Jewish mtDNA

 

The Ashkenazi group shows a foundational effect, with very few (maybe four) Western European females founding the community. The Sepharadi communities also have foundational females. The small Belmonte and Caucasus communities all have one or two "mothers", but also the Iranian and Iraqi Jewries show four or five local women responsible for half of their population. Moroccan and other North African communities have no founder effects, and interestingly, they have no Sub-Saharan introgression that is common in the host populations. The Ethiopian group is 100% African, with no connection to other Jewish communities. 

How is it that after a few hundred years of foundation, most of the female mtDNA lines disappear, and only a few survive? Do the missing ones die off, assimilate, or never come into existence? Apparently, selection acts most strongly on the females. 

CLAUDE the AI says that the reduced number of female founders in isolated communities is because of genetic drift, by pure chance. After ten or so generations, the number of surviving lineages is reduced by half.