Okay, just speculation based on the 70Kya date for 'out of Africa' & a 20,000 year time period needed for skin color shift. I'm sure I recall the 20K figure, and I think I heard of that on the PBS Nova program on the Vit.D/folate theory.
I also allowed 20K years for migration first, but this selection is always happening. I imagine that at some point ~60-30Kya populations became stable enough in one region that color shift took place. I probably should have said 40-30Kya +/-20K years.
Neat info. about the keratin and eyes too.
Thanks,
~samwik

Pyrolysis creates reduced carbon! ...Time for the next step in our evolutionary symbiosis with fire.