“There is one notable exception to Jablonski and Chaplin’s equation—and it’s the exception that proves the rule. The Inuit—the indigenous people of the subarctic—are dark-skinned, despite the limited sunlight of their home. If you think something fishy’s going on here, you’re right. But the reason they don’t need to evolve the lighter skin necessary to ensure sufficient vitamin D production is refreshingly simple. Their diet is full of fatty fish—which just happens to be one of the only foods in nature that is chock-full of vitamin D. They eat vitamin D for breakfast, lunch, and dinner, so they don’t need to make it. If you ever had a grandmother from the Old World try to force cod liver oil down your throat, she was onto something for the same reason—since it’s full of vitamin D, cod liver oil was one of the best ways to prevent rickets, especially before milk was routinely fortified with it.   IF YOU’RE WONDERING how people who have dark skin make enough vitamin D despite the fact that their skin blocks all those ultraviolet rays, you’re asking the right questions. Remember, ultraviolet rays that penetrate the skin destroy folate—and ultraviolet rays that penetrate the skin are necessary to create vitamin D. Dark skin evolved to protect folate, but it didn’t evolve”