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Old 09-24-2012, 04:36 AM
foolsguinea foolsguinea is offline
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Because people often marry within their ethnic group, even to the point of preferring to marry first and second cousins in some tribal cultures, the MRCA model cited (being invented by relatively exogamous Yanks, I suspect) is useless.

The actual MRCA for all Homo sapiens is way, way back. For some isolated groups it could be thousands or myriads of years ago. Even excluding various isolated aboriginal groups and the whole Amerindian set, you have several genetically distinct groups in sub-Saharan Africa that may not have a particularly recent common ancestor with outsiders.

But for two people from the same ethnicity, like, say, two WASPs, yeah, more recently than 50 generations is reasonable.