Another process that changes the gene pool of a population is the flow of genes from neighboring populations. The genetic composition of any community of individuals, except those living in total isolation, is affected by the immigration and emigration of other members of the same species.

This exchange of individuals between neighboring populations contributes to an increase in genetic variation. An example of gene flow is found in chimpanzee communities living in natural reserves. When females reach reproductive age, they emigrate to a neighboring community where they are welcomed by the males.

The result is an exchange of alleles and changes in the gene pools of both communities.