So the real question is why did losing the dark skin coloration have an advantage for those that moved North? Was it because of Vitamin D and the lighter skin provided for more more production in an environment that required more clothing and had less sun or was it because the lighter skin had some other advantage such as sexual attractiveness?
Scientists said yesterday that they have discovered a tiny genetic mutation that largely explains the first appearance of white skin in humans tens of thousands of years ago, a finding that helps solve one of biology's most enduring mysteries and illuminates one of humanity's greatest sources of strife.
The work suggests that the skin-whitening mutation occurred by chance in a single individual after the first human exodus from Africa, when all people were brown-skinned. That person's offspring apparently thrived as humans moved northward into what is now Europe, helping to give rise to the lightest of the world's races.
Seems to me the Vitamin D angle would make more sense.
For you proponents of ID (Ignorant Design) this, of course, is a silly question since everyone knows that God is white.