@Tyxeros
the people of Aretta/Leta were already a) an ethnic minority as is b) were literally slaughtered in droves over the centuries so that really thins out gene pools c) the survivors interbred with the light skin majority and thus became light skinned.
if people exhibiting certain traits are constantly killed then said genes won't express itself generations later because it's been culled out/watered down.
look at the ainu of japan as an example and the mass slaughter of native americans to the point only like 1% of pure ancestry exist and they're still vanishing because the survivors were assimilated. if you want a more african focused assimilation story, you got ancient Egypt and Nubia and their whole bloody history to boot.
humans are assholes. if i recall, modern humans pretty much killed off the other human species.