For each population, heterozygosity was computed for each locus using the unbiased estimator of Weir (1996)[46], and the average across loci was taken as the population estimate. Calculation of F ST was performed using eq. 5.3 of Weir (1996)[46]. The expected heterozygosity (I) for the Mestizo was calculated using the expression of Rosenberg and Huang (personal communication): Where IA and IB are the observed heterozygosities of European and Native American populations, F the F ST estimated between Europeans and Africans, and γ the proportion of European ancestry in the Mestizo. A related expression for the expected heterozygosity after admixture of three populations (i.e. including Africa) did not produce a significantly better fit with the data analysed here.
