A population is defined through its gene pool. All populations from which individuals can mate and reproduce form a species. The species Homo sapients sapiens consists of a number of populations: Geography and custom may make it unlikely that a member of the Inuit (Eskimo) population will mate with a member of the Melanesian population, but it is biologically possible; the distinctly different gene pools of Inuit and Melanesians do not pose an impediment.