A new study of the people from the Solomon Islands in Melanesia, a group of islands northeast of Australia, has shown that blond hair evolved differently, genetically speaking, than in Europeans. About 5-10% of the people in Melanesia have naturally blond hair, which is the highest prevalence outside of Europe.
This refutes the hypothesis that blond hair was introduced by colonial Europeans. Carlos Bustamante, a geneticist at Stanford University School of Medicine, in California, and his team published their findings in the journal Science.
Bustamante and his colleagues compared the genomes of 43 blond and 42 dark-haired Solomon Islanders. This revealed that the blond hair was strongly associated with a single mutation in the TYRP1 gene, which encodes an enzyme that influences pigmentation in mice and humans. In Europeans, several genes are known to contribute to blond hair, but TYRP1 isn’t involved.
They compared DNA between more than 900 Solomon Islanders and 900 other people from 52 populations around the world to find that the TYRP1 mutation is probably unique to the Oceanic region that includes Melanesia. About one-quarter Solomon Islanders carry the recessive gene, so two copies are needed to have blond hair.
However, not all occurrences of blond hair are the result of this particular mutation, but researchers have predicted that it accounts for about 30% of cases. Another 16% are attributed to age and gender (young children and women are more likely to have blond hair), while the rest is attributed to sun exposure and other undiscovered genes. It’s unusual that one specific mutation accounts for such a large proportion of an observable trait in a population.
Bustamante thinks that this mutation might have arisen between 5,000 and 30,000 years ago, but hasn’t been able to explain why it has reached such a high frequency in the Solomon Islands.