While it is generally agreed that man entered the New World from Asia, the precise relationship between the American Indians and the Asiatic populations is obscure. A few of the difficulties involved in determining the origins and causes of American Indian racial differentiation are illustrated in this monograph.
Comas begins with a historical discussion in which the older views of American Indian racial unity are contrasted with the present conception of racial heterogeneity. He then deals with current theories that explain variability. The popular environmentalist theories that rely on Bergmann’s and Allen’s laws are rejected in favor of those that utilize genetic process. His consideration of genetics is confined largely to a discussion of the Diego factor, an antigen limited almost exclusively to American Indian and Mongoloid populations. A table showing the world distribution of the Diego factor is given. Finally, brief mention is made of the new finds of Homo sapiens in Asia.
Comas concludes that data discovered during the past decade have done little to clarify the problem of the origins of man in America.
