Teju Cole begins his collection of essays Known and Strange Things with a composition on the “Black Body”. James Baldwin had written about his visit to a Swedish village called Leuk and Teju Cole, in his quest for what identity means in the postmodern world, had visited the same place to merge and un-merge the memories Baldwin had when he was the only black person in Leuk. When Baldwin visited the place his lover lived, no black person had ever visited it before. It was a strange event in the village and a big spectacle for the white boys. Till today, our skin means many things: a defining characteristic of race, and a starting point for racism.
“If you ask somebody on the street, ‘What are the main differences between races?’ They’re going to say skin color,” said Sarah A. Tishkoff, a geneticist at the University of Pennsylvania.
On Thursday, Dr. Tishkoff and her colleagues showed this to be a profound error. In the journal, Science, the researchers published the first large-scale study of the genetics of skin color in Africans.
The researchers pinpointed eight genetic variants in four narrow regions of the human genome that strongly influence pigmentation — some making skin darker, and others making it lighter.
These genes are shared across the globe, it turns out; one of them, for example, lightens skin in both Europeans and hunter-gatherers in Botswana. The gene variants were present in humanity’s distant ancestors, even before our species evolved in Africa 300,000 years ago. The widespread distribution of these genes and their persistence over millenniums show that the old color lines are essentially meaningless, the scientists said. The research “dispels a biological concept of race,” Dr. Tishkoff said.
Humans develop color much as other mammals do. Special cells in the skin contain pouches, called melanosomes, packed with pigment molecules. The more the pigment molecules, the darker the skin.
Skin color also varies with the kind of pigments: Melanosomes may contain mixtures of a brown-black called eumelanin and a yellow-red called pheomelanin.
To find the genes that help produce pigments, scientists began by studying people of European ancestry and found that mutations to a gene called SLC24A5 caused cells to make less pigment, leading to paler skin. Unsurprisingly, almost all Europeans have this variant.
“We knew quite a lot about why people have pale skin if they had European ancestry,” said Nicholas G. Crawford, a postdoctoral researcher at the University of Pennsylvania and a co-author of the new study. “But there was very little known about why people have dark skin.”
Since the early 2000s, Dr. Tishkoff has studied genes in Africa, discovering variants important to everything – from resistance to malaria to height. African populations vary tremendously in skin color, and Dr. Tishkoff reasoned that powerful genetic variants must be responsible.
Studying 1,570 people in Ethiopia, Tanzania and Botswana, she and her colleagues discovered a set of genetic variants that account for 29 percent of the variation in skin color. (The remaining variation seems tied to genes yet to be discovered.) This new study provides a deeper appreciation of the genetic palette that has been mixed and matched through evolution.