Gene frequencies and microdifferentiation among the Makiritare Indians. IV. A comparison of a genetic network with ethnohistory and migration matrices; a new index of genetic isolation

Abstract

Genetic distances between seven Makiritare villages based on (a) six loci (Rh, MNSs, Kidd, Duffy, Diego, and haptoglobin), (b) five different loci (P, Lewis secretor, Gc, erythrocyte acid phosphatase, and PGM1), and (c) all 11 of these loci are presented. The village histories are then detailed, and a migration matrix of the Bodmer and Cavalli-Sforza (1968) type derived. It is shown that the actual behavior of these villages contravenes the assumptions necessary to the use of these matrices as visualized by Bodmer and Cavalli-Sforza. A genetic network (phylogeny) connecting the villages is derived by the technique of Edwards and Cavalli-Sforza (1964). The network based on the six and on all 11 loci agrees well with the historical data, but the five-locus network fits less well. The distorting effect of a large amount of exchange between two villages on the phylogenetic interpretation of such networks is shown. However, this technique may be useful in deriving a first approximation to the relationships of small population units where histories are less adequate than in this case, the reliability of the result being proportional to the number of systems studied. Finally it is shown that treatments which equate genetic isolation to geographic distance functions break down in populations of this nature. A new, simple approach to quantitating the genetic significance of migration is suggested.