I wonder how Hitler would have responded to the following. Dark skin is well adapted to tropical, unforested regions where ultraviolet radiation is particularly intense. Lighter skin makes a person more susceptible to skin cancers from this kind of radiation, making them less likely to survive and outcompete darker skinned humans in these regions. Lighter skin is less of a problem in the North where there is less intense ultraviolet radiation, or in forested regions where humans can live most of the time in the shade of the trees, but darker skinned peoples can live in the North with just as much ease so Caucasians gain no competitive advantage due to skin color in the North. As it turns out, Caucasians are lighter skinned because their bodies produce a defective form of a skin protein Mc1r (melanocortin-1 receptor) which is necessary for the production of melanin. In other words, being Caucasian is actually a bodily disfunction! Some Caucasians from Northwest Europe have completely lost the ability to tan, and instead burn and peel after sufficient exposure to the sun - clearly not a superior condition to NOT burning and peeling, and as it turns out - quite dangerous.

http://anthro.palomar.edu/adapt/adapt_4.htm