UNIVERSITY PARK, Pa., June 21 (UPI) — Pale people who never tan and those who bronze deeply can thank their ancestors, two U.S. anthropologists suggest.
Nina Jablonski and George Chaplin of Pennsylvania State University looked at the way the sun illuminates different parts of Earth at various latitudes.
They note ultraviolet radiation, which can produce vitamin D in human skin, can also destroy folate — a nutrient needed for good neural tube growth during pregnancy. The researchers previously concluded dark skin pigmentation in the tropics protects people from folate destruction by ultraviolet B.
“What we now recognize is that some of the medical problems seen in darkly pigmented people may be linked at some level to vitamin D deficiency,” Jablonski says in a statement. “Things like certain types of cancer in darkly pigmented people and in people who use a lot of sunscreen or always stay inside could be partly related to vitamin D deficiency.”
The researchers note that the ability to tan developed in a wide variety of people and while the outcome, tanablity, is the same, the underlying genetic mechanisms are not necessarily identical.
The report, published in the Proceedings of the National Academy of Science, says arguments about the selective value of dark pigmentation focused on the protective effects of melanin against sunburn, skin cancer and overproduction of vitamin D. These factors can no longer be considered significant selective pressures.
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