Ancient genomes from Ladakh reveal 2800-year-old mixture 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 ten 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 present (BP). 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 mixture of these groups began at least fifty generation before the date of the individuals, that is, by around 2800 BP.