Many Nilo-Saharan-speaking populations in East Africa, such as the Maasai, show multiple cluster assignments from the Nilo-Saharan and Cushitic AACs, in accord with linguistic evidence of repeated Nilotic assimilation of Cushites over the past 3000 years and with the high frequency of a shared East African–specific mutation associated with lactose tolerance.
The modern Maasai display significant West-Eurasian admixture at roughly ~20%. This type of West-Eurasian ancestry reaches up to 40-50% among specific populations of the Horn of Africa, specifically among the Amhara people. Genetic data and archeologic evidence suggest that East African pastoralists received West Eurasian ancestry (~25%) through Afroasiatic-speaking groups from Northern Africa or the Arabian Peninsula, and later spread this ancestry component southwards into certain Khoisan groups roughly 2,000 years ago, resulting in ~5% West-Eurasian ancestry among Southern African hunter-gatherers.