of natural selection pressures.