Question for you and @hbdchick: obviously the decreasing diversity of more distant populations makes sense, but shouldn't differences in inbreeding show up more here? Shouldn't offspring of cousin marriages be much more homozygous, so wouldn't you expect populations with more
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cousin marriage to show up higher on this graph even in populations with greater genetic diversity present in the population as a whole?
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Replying to @HbdNrx @JayMan471
it's tricky, 'cause other things can also make pops more homogeneous or not (in their dna) like bottlenecks. so pops in americas very...
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...similar genetically speaking, 'cause they went thru huge bottleneck of migrating to the new world.
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the different processes (say bottlenecks vs. cousin marriage) do leave different signatures in pop genomes, tho, in varying lengths in...
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...runs of homozygosity (roh). here you can see that new world pops share a lot of short roh (bottleneck) while middle easterners...pic.twitter.com/u39XDALglj
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...share a lot of medium length roh thanks to inbreeding. so, there's diff sorts of varation in homizygosity for diff reasons.
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Replying to @hbdchick @JayMan471
So, in this data overall it looks like the effects of human migration out of Africa are dominating any recent cousin marriage practices, but perhaps if we compare the 1-2Mb range to the 4-8Mb range there we can see how more recent practices are reducing the Euro and East Asian
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bars. That is, the Euro and East Asian bars drop much more than some other groups as we move up from the 1-2Mb range. We would expect the ratio of short to long ROH to decline with more recent inbreeding.
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Overall though, I suppose I'm a little surprised that the more recent differences in marriage practices appear to be pretty small compared to the initial dispersal.
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