The top two PCs of AA and EA samples and with the Phase II Hapmap CEU and YRI samples are shown in Supplementary Figure 1. Outliers were defined as subjects whose ancestry was at least 3 standard deviations from the mean of the two largest PCs. This step removed 33 AAs and 127 EAs, retaining 1264 AAs and 2613 EAs in the final cleaned dataset.
