Arctic natives have darker skin, but they live TOO far north for skin-synthesis of Vitamin D from sunlight to work, so light skin would have had no survival value to them. In the winter they get little or no sunlight, and all year they are covered up enough that they get minimal sun exposure. They get all the vitamins they need from fish and meat.
This also tends to disprove the vegan contention that vegetarianism is the most "natural" diet for humans. It's really hard for humans to get all the nutrients we need from just plants.
Harvard medical researchers claim that 92% of American black children and 80% of Hispanic are currently vitamin D deficient. This has little evolutionary effect, they reproduce pretty well. Vitamin D deficiency has some but not much evolutionary pressure. It is insufficient to explain the sudden appearance of white skin. Wouldn't lighter skin have been sufficient to produce vitamin D more efficiently? Pure white skin is cosmetic, and could not have been primarily driven by a minor issue like vitamin D deficiency. The vitamin D theory is neat, tidy, and politically correct, but insufficient in reality. It is not settled science by any means.