Mechanistically, gene flow can be quantified to model heterozygosity changes in populations due to the number of migrants, variability of migrants-how deviant are their gene pools relative to the assuming population (usually a function of distance or time), and the impact of the other evolutionary forces. The importance of gene flow as an evolutionary force becomes powerful when it is limited, and limiting of gene flow between taxa or demes is accomplished through the construction of barriers to mating or through isolation mechanisms (generally constrained to geographic and reproductive barriers). In this way it is the balance of gene flow and genetic drift that dictates a population’s ability to maintain genetic variation. As genetic drift functions to push alleles toward fixation, especially in small populations, gene flow works to prevent fixation and to maintain heterozygosity (the presence of multiple alleles at a loci in the defined population). A multifaceted evolutionary force, gene flow is often considered to work in opposition to the other evolutionary forces (although this is context dependent), maintaining genetic and phenotypic homogeneity across subpopulations within taxa. Gene flow is one of the primary mechanisms of evolution, generally modeled along with genetic drift, mutation, and natural selection. Referencing the specific context of transferring genetic variation between populations, gene flow is often used interchangeably with migration, although migration also includes population movement into unoccupied regions, which according to some sources is not considered gene flow.

In anthropology, gene flow more generally refers to allelic change due to movement of individuals from one place to another. Gene flow is a term that describes mechanisms of gene transfer from one population to another.

Gene drift vs gene flow