Changes in gene flow between adjoining groups

Gene flow can be defined as the transferring of alleles that result from emigration, immigration and migration of individuals between populations. Very few populations are completely isolated from each other, and so generally, migration occurs both in and out of the population. Migrating individuals will either add or remove alleles from any given population due to leaving (emigrating from) or joining (immigrating to) a population. One example of gene flow in action is the increasing the B blood group in Indigenous Australians, which occurred as a result of individuals migrating in from Asia and Europe, increasing the frequency of the allele.