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Scientists have identified the genes that lead to graying hair and unibrows

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Scientists have, for the first time, identified specific genes linked to graying hair, eyebrow and beard thickness, and unibrows, in a study of the genomes of more than 6,000 Latin Americans. The findings could help reconstruct what a person looks like from their DNA — useful in forensics and anthropology.

Each of the genes the team found was already known to play a role in related traits, the researchers wrote in the journal Nature Communications. For instance, the gene IRF4, which was associated with graying hair, is also involved in the production of melanin, the pigment that determines hair, skin, and eye color.

The study's population made the comparisons possible. The volunteers had highly mixed ancestry; this particular group was a mix of European (48 percent), Native American (46 percent), and African (6 percent) descent. Most past studies on hair genetics have taken place in Europe, which only represents a small portion of human diversity. And even then, those studies were mostly focused on the frequency of the traits, says Andrés Ruiz-Linares, a biosciences professor at University College London and a co-author of the paper.

Previous studies were too focused on Europeans

The participants' mixed ancestry in today's study provided the researchers with healthy variations in hair types. That's part of what allowed the group to identify multiple genes that affect hair type and growth, according to Ruiz-Linares. "We then concentrated on features in particular that have been reported to differ between Native Americans and Europeans just to try to exploit the mixed ancestry of the population," Ruiz-Linares says.

Ruiz-Linares points to IRF4 and its association with graying hair as an example. About 15 percent of Europeans carry it, but it hasn't been found in Native Americans. The genes could perhaps be used to change a hair's color while it's forming in the follicle — not just after it's grown. The cosmetic industry will find this of interest, Ruiz-Linares says, specifically the genes linked to hair graying and hair type. "Identifying these genes puts forward targets that the industry might want to exploit," he says.

The presence of these genes doesn’t guarantee a specific trait. But it makes it a lot more likely. "It’s not like you have that [gene] variant, so you’re certain to have gray hair," Ruiz-Linares says. "No. It basically increases your chances relative to the general population."

The findings could also influence disciplines from criminal forensics to anthropology — by suggesting how to reconstruct physical appearance from DNA. This is especially the case with genes like Foxl2 and PAX3, which the study found to be associated with eyebrow and unibrow thickness, but were already known to affect structural development of those areas. "There’s always an interest in trying to predict what these people that lived a very long time ago looked like," Ruiz-Linares says. This new data can help refine those predictions and profiles.

Correction: This article originally stated that the paper was published in Nature. It was published in Nature Communications. The article has been updated to reflect this change.