He extended this work to populations , calculating the degree of inbreeding of members of populations as a result of random genetic drift . Together with Fisher , he pioneered methods for calculating the distribution of gene frequencies among populations as a result of the interaction of natural selection , mutation , migration and genetic drift . He extended this work to populations , computing the amount of inbreeding of members of populations as a result of random genetic drift , and he and Fisher pioneered methods for computing the distribution of gene frequencies among populations as a result of the interaction of natural selection , mutation , migration and genetic drift .