There’s not too much that close readers of this weblog will find surprising. But it was interesting to see David explicitly assert that West Eurasian ancestral input into modern Indians was male mediated. This is clear if you compare the frequency of West Eurasian Y lineages (e.g., R1a1a) and the India specific M haplogroup. But I suspect that they’ve looked closely at X chromosomes, which spend 2/3 of their time in females, and these are probably enriched for Ancestral South Indian (ASI).
David emphasizes the admixture event that occurred on the order of ~3,000 years ago between Ancestral North Indians (ANI) and Ancestral South Indians (ASI) in the ethnogenesis of the genetic landscape of South Asia. But as I’ve stated here before I believe that the West Eurasian admixture pre-dates this. In particular, I believe that the Dravidian languages probably have a West Asian provenance. So here’s a revised model of what happened in South Asia. First, the West Asian intrusion resulted in a mixed population during the period of the Indus Valley civilization. But this was limited to the northwest corner of the subcontinent. It was with the arrival of the Indo-Aryan cultural toolkit that the rest of India, inhabited by predominantly ASI populations, was opened up to demographic expansion from the Northwest. Note that this does not mean that most of the ancestry was derived from the steppe.* Just that the intrusion for the steppe may have triggered a cultural shift which reshaped the landscape, rather like how the arrival of Huns on the Roman frontier triggered folk wanderings by German and Iranic (Sarmatian) peoples.
* I don’t know if David misspoke, but he stated that Ancient North Eurasians contributed a lot of ancestry to Indians.