I seem to recall that some years ago you posted an article about a DNA study of 10,000 year old British bodies that also had dark skin. In that case I remember thinking, OK, they could survive because they got Vitamin D from seafood. I suppose Otzi survived because he did not wear much cloting in the warmer seasons.
The hunter-gatherer diet in general was higher in Vitamin D than the diet of agriculturalists. It is theorized that farming populations in northern Europe quickly selected for lighter skin when their dietary Vitamin D declined.