Science reports:

South Asia is home to one of the most diverse assemblages of people in the world. A mélange of different ethnic identities, languages, religions, castes, and customs makes up the 1.5 billion humans who live here. Now, scientists have revealed the most detailed look yet of how this population took shape.

In the largest ever modern whole-genome analysis from South Asia—published as a preprint last month on bioRxiv—researchers reveal new details about the origin of India’s Iranian ancestry and when ancient hunter-gatherers settled the region. The study also turns up a surprise: an unexpectedly rich diversity of genes from Neanderthals and their close evolutionary cousins, the Denisovans. Because no fossils of these ancient human relatives have been found in India, researchers are speculating about how these genes got there—and why they stuck around.

Global genetic sequencing efforts have largely ignored India, says population geneticist Kelsey Witt of Clemson University, who wasn’t involved with the work. So, “We’re learning a lot about populations that we didn’t know much about.”

Most Indians are primarily a mixture of three ancestral populations: hunter-gatherers who lived on the land for tens of thousands of years, farmers with Iranian ancestry who arrived sometime between 4700 and 3000 B.C.E., and herders from the central Eurasian steppe region who swept into the region sometime after 3000 B.C.E., perhaps between 1900 and 1500 B.C.E. [Continue reading…]