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The · Psychohistorian


Long before Eve

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You have probably heard of "mitochondrial Eve". Mitochondria are the bacteria like organelles in most of our cells that provide our energy. "Mitochondrial Eve" is the last woman to have had mitochondria from which the mitochondria in all of us are descended.

In the late 1980s, research on mitochondrial DNA indicated that "mitochondrial Eve" had lived about 200,000 years ago. This was much more recent than the spread of Homo erectus across the old world about 2 million years ago, and spawned the "recent African replacement" theory that modern humans speciated at around the time of mitochondrial Eve, then went on take over the world by eliminating archaic human species like neanderthals and Homo erectus - without interbreeding with them, since different species don't interbreed. The theory became generally accepted, first in the popular press, then in most scientific circles.

Personally, I was dubious. We only get one copy of our mitochondrial DNA rather than two, meaning that drift would result in one strain taking over much faster than for autosomal DNA; for those reasons, the 200,000 year time didn't seem unexpectedly recent to me, so I found the theory questionable from the start. I also found the "no interbreeding" idea questionable.

At any rate, I held on to my minority opinion for a couple of decades. Last year, the neanderthal genome project finished, providing evidence that neanderthals did contribute to the modern gene pool. Perhaps more importantly, the discovery of a new archaic human form from southern Siberia was announced and it was also found to have contributed to the modern gene pool. Both of these lines left Africa long before "mitochondrial Eve" did.

I feel vindicated.

Discussion of neanderthal genome:
http://johnhawks.net/weblog/reviews/neandertals/neandertal_dna/neandertals-live-genome-sequencing-2010.html

Discussion of the denisova hominin, previously known as "X woman":
http://johnhawks.net/weblog/reviews/neandertals/neandertal_dna/denisova-nuclear-genome-reich-2010.html

It turns out there was a 2005 paper on the cumulative autosomal evidence to date at that time which rejected the recent African replacement hypothesis with p < 10**-17. I guess if I'd read that paper, I might have felt vindicated sooner:
http://esa.ipb.pt/pdf/28.pdf
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