Excess sun exposure, a diet rich in fish, and gene inheritance from ancient explorers and traders, are all possible theories why some dark-skinned indigenous Solomon Islanders are naturally blonde, according to new research published today in the journal Science.
The study, led by Stanford University researchers, found that 5 to 10 percent of the indigenous Solomon population have a gene that is responsible for blondeness. The trait, however, is distinctly different from the gene that causes blond hair in Europeans. Their findings reveal a genetic variant which has led the islanders to have simultaneously the darkest skin pigmentation outside of Africa and the highest prevalence of blonde hair outside of Europe.
Previous studies have proven that pigmentation is largely genetic but also has evolved to adapt to the Suns ultraviolet rays with populations near the equator having the darkest skin and hair color. However, the native Solomon Islanders differ from this trend.
This is one of the most beautiful examples to date of the mapping of a simple genetic trait in humans, David Reich, PhD, a professor of genetics at Harvard University, who was not involved in the study, said in a Stanford press release.
The research, co-led by researchers at Stanford University and Dr. Nic Timpson from the University of Bristol, sought out to find why these islanders possess such strikingly dissimilar hair and skin patterning in the world.
For the study, the team took samples from a pool of more than 1,000 Melanesian participants, 43 of which had blonde hair and 42 of which had dark hair. They carried out genetic analyses on the samples to compare their genomes. The results showed that across the whole genome, one key gene area contained the gene variation TYRP1 responsible for cell differences that produce dark pigmentation.
TYRP1 is known to influence pigmentation in humans. But the researchers found the variant of TYRP1 that causes the blonde hair in Solomon Islanders is entirely absent from the genomes in Europeans.
Here you go into an unstudied population with a small sample size and you can really find some cool things, said study coauthor Carlos Bustamante, a geneticist at Stanford Universitys School of Medicine. So what about other places, like what about light pigmentation in parts of Africa? How do we not know the genetic basis of skin and hair pigmentations across the globe?
Naturally blonde hair is a surprisingly unusual trait in humans which is typically associated with people from Scandinavian and Northern European countries, said Timpson. Our findings help explain the fascinating differences in these physical characteristics, but also underline the importance of genetic mapping using isolated populations to help shed new light on the epidemiology of disease.
Many experts believed the blonde hair of Melanesia was the result of a trait passed on by Europeans who visited the islands centuries ago.
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Blondeness In Solomon Islanders Due To Genetic Variations