Racial differences in pigmentation and natural selection

The inheritance of skin colour in man is not well understood. A clearer understanding could be obtained by taking into account the biological basis and genetical control of pigmentation in other mammals, particularly the experimental species. In these, most of the loci governing pigmentation are pleiotropic, colour being only one of the traits affected by them. Their products are evidently concerned with other metabolic pathways as well. There is strong evidence for inter-specific homology of pigmentation loci in mammals, and the situation in man may not be radically different. It is therefore possible that racial differences in skin colour may have resulted from the action of natural selection on these other functions of pigmentation genes.