The Case of Melanin in Melanesia

Recently my attention has been focused on the large number of books that are crammed into, onto, next to, and in all sorts of direction, on my bookcase. The books range in subject-matter but the majority of them do have a link with Papua New Guinea. The most recent book that’s perked my interest is Nina Jablonski’s 2006 book Skin: A Natural History, in which Jablonski offers a comprehensive discussion on the largest human organ and its’ most visible – skin.

What really made me take notice of Jablonski’s book was its discussion on the evolution of skin colour and its’ relationship with ultraviolet radiation and consequently, one’s location on Earth.  Obviously, trans-migration and intermarriage have begun to dissolve the traditional regions of colour in the world, but there still remains certain pockets of people where not much has changed over the centuries. One such place is Melanesia.

When one talks about the colour of skin within Melanesia, there is no doubt where the darkest people of the region are located. The people of Buka Island, Bougainville and the western provinces of Solomon Islands including Western Province and Choiseul are distinctive because of their pigmentation. I remember as a child wondering how the Bougainvillean people were so dark – so dark that it has been argued that they constitute the darkest race in the world. Well, there is a reason, and as alluded to above, it’s all to do with the relationship between ultraviolet radiation and one’s location – and a couple centuries to incubate the evolution of skin pigmentation.

Jablonski uses interesting data from NASA’s 7 TOMS (Total Ozone Mapping Spectrometer) Satellite to show the regions in the world that receive the annual average ultraviolet radiation. See the snapshot below:

The pink and red spots indicate the areas in the world that receive the most ultraviolet radiation, and as suspected, those areas lie along the Equator. What’s interesting is the patch of pink right above Bougainville and Solomon Islands. Now taking into account the changes in the ozone layer courtesy of the industrial age, one could assume that patch of pink may have sat right above the Solomon Archipelago for hundreds of years, directly affecting the people who migrated there and whose descendants we are now familiar with.

Taking the above data and applying a multiple regression analysis, Jablonski predicts what the future of skin colour on Earth may look like, and it seems a number of currently ‘white’ countries are in for a permanent tan, including Australia. See the image below:

As stated in the image, human skin colour is the product of evolution by natural selection, however, not everything is good news – particularly for those people who have migrated, or are the products of migration. It is no coincidence that the skin cancer rate in Australia and New Zealand is one of the highest in the world, simply put, the majority of Australia and NZ’s  population are not biologically designed to be living in such UVR hot-spots and the cancer statistics do provide evidence supporting Jablonski’s discussion.

~ by Tavurvur on August 10, 2009.