As a small child perusing old physical anthropology books I would occasionally stumble upon images of people of Oceanian stock with light hair color. I would wonder: is this a biological or cultural feature? In other words, were people bleaching their hair? If it was biological, was it heritable, or was it simply malnutrition? Another aspect of the phenotype was also straightforward: it did not seem that light hair color resulted in any concomitant lightening of the skin. Granting that this was a heritable biological trait, the questions then were simple: was this trait an independent occurrence of de-pigmentation in Oceania, or was it due to introgression of European alleles?
First, one must note that this is not an isolated feature in Oceania. Rather, blondism crops up in the Solomon Islands, in New Guinea, as well as among some Australian desert groups. This in itself should make us skeptical of the model of European admixture. Additionally, blue eyes, which exhibits a higher frequency in Europeans than blonde hair, is not similarly common in these populations. But all this speculation is now a historical curiosity. The results are widely known from conference presentations that have been reported, but finally the paper is out in Science which solves the “riddle” of hair color in Oceania at the level of genetic causation.
Naturally blond hair is rare in humans and found almost exclusively in Europe and Oceania. Here, we identify an arginine-to-cysteine change at a highly conserved residue in tyrosinase-related protein 1 (TYRP1) as a major determinant of blond hair in Solomon Islanders. This missense mutation is predicted to affect catalytic activity of TYRP1 and causes blond hair through a recessive mode of inheritance. The mutation is at a frequency of 26% in the Solomon Islands, is absent outside of Oceania, represents a strong common genetic effect on a complex human phenotype, and highlights the importance of examining genetic associations worldwide.
I have posted on the existence of blonde hair amongst some Melanesians before. There are natural chemical treatments as well as extreme malnutrition which can result in blonde hair in dark skinned people. The latter seems unlikely from the photos I’ve seen (the lightening of hair due to lack of food has been reported in African refugee camps). In regards to the former I’m confused as to why chemical treatments would be common among Oceanian people as disparate as Solomon Islanders and central desert Australian Aborigines, and yet not among many other east Eurasian populations.
Recently I was looking for images of the alpine biomes of the New Guinea highlands* and stumbled onto some intriguing, though not entirely surprising, set of photographs of individuals from Papua New Guinea. They were noteworthy because they manifested the conventional Melanesian physical type, but their hair had a blonde cast to it. For example, here is a charming blonde boy. The photographer has several other striking portraits of Melanesians with lighter hair at his website. In regards to the peculiar hair color of these people he says: “When you ask the people why there are so many blonde people on the islands, they answer 3 things: they have white ancestors, they receive too much sun, or they do not eat enough vitamins! – Langania village, New Ireland, Papua New Guinea.” There is more discussion in the comments about this issue, some claiming that likely it is the sea water and sun which is producing bleaching naturally. If you look around you will see references to bleaching of hair among some of these people as a cultural trait, though the references tend not to be concrete (many clearly assume they’re bleaching their hair, rather than reporting bleaching). The blonde being at the tips from what I can tell in some cases I certainly don’t reject the explanation that bleaching is a cultural practice among these peoples, albeit for children and women only.
But the peculiar hair color of these populations is noted in the scientific literature as if it is a biological characteristic of these groups, not a cultural artifact. From Molecular genetic evidence for the human settlement of the Pacifc: analysis of mitochondrial DNA, Y chromosome and HLA markers: “The Tolais of New Britain are phenotypically ‘Melanesian’, with fairly dark skin and frizzy hair, some-times almost blonde as in some highland Papuan groups.” Enter Tolai ‘New Britain’ into Google Images and the first few pages have several instances of blonde children, including this cute triplet.