Some people's most recent African ancestors lived there within the last few hundred years and others were many millenia ago. Of course then there are the Berbers that are a fair-skinned African tribe
In a double blind study, I believe people could do a pretty fair job of sorting say a hundred pictures of people who's families have lived in certain parts of the world for the last 20 or so generations, at least as to what continent they were from.
There is a scientific device to measure albedo: fresh snow measuring
For the record I don't consider myself racist, maybe it's not even a good thing that the brain can organize people by race, but I don't see any point in pretending it can't.
"A car is just a big purse on wheels." -- Johanna Reynolds