It is known that skin and hair color is mostly inherited from parents but whole populations have evolved to share certain traits. It is also known that people who live closer to the equator have darker skin and hair colour to protect against the Sun. The exception is found in the Solomon Islands, an archipelago east of Papua New Guinea which has the highest proportion of natural blonds outside of Europe despite being just south of the equator.
It was noted that although the indigenous Melanesian population possess the darkest skin outside of Africa, between five and ten per cent also have bright blond hair. Researchers from Bristol University have identified the single genetic mutation that causes the islanders to have such contrasting pigmentation of their skin and hair. In a study published in the Science journal, scientists took DNA samples from islanders and identified the variation which caused a difference in the cells responsible for dark pigmentation.
They add that since the gene - called TYRP1 that natives of the Solomon Islands possess, is not found in Europeans, the genetic trait could not have been introduced by western explorers. They suggest the characteristic arose independently in the region.
“So the human characteristic of blond hair arose independently in equatorial Oceania. That's quite unexpected and fascinating,” said lead author Eimear Kenny, a postdoctoral scholar at Stanford University in California.
Researchers gained the trust of a local chief and collected data from 1000 people, including hair and skin colour assessments, blood pressure, height and weight and saliva samples for DNA. The lab analysis on samples from 43 blond and 42 dark-haired natives began in September 2010 and “within a week, we had our initial result”, said Kenny. “It was such a striking signal pointing to a single gene - a result you could hang your hat on. That rarely happens in science.”
The idea to study the genetics of the population came from co-author Sean Myles, a former Stanford postdoctoral scholar who is now an assistant professor at the Nova Scotia Agricultural College, after a trip there in 2004. “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 five to 10 per cent.’”
Dr Nic Timpson, one of the leaders of the project, said, “Naturally blond hair is a surprisingly unusual trait in humans which is typically associated with people from Scandinavian and Northern European countries. Whether this genetic variation is due to evolution or a recent introgression (the introduction of a new gene from another population) requires further investigation, but this variant explains over 45 per cent of the variance in hair colour in the Solomons.”
Co-author Carlos Bustamante, professor of genetics at Stanford, said the study gives good cause for more research on the genomes of rarely studied populations. “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,” Bustamante said.
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