Recently a Bohra Patel emailed me to express some exasperation that people are quoting me saying that the ancestry of South Asian Muslims is almost all from Hindus (or non-Muslims). Basically, I say things like this “99% of the ancestry of South Asian Muslims is indigenous.” This means some people are going to be 75% indigenous, but the majority probably have no West Asian segments of DNA. This does not mean they don’t have a genealogical line of descent. I myself am ~100% South Asian if you look at my genes…but my maternal grandmother’s father was from a lineage that had migrated to Bengal in the 19th century from Delhi. Before they were in Delhi they had left Persia in the 17th century with the forced conversion of the whole religious class to Shia Islam. This is validated through a Koran with all direct male line descendants listened. I am not one of those descendants (my maternal grandmother is not “in the book”), but I’m pretty sure my distant cousins who are paternal descendants no longer have any detectable Iranian ancestry either. Why?
The reason is that eight generations back there is only a 50% chance that you will any segment of identifiable DNA from an ancestor. Another way to say this is that 200 years ago you had many ancestors, but there’s only a 1 out of 2 probability that you will have identifiable DNA passed down through the generations from that person. Since my Iranian lineage (a man who left Iran, settled in South Asia, and married into the South Asian Muslim community) dates back 350 years, it’s totally unsurprising that there’s no evidence that isn’t documentary at this point.
In any case, I’m looking more closely at the assertion I made above. I ran a supervised analysis on some samples. You can see the results below. I’ll probably do f-stats too…but that takes a while to run. I may ‘update’ my estimate from 1% to closer to 5%, though I’m not convinced. The Bohra Patel is in the sample, it’s clear they are enriched for “Yemenite Jewish” ancestry. But, even with 200,000 markers, there are Hindu individuals that are 1-2% (Tamil Brahmin) because of the way the model is set up.
Really what’s needed are huge Y chromosome panels. Since that’s an unbroken lineage, and the gene flow is mostly through men from everything we know.
But the real problem is Iranian ancestry because there is something of a “cline” in the northwest of the subcontinent. How exactly are we supposed to detect Iranian ancestry in Punjabis that is recent? Ultimately it’s going to have to be IBD segments in large panels.
That being said, there is an indirect way to detect Muslim West Asian ancestry: look for Turkic and African segments. These come from Muslims, and so can serve as a tracer that is much more distinct from the Indian genetic landscape.
Finally, the flip side of these comments about the minimal impact of West Asians on the genes of South Asian Muslims is that it should make us more skeptical of the arguments of some Hindu nationalists and Muslim fundamentalists about how brutal the Turks were. I’m sure they were brutal…but they didn’t leave much of a genetic impact on Muslims, let alone Hindus. Most people were likely pretty insulated from the predations, probably because cities were demographic sinks anyhow.