The formation of human populations in South and Central Asia

By sequencing 523 ancient humans, we show that the primary source of ancestry in modern South Asians is a prehistoric genetic gradient between people related to early hunter-gatherers of Iran and southeast Asia. Following the Indus Valley Civilization’s decline, they mixed with people in the southeast to form one of the two main ancestral populations of South Asia whose direct descendants live in southern India. Simultaneously, they mixed with descendants of Steppe pastoralists who spread via Central Asia after 4000 years ago to form the other main ancestral population. The Steppe ancestry in South Asia has the same profile as that in Bronze Age Eastern Europe, tracking a movement of people that affected both regions and that likely spread the unique shared features shared between Indo-Iranian and Balto-Slavic languages