"To me, it has really changed some of the story about the evolution of skin color," Sarah Tishkoff, a geneticist at the University of Pennsylvania and leader of the international team, told Axios. Some of the variations in pigmentation genes appear to have originated roughly 1 million years ago, well before the emergence of modern humans, she said.
The study: The team used a color meter to read the level of melanin in the inner-arm skin of more than 2,000 people from Ethiopia, Tanzania and Botswana and sequenced genes from almost 1,600 of them. Later, a team confirmed their findings by testing the variations in zebrafish and mouse models.
The team found several novel variations (called alleles) in genes associated with pigmentation:
- DDB1– repairs DNA damage done by ultraviolet light radiation and could be key to understanding melanoma.
- SLC24A5 and OCA2 – these genes are implicated in albinism
- HERC2 – regulates the OCA2 gene
- MFSD12 – Study author Nicholas Crawford told Axios "I remember I was very excited" when we found this gene is associated with vitiligo (an autoimmune disease that creates patches of light-colored skin on dark-skinned people). Tishkoff said their study found MFSD12 also contributes to the production of a protein that plays a role in optimizing nutrition and fighting infection. "This may be key to figuring out how to manipulate skin pigmentation for therapeutic means," she said.
Migration implications: The data collected is consistent with there being an early migration event of modern humans out of Africa along the southern coast of Asia and into Australo-Melanesia, Tishkoff said.
Africa is key: "Many variances rose in Africa and some [of those] went to 100% frequency in Europe so it was only by going to Africa and looking at these variables" that they discovered some of these new genes, said Tishkoff, who calls herself a "major advocate" to increase all studies of genetics in Africa.
- Rick Sturm, molecular geneticist at the University of Queensland who was not part of the study, agreed. "I had made a simple assumption that selection was happening on multiple genes in European populations as skin pigmentation was lightening, but I hadn't thought that similar process was happening in Africa for darkening."
- Sturm said there is more research to be done: "The identified [genetic variations] still only explain about 28.9% of the variance seen in pigmentation, so other genes remain to be discovered."
Go deeper: Listen to Tishkoff talk about the study on this Science podcast (9:55).
