That’s a big proportion! For comparison, a similar and much bigger study identified hundreds of genes that affect one’s height, but that collectively account for just 16 percent of the variation that you see in large populations. And they showed that these variants collectively account for 29 percent of the variation in skin color in the three countries studied. They found several, clustered around six specific genes: SLC24A5, MFSD12, DDB1, TMEM138, OCA2 and HERC2. Then the team looked at more than 4 million spots in the volunteers’ genomes where DNA can vary by a single letter, to identify which variations are associated with their skin color.
They recruited 1,570 volunteers from 10 ethnic groups in Ethiopia, Tanzania, and Botswana, and measured the amount of the dark pigment melanin in the skin of their inner arms. To redress that imbalance, Tishkoff and her team looked to Africa-the continent where humanity is at its most physically and genetically diverse. “It gives you a very incomplete perspective,” she says. To Sarah Tishkoff, a geneticist at the University of Pennsylvania, that’s a ridiculous state of affairs.
What we do know comes almost entirely from studying people of European descent. And yet, for all its social and scientific importance, we know very little about how our genes influence its pigment. Few human traits are more variable, more obvious, and more historically divisive than the color of our skin.
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