ScienceDaily (May 3, 2012) The common occurrence of blond hair among the dark-skinned indigenous people of the Solomon Islands is due to a homegrown genetic variant distinct from the gene that leads to blond hair in Europeans, according to a new study from the Stanford University School of Medicine.

“This is one of the most beautiful examples to date of the mapping of a simple genetic trait in humans,” said David Reich, PhD, a professor of genetics at Harvard University, who was not involved in the study.

The study identifying the gene responsible for blond hair in the Solomon Islands, a nation in the South Pacific, represents a rare case of simple genetics determining human appearance, and shows the importance of including understudied populations in gene mapping studies, said co-senior author Carlos D. Bustamante, PhD, professor of genetics at Stanford. The findings were published May 4 in Science.

“Since most studies in human genetics only include participants of European descent, we may be getting a very biased view of which genes and mutations influence the traits we investigate. Here, we sought to test whether one of the most striking human traits, blond hair, had the same — or different — genetic underpinning in different human populations,” Bustamante said.

Globally, blond hair is rare, occurring with substantial frequency only in northern Europe and in Oceania, which includes the Solomon Islands and its neighbors. “Its frequency is between 5 and 10 percent across the Solomon Islands, which is about the same as where I’m from,” said co-first author Eimear Kenny, PhD, who was born in Ireland.

Many assumed the blond hair of Melanesia was the result of gene flow — a trait passed on by European explorers, traders and others who visited in the preceding centuries. The islanders themselves give several possible explanations for its presence, said co-senior author Sean Myles, PhD, a former Stanford postdoctoral scholar who is now an assistant professor at the Nova Scotia Agricultural College. They generally chalked it up to sun exposure, or a diet rich in fish, he said.

After researchers at UCSF generated genetic data from the samples, Kenny, a postdoctoral scholar in Bustamante’s lab, began the analysis in September 2010, the week she started at Stanford. “Within a week we had our initial result. It was such a striking signal pointing to a single gene — a result you could hang your hat on. That rarely happens in science,” she said. “It was one of the best experiences of my career.”

In terms of genetic studies, the analysis was straightforward, said Kenny. But gathering the data, accomplished in 2009 by Myles and co-first author Nicholas Timpson, PhD, was more difficult. Much of the Solomon Islands is undeveloped, without roads, electricity or telephones. It’s also one of the most linguistically diverse nations in the world, with dozens of languages spoken.

It was a return trip for Myles who had been there in 2004 as a graduate student with Max Planck Institute molecular anthropologist Mark Stoneking, PhD, (also a co-author of the study) to investigate whether the language variations correlated with genetic variations. While there, Myles was fascinated by the ubiquity of blond hair, which was especially common among children.

“They have this very dark skin and bright blond hair. It was mind-blowing,” said Myles. “As a geneticist on the beach watching the kids playing, you count up the frequency of kids with blond hair, and say, ‘Wow, it’s 5 to 10 percent.’”

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