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Pacific islanders' blonde hair evolved independently from Europeans'

15 May 2012
Appeared in BioNews 656

The genetic cause of blonde hair may be different in populations in Europe and Oceania, researchers have found. A single mutation in the TYRP1 gene, which is not associated with blonde hair in Europeans, was found in around a quarter of Solomon Islanders and is believed to be major determinant for the pigmentation. The findings suggest that blonde hair may have evolved independently in Melanesian and European populations.

Between five and ten percent of Solomon Islanders have naturally blonde hair - yet the population also has darkest skin pigmentation outside Africa. Using a genome-wide association study researchers from the Stanford University School of Medicine, USA, compared the genomes of 43 blonde and 42 dark-haired Islanders.

The findings, published in Science, reveal that a single mutation in the TYRP1 gene, which is involved in the hair and skin pigmentation process in humans, distinguished those with blonde hair. The mutation is recessive and so two copies are needed for a person to have blonde hair.

However, it was not the only factor the researchers believe accounted for blonde hair. Around 16 percent of cases were attributable to age and gender, they said. The mutation was not found in the samples obtained from outside the South Pacific, demonstrating it is likely to be particular to the region.

Naturally blonde hair is rare, occurring in primarily Northern Europe and then Oceania, where the Solomon Islands are located. 'We originally thought, well that must be a Captain Cook allele', says Professor Carlos Bustamante, from Stanford University. However, contrary to previous beliefs, it would seem that the gene is unlikely to have originated in Europe.

The researchers are unsure of why this genetic mutation thrived in the Melanesian population - so far there is no evidence that blonde hair would have provided an evolutionary advantage. The research team suggests that the TYRP1 mutation is responsible for around 30 percent of all instances of blonde hair in the Melanesian population, allowing for other explanations such as gene flow, sun exposure and other undiscovered genes.

This project also highlighted the importance of including minority populations in gene mapping. Professor Bustamante explained: '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'.

'Before this, everybody would have thought that blonde hair evolved once in humans. This tells us we can't really assume that even these common mutations are common across different human populations. Non-European populations are critical to study to find mutations that may be underlying the vast phenotypic variation of humans'.

SOURCES & REFERENCES
Blonde hair evolved independently in Pacific islands
New Scientist |  3 May 2012
Blonde hair evolved more than once
Nature |  3 May 2012
Melanesian Blond Hair Is Caused by an Amino Acid Change in TYRP1
Science |  4 May 2012
Naturally blond hair in Solomon Islanders rooted in native gene, study finds
Stanford University press release |  3 May 2012
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