The ability of smaller sets of In4 markers (96, 64, 48 and 24) to discern population genetic structure was also examined. Here, the smaller sets were in each case the highest ranking In4 SNPs (Supplementary Table S1 and see Supplementary Table S2 for additional summary information). The individual estimation of continental ancestry was nearly identical when 128, 96 or 64 In4 markers were used (e.g. compare Fig. 1c with 1a). A summary of all the results shows that as few as 24 In4, could in fact identify the same general population clusters (Table 2). Specifically, for both West African and European ancestry the results are very consistent with similar proportion of population measurements seen even when comparing 128 In4 with 24 In4 results. For the Amerindian and East Asian continental population groups there is a modest fall-off in the concordance with self-identification as the numbers of markers decrease, for example, the cluster membership that corresponds best to self identified Amerindian ancestry (pop 4) decreased from 0.94 (128 In4) to 0.88 (24 In4) (Table 2). However, the difference is more pronounced
