I wonder how long it took the Africans who migrated North, to lose their melanin and look white...
Actually the Eurasian population migrated out of Africa 40k years ago.
They were dark skinned like today’s Australian Aborigines.
But then agriculture was discovered. Now agriculture gave a lot of food but not enough vitamin D that we need. It didn’t matter in Iraq, but as those populations migrated to the less sunny regions and reduced the meat in their diets, the darker skinned ones weakened and died.
The lack of melanine to become pale skinned happened in only a few dozen generations or less. You can see this in Sardinians who are among the most ancient Europeans and have mostly neolithic Iranian farmer ancestry.
And among Inuit who are quite a lot swarthier than Swedes as Inuit are nearly pure meat eaters who love them livers filled with vitamin D