Bengalis are like Tamils, and Jatts are sui generis, and Syrian Christians are not Brahmins

Zack Ajmal has closed comments on Harappa DNA. Though they were amusing, they had gotten out of control. But that doesn't mean that his blog still isn't a comment worthy. The data is still there. I check in on it every now and then, mostly because Zack's sample has populations which you can't find elsewhere. It can also answer some questions which I've always wondered about. So three things are now clear with his sample sizes/constituents

1) Like Tamils, Bengalis exhibit a dichotomous distinction between Brahmins and non-Brahmins genetically. By and large Bengali Brahmins seem only moderately effected by the distinctive East Asian admixture found in other Bengalis, and are rather like North Indian Brahmins. The other Bengali samples are very similar in having elevated East Asian admixture, and lower fractions of "Northwest" Indian affinities than the Brahmins. This is in contrast to the situation in Uttar Pradesh where there are non-Brahmin high castes who have similar genetic profiles to the Brahmins (e.g., Kshatriya).

2) The Jatt samples are unique and distinctive, and have more European-affinities than almost any other South Asian samples Zack has (more than Punjabi Brahmins, for example). And, they are relatively uniform in this pattern. To me this does suggest that these populations have a more recent infusion of ancestry from outside South Asia.

3) Syrian Christians have told me for years that their ancestors were Brahmins. Not necessarily all Syrian Christians, but their ancestors. This was so common I assumed it was false because there are about ten times more Syrian Christians in Kerala than Brahmins. The Harappa DNA results show that Syrian Christians are probably not descended from Brahmins, probably none in Zack's sample. But their genetic profile often matches that of the Nairs, and also other various castes. Unlike Bengali Brahmins, or Jatts, this implies to me that multiple communities have moved into the Syrian Christian category over the centuries.