Re: Setting: Reverse Concentration
That actually seems more in line with human migratory patterns.
The human population of Africa has the largest genetic diversity in the world. (I personally blame the Psilons).
But the middle east was a gateway from Africa into the rest of the world, then moving into Asia and Europe.
You should look up Human Migratory Patterns and genetic maps. I think wiki has some ok sources, but there is a ton of info out there.
To push toward the asian side of things, there is some interesting history regarding a Chinese fleet in the Song Dynasty,