Ancient genomes from Ladakh reveal 2800-year-old admixture between Tibetans and South Asians

Reconstructing population history is harder in South Asia than in many other world regions due to a paucity of ancient DNA. We report genome-wide data for 10 individuals from Old Lady Spider Cave, which lies 4000 meters above sea level in the Himalayan region of Ladakh and dates to around 1500 years before the present (B.P.). These individuals were genetically homogeneous and had an ancestry signature rare in South Asians today: admixed in roughly 50–50% proportions between a population well proxied by present-day North Indians and another genetically similar to ancient Tibetans. By analyzing the typical sizes of segments of DNA inherited from each of these ancestral populations, we find that admixture of these groups began at least 50 generations before the date of the individuals, that is, by around 2800 B.P.