Researchers studying pigmentation in the South Pacific have uncovered a key genetic contribution to hair colour.

The findings, published in Science, reveal a functional 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.

Blond Solomon Islander (c. Sean Myles)

Human skin and hair colour varies considerably both within and among populations. Previous studies have shown that pigmentation is largely heritable but also suggest it has evolved to adapt to the sun’s ultraviolet rays — with populations near the equator possessing darker skin and hair colour.

However, the Melanesian population of the Solomon Islands, East of Papua New Guinea, differs from this trend.

The research – co-led by Dr Nic Timpson from the Medical Research Council (MRC) Centre for Causal Analyses in Translational Epidemiology at the University of Bristol and researchers at Stanford University in the US – sought to find out what has caused these islanders to possess such discordant patterns of pigmentation, some of the greatest in the world.

The team took samples from a pool of Melanesian participants, 43 with blonde hair and 42 with dark hair, and carried out genetic analysis to compare their genomes. The results showed that the across the whole genome, one key gene region contained the variation responsible for differences in the cells that produce darkening pigmentation, or melanocytes.

Naturally blonde hair is a surprisingly unusual trait in humans which is typically associated with people from Scandinavian and Northern European countries. The team’s 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.