Seriously, a primatologist friend was saying that for example, swahili women at the coast who cover themselves up totally with a ‘burkha’ are a modern day example and (if I remember the conversation correctly) the women will soon suffer from a vitamin D (or was is B?) deficiency and this will in many generations to come, affect the pelvis …. basically, survival of the fittest and they will have effectively taken themselves out of the ‘race’ . bigger brains and having to be born earlier and be helpless (not like other mammals where the young are born able to fend for themselves immediately) and eating fish so you adapt to move over the 45th parallel ….. but then swahili women live by the coast and eat fish so would that then, not protect them from rickets, even as they loose melanin… and I become more lost as I explain myself and this is what happens when an accountant speaks with a primatologist.

I have also heard that folic acid is light sensitive so southern peoples would derive a benefit from protecting it from the sun.

But arguing against the primacy of light is the claim that the melanin granules provide some anti bacterial and ant parasite properties which would be very useful in tropical regions like Africa.

It will be interesting to see how long-term immigration and modern travel alter racial compositions. If the advantages of specific skin colours to certain regions are strong enough they might keep being selected for and any lull in immigration would return each region towards its former skin tone even while unseen racial traits like blood antigens and such are altered completely in prevalence.