Not sure, but some combination... I think there's been significant gene flow among populations for a long time, but that most modern human genes are mostly recently out of Africa. But some of them may have first gone back into Africa from elsewhere... #complicated
Reminder: finding some mutations that _allowed_ brain expansion is very different from identifying the selection pressures (reproductive benefits) for growing a bigger brain, given the energetic costs.https://twitter.com/NicoleBarbaro/status/1032625744629964800 …
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It must've started with getting back at the giant meat-head that bullied Joe Neolithic back in the day.
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