Genes behind evolution of human skin colour identified

Researchers have found that mutations associated with both light and dark pigmentation in diverse African populations that originated more than 300,000 years ago, and some emerged roughly one million years ago, well before the emergence of modern humans.

New York: Scientists have identified new genetic variants that sheds light on genetics of skin colour, human evolution as well as explains the risk factors for skin cancer.

Researchers from the University of Pennsylvania found mutations associated with both light and dark pigmentation in diverse African populations that originated more than 300,000 years ago, and some emerged roughly one million years ago, well before the emergence of modern humans. 

"We have identified new genetic variants that contribute to the genetic basis of one of the most strikingly variable traits in modern humans," said Sarah Tishkoff, Professor at the varsity. 

"When people think of skin colour in Africa most would think of darker skin, but we show that within Africa there is a huge amount of variation, ranging from skin as light as some Asians to the darkest skin on a global level and everything in between," Tishkoff added.

The findings, published in the journal Science, could also help to explain why some people are more prone to skin cancer, and could even be used to develop new treatments for the disease.

Both light and dark skin pigmentations confer benefits: Darker skin, for example, is believed to help prevent some of the negative impacts of ultraviolet light exposure, while lighter skin is better able to promote synthesis of vitamin D in regions with low ultraviolet light exposure, the researchers said.

"Skin colour is a classic variable trait in humans, and it's thought to be adaptive," Tishkoff said. 

"Analysis of the genetic basis of variation in skin colour sheds light on how adaptive traits evolve, including those that play a role in disease risk," Tishkoff noted.

For the study, the team used a colour meter to measure the light reflectance of the skin of more than 2,000 Africans people in Ethiopia, Tanzania, and Botswana. 

They then genotyped 1,570 of those individuals for more than four million single nucleotide polymorphisms (SNPs) across the genome.

The researchers found four key areas of the genome where genetic variation closely correlated with skin colour differences.

Within these regions, the researchers focussed on six genes linked to pigmentation: SLC24A5, MFSD12, DDB1, TMEM138, OCA2, and HERC2.