Let's take a look at the Bengali participants of the Harappa Ancestry Project.
I have added a suffix to the IDs where B = Brahmin, V = Vaidya and M = Muslim.
Here are the HarappaWorld Admixture results for the Bengalis which you can also see in a spreadsheet.
It's easy to see the difference between the Brahmins and others.
Razib wanted to know the origin of the East Asian ancestry among the Bengalis. So I ran a supervised ADMIXTURE with the following populations set as ancestral:
While most of these populations are various East Asian groups, I used the Gujarati-A as the South Asian group since it has the most South Indian + Baloch components without any East Asian influence. I used the Georgians as a proxy for West Asian ancestry.
Since it's K=36, I ran ADMIXTURE 10 times with different seeds and computed the average percentages for the Bengali participants. The number of SNPs was about 85,565. I did a similar analysis at K=35 after excluding the Tibetans, which got me 263,000 SNPs. The results were broadly similar.
I am showing only the first 12 ancestral components since all the rest were less than 0.5% for all the Bengalis (Spreadsheet).
Please do remember that in supervised ADMIXTURE, I assign the ancestral populations and the algorithm has to find the best fit using those populations. So it's not showing actual ancestry but broad affinity. Also, the exact percentages are not important and can vary when I change the parameters of the analysis. Just look at the broad trends.
The general pattern is that Bengali Brahmins have the least Eastern Eurasian and the most West Asian. The Eastern Eurasian ethnicity most closely related to Bengalis is Burmese.
Interestingly, there is a pattern of a small amount of Siberian ancestry among these Bengalis. Let's add all the Siberian and Russian Far East groups.
||West Bengal Rajput
I am not sure of the pattern here, but at least the first few are above noise thresholds.