The low correlation between estimates for European contribution in PRA may be explained by the fact that three ancestral populations, Europeans, Amerindians, and West Africans, have substantial contributions in the PRA population. This is unlike AFA and MAM/MXN, where there are two main contributing ancestral populations, West African and Europeans, and Amerindian and Europeans. Using r2 >0.8 as a threshold for high correlation, any of the In4 sets should be acceptable to estimate West African contribution in AFA, 128 In4, 96 In4 and 64 In4 are sufficient for Amerindian contribution in Mexican and Mexican American populations, and 128 In4 and 96 In4 sets should provide sufficiently accurate information for European contribution in PRA.
