However, as our forebears began to migrate, wandering far from the equatorial sun, not enough UV could make its way through the protective melanin.
In tropical climates, enough UV penetrates even dark skin to provide an adequate dose of vitamin D. More recent studies show its value in immune function and for fighting off certain cancers and even heart disease. Vitamin D, as most of us learned in elementary school, is critical for strong bones and healthy teeth. Why and how did lightly pigmented skin come about? The answer, Jablonski reasoned, involves another key vitamin-and the history of human migration.Īs Jablonski explains, the sun’s ultraviolet rays, in addition to causing cell damage and other forms of harm, play a vital role in human health: They trigger the production of vitamin D in the skin. These and other observations gradually led her and her husband and collaborator George Chaplin, Senior Research Associate in Penn State’s Department of Anthropology, toward a new hypothesis: that humans evolved the ability to produce melanin, the dark-brown pigment that acts as a natural sunscreen, as a way of safeguarding the body’s store of folate.Īt the outset, then, living near the equator, all humans would have had dark skin. In men, she learned, folate is vital for sperm production. Other research tied folate deficiency in pregnant women to various birth defects. In a 1978 paper by two American medical researchers, Jablonski found evidence linking exposure to strong sunlight with low levels of folate, an essential B vitamin, in the blood. Blocking their occurrence would offer little or no evolutionary advantage.
But skin cancers, Jablonski knew, almost always arise later in life, when an individual is past reproductive age. Theory held that darker skin had evolved in order to afford early humans-who had recently lost the cover of fur-a protection against skin cancer under the tropical sun. In the early 1990s, the evolution of skin color was regarded by many of her peers as an intractable problem. Shifting that focus not only resulted in fascinating discoveries about what makes us the color that we are, but a body of work highlighted by dozens of papers, two books, public education programming on the origin of skin color, television and radio appearances on NPR, PBS, late night talk shows, and a TED talk that has garnered more than a million views. Up until that point, Jablonski was known for her work in primatology and research on Old World monkeys. It all began in the early 1990s when Jablonski began exploring gaps in the literature about the evolution of human skin and skin color. These are a few questions that form the basis for what Penn State anthropologist Nina Jablonski calls an explanatory framework of the evolution of skin pigmentation in modern human beings. But what is it that brought about such a diversity of human skin colors? And how can knowledge about the natural history of skin inform questions surrounding societal notions of skin color and our health?
We inherit our skin color from our ancestors, and so it is obviously a trait that is tied to our biology and genetics.