So here is the baseline: all humans share almost all of their DNA, a fact that betrays our recent origins from Africa. The genetic differences between us, small though they are, account for much, but not all, of the physical variation we see or can assess. The diaspora from Africa around 70,000 years ago and continual migration and mixing since, means that we can see that there is structure within the genomes that underlies our basic biology. Very broadly, that structure corresponds with land masses, but within those groups there is huge variation, and at the edges and within these groups,
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