Africa had been breeding humans for a million years, so a big gene pool was established. <sub-Saharan Africans have greater genetic diversity than non-Africans, most likely because the non-African population declined to just a few thousand, at most.>
Then, a bunch of them spread out as per the map when conditions allowed. Of course, as with any migration, by salmon to a new stream, wolves to a new territory or people to a new island, it is a few leaving the mass. The few obviously have fewer genes in their pool.
They emigrants then rapidly breed, as things do, and fill the new niche with their descendants, who, of course, are from the same few genes.
Ipso facto, casus belli, ultra vires, infra vide, caveat emptor, inter alia it's obvious that humans outside Africa have a much smaller gene pool than those still in it, despite the numbers in the areas outside Africa. Yes, over the 30,000 years since the father of all we blokes left Africa, there would have been some more genetic drift and also some continued donations from Africa. But 30,000 years isn't a lot of time.
One could also predict that those at the ends of the chains who arrived most recently, such as at the tip of Chile, would have the least diverse gene pool. People in India, which has been the cross-roads of humans since 80,000 years ago would have a huge gene pool, though not quite as big as that of Africa.
With DNA tracking now available, lots of interesting detail on migrations will become available. And the timing of the travels.
Mqurice |
