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Founder effects

Source: TW

Indian populations with a larger founder effect than Ashkenazi Jews. Many Indian populations descend from severe founder effects, consequence of which is compounded due to caste endogamy.

Listed below are IBD (Identity by Descent) scores that exclude recent cousin marriage. Image On the rightmost are Ashkenazi Jews (IBD = 0.9), highlighted in gold. On the leftmost are Onges, an isolated tribal group with IBD score = 30 (the chart is scaled so it doesn’t show 30).

A large number of South Indian scheduled caste groups seem to have terrible founder effects. There are also huge founder effects in Gujjars, Baniyas and Jains. The Kalash tribe also has a bad founder effect. These effects lead to genetic abnormalities and increased risk of recessive diseases without any consanguinity. Contrary to popular beliefs, most upper caste Indians barely suffer from a large founder effect (notable exceptions are UP Baniyas and Jains).

In fact, many pops have lower founder effects than European Americans (which is a very good standard to pass)

CEU = European American Image

This essentially means that amongst upper caste Indians, the caste system has had little negative effects in terms of compounded risk for recessive diseases or other things that usually come as a product of consanguinity. Also, not just UC Indians but also a lot of OBC and SCs do not have any founder effect. The biggest problem seems to be amongst SI tribes/SCs who were cut off from the Indian genepool apparently due to caste based endogamy not favoring them & people avoiding mixing with them.