Village and tribal genetic distances among American Indians, and the possible implications for human evolution.

Pair-wise genetic distances based on six genetic systems (Rh, MNSs, Kidd, Duffy, Diego, and haptoglobins) are presented for seven villages of Makiritare Indians, seven villages of Yanomama Indians, and 12 Indian tribes of Central and South America. It is shown that the mean genetic distance between Indian villages is 85-90 per cent of the distance between tribes. Since in the past, the initial event in the formation of a new tribe was probably the breaking away of one or several related villages from an established tribe, it is clear that this initial event could have profound consequences for subsequent tribal gene frequencies. By the criterion of changes in gene frequency in polymorphic genetic systems, the maximal rate of evolution in the American Indian has been approximately 100 times more rapid than the mean rate suggested by calculations based on amino acid substitutions in certain polypeptides of a variety of organisms. The above-mentioned findings could account in part for this 100-fold difference. Some other factors which might diminish the apparent difference between the results of these two types of calculations are mentioned.