Reconstruction of the genetic history of the Austro-Asiatic- and Dravidian-speaking tribal populations of South Asia.

The ancestors of Austro-Asiatic- and Dravidian-speaking tribal populations are among the earliest settlers of South and Southeast Asia (S&SEA). While Austro-Asiatic speakers are distributed across S&SEA, Dravidian speakers are primarily confined to South India. Previous studies have identified the Indian Austro-Asiatic and Dravidian tribal populations to maximally represent two distinct genetic ancestral components, ancestral Austro-Asiatic (AAA) and ancestral South Indian (ASI), respectively. Leveraging the whole genome sequence (WGS) dataset from GenomeAsia 100K project, we investigated the genetic relationship of the tribal populations within the broader South Asian demographic landscape. Our analyses reveal that AAA and ASI components diverged ∼15,000-20,000 years before present (ybp), shortly after Last Glacial Maximum-a period marked by ecological shifts and regional isolation. This divergence postdates the separation (∼20,000-30,000 ybp) between the Indian (AAA) and Southeast Asian (AAM) Austro-Asiatic ancestries, indicating a deep and widespread pre-Neolithic distribution of this ancestral population across S&SEA. Additionally, recent (∼750-1500 ybp) gene flow between Central Indian Dravidian and Austro-Asiatic tribes produced notable genetic-linguistic discordances.