The Ancient Origins of Both Light and Dark Skin

For a long time, both scientists and the general public assumed that skin color evolved to adapt to local conditions. While that idea hasn't been completely debunked, genetic research tells us skin color is a lot more complicated. Until recently just about all genetic research on skin color came from studies done on people of European descent. A new study, led by geneticist Sarah Tishkoff at the University of Pennsylvania, studied the genomes of over a thousand volunteers from ten ethnic groups in Africa, the most genetically diverse continent. The results upend the traditional idea that dark skin evolved to protect a person from the sun near the equator, while light skin evolved further north to let in scarce sunlight for vitamin D production.

But most of the variants that Tishkoff’s team identified, for both light and dark skin, have an ancient African origin. They likely arose in hominids like Homo erectus long before the dawn of our own species, and have coexisted in balance for hundreds and thousands of years. In many cases, the older variant is responsible for lighter skin, not darker. That’s consistent with an idea from Nina Jablonski, an anthropologist from Pennsylvania State University, who thinks that the ancient ancestors of humans—much like other primates—had pale skin. “As our ancestors moved out of the forest and into the savannah, they lost their hair and evolved darker skin,” says Nick Crawford, a researcher in Tishkoff’s lab.

The study doesn't pretend to answer all questions about skin color, but it opens some doors for further research. Read more details about the genetic study at The Atlantic.