Racial Differentiation in Mankind

The existence of conspicuous diversity among human populations in physical appearance has been common knowledge at least since the time of ancient Egypt.  The subject is discussed at length in numerous books on physical anthropology and need not be considered here in detail.

There is no question that all mankind constitutes a single species in view of the absence of any physiological bar to hybridization between the most diverse races or of any recognizable loss of vigor in the first or later generations.

There is also no question, however, that populations that have long inhabited separated parts of the world should, in general, be considered to be of different subspecies by the usual criterion that most individuals of such populations can be allocated correctly by inspection.  It does not require a trained anthropologist to classify an array of Englishmen, West Africans, and Chinese with 100% accuracy by features, skin color, and type of hair in spite of so much variability within each of these groups that every individual can easily be distinguished from every other.

It is, however, customary to use the term race rather than subspecies for the major subdivisions of the human species as well as for minor ones.  The occurrence of a few conspicuous differences, probably due to selection for adaptation to widely different environmental conditions, does not necessarily imply much difference in general.  Nei and Roychoudhury (1974) have shown that the differences among negroids, caucasoids, and mongoloids in the protein and blood group loci are slight compared with those between individuals within any one of them. There is disagreement on the number of major races that should be recognized. At a minimum, the Australoids are added to the three referred to above.

- Sewall Wright, 1978.  Evolution and the Genetics of Populations, Vol. 4:  Variability Within and Among Natural Populations. Univ. Chicago Press, Chicago, Illinois. p 439.