Individual admixture proportions were estimated using a panel of 2,076 ancestry-informative SNPs assuming two clusters and uncorrelated allele frequencies with a 10,000 step burn-in and a 100,000 step chain using STRUCTURE (version 2.2) [Falush et al., 2003]. Ancestry-informative SNPs had the following characteristics 1) a minor allele frequency ≥ 0.01 in both the HapMap phase II CEU and YRI samples, 2) a difference in allele frequencies between the HapMap CEU and YRI samples ≥ 0.6, and 3) an r2 ≤ 0.4 with other SNPs within 1 Mb.
