One of the greatest faults and impediments of anthropology has always been and is largely to this day, in spite of ever-growing evidence to the contrary, the notion of the permanence of skull types, and their changeability only through racial mixtures and replacements. It is time that this attitude be replaced by more modern and rational views on the subject, based on the steadily increasing knowledge of biological laws and processes, together with such powerful factors as segregation and isolation.

… the isolation and small number of individuals in each community gave rise to long-continued inbreeding, and with it, to a sharp individualization of local types. This was emphasized by subtle influences of natural and social environment. With the slow increase in numbers, these types came into contact; and through mixture and migration a new distribution of typical forms developed.