May 06, 2004
Evolution of Human Skin Color Coloration
American Journal of Physical Anthropology
Early View (Articles online in advance of print)
Geographic distribution of environmental factors influencing human skin coloration
George Chaplin
Skin coloration in indigenous peoples is strongly related to levels of ultraviolet radiation (UVR). In this study, the relationships of skin reflectance to seasonal UVR levels and other environmental variables were investigated, with the aim of determining which variables contributed most significantly to skin reflectance. The UVR data recorded by satellite were combined with environmental variables and data on human skin reflectance in a geographic information system (GIS). These were then analyzed visually and statistically through exploratory data analysis, correlation analysis, principal components analysis, least-squares regression analysis, and nonlinear techniques. The main finding of this study was that the evolution of skin reflectance could be almost fully modeled as a linear effect of UVR in the autumn alone. This linear model needs only minor modification, by the introduction of terms for the maximum amount of UVR, and for summer precipitation and winter precipitation, to account for almost all the variation in skin reflectance. A further significant finding was that the effect of summer UVR seems to reach a threshold beyond which further adaptation is difficult.
Posted by Dienekes at May 6, 2004 05:44 PM | PermaLinkHi,
I'm interested in using methods of GIS to investigate relationships between environment and polytypic species and was wondering if you could answer a question about your research summarized on this webpage?
How did you go about accounting for the vast amounts of shade in any given geographic area? What can be input into the database or factored into the statistical analyses so that the results address the fact that most species of mammals seek shade for a good portion of each day?
This is a problem for me in trying to address the extreme differences in human skin reflectance among different geographic locations and at the same time, address the reality that even among hunter/gatherer societies daily activities do not include exclusive hours spent in the blazing sun.
Also, I come upon problems in addressing the fact that dark skin is prevalent even among those peoples who live in the deep shade of the forest.
I thought maybe you might have included ways to address these issues in the full article (which I have not seen).
Thank you for any input you can send my way.
R. Savoy
Posted by: R. Savoy at May 25, 2004 03:51 PM