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The Genetics Of The St. Thomas Christians, part 2

Last year I posted The Genetics of the St. Thomas Christians. Recently I got some more samples. Of these, four were clearly self-identified as Southist/Knanaya Christians (as opposed to Northist Christians). The Knanaya are a bit different in their traditions than the broader much larger St. Thomas Christian community.

In the PCA above the bottom left are Middle Eastern groups. Druze and Yemeni Jews. Toward the top are Lithuanians. Green are Iranians. From the bottom right, up a diagonal axis, you see south-north Indian cline from low caste Telugu Christians, to Jatts from Punjab.

It does seem in relation to the other more generically labeled St. Thomas Christians the four Knanaya show some noticeable Middle Eastern shift.

Here’s an admixture plot:

The St. Thomas Christians have more yellow “Druze” cluster than other South Indians, with variation (the Knanaya have more).

I ran some Treemix. Didn’t detect major gene flow, but the Knanaya group was different from the other St. Thomas Christians, having a closer position to West Eurasians. When I ran a three-population test, it was the St. Thomas Christians (Nasrani above), and not the Knanaya, which registered admixture with Middle Eastern groups. It’s probably an artifact that the latter was not detected.

The Christians of Kerala are very similar to other peoples of Kerala. But, I now think it is more than 50% likely that they do have detectable Near Eastern ancestry above what you should expect.


6 thoughts on “The Genetics Of The St. Thomas Christians, part 2

  1. Amali Williams, in 2004 article in “Antropologica” on whiteness and marriage in St. Thomas Christians, suggests that a trickle of marriage with lower-caste Christians was possible but kept in check by ritual significance of skin whiteness. Which was partly “hereditary but not genetic” (as in, hereditary privilege of carrying umbrellas) but primarily genetic. If so, shouldn’t one be able to identify signatures of selection at the pigmentation loci?

  2. Possibly a validation of some of the origin stories of St. Thomas christians. This does fall in line with some of Philip Jenkin’s book “Lost History of Christianity”:

    In the book it talks of how in the ancient past the Nestorian (Church of the East) was the biggest christian denomination and had spread across Asia including India. These christian traders settled in Kerala and establishing a community intergrating into the local culture as well as being part of the . Also I read in the past (forget the source), about a history of “west syrian” christian traders who using south india as a base, had networks all the way supposedly into south east asia, they were part of a business association in south india call the “Manigramman”. The Knanayas have maintained they are descendants of a later middle eastern settler migration and absorbing the local caste culture claimed they don’t intermarry with anyone else, maintaining pure blooded descendants (which they are not, some might be lighter than the average christian keralite, but they are very mixed, a good number of them just look like like the local populace). This is very fascinating thank you for sharing this Razib!

  3. Hello razib,

    can you run the same tests on the Cochin jews alongside the St. Thomas Christians (both Northist and Southist) ?

  4. Iranians have around 20% Telugu_ASI in the admixture plot, Those low caste Telugu christians could be 50% or more Western Eurasian?

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