Evolution of Skin Pigmentation

Publication: Re-appraisal of current theories for the development and loss of epidermal pigmentation in hominins and modern humans.
Elias PM, Williams ML. J Hum Evol. 2013 Mar 8. [Epub ahead of print]

Synopsis and Significance: In this paper we propose that the evolution of dark skin pigmentation in human ancestors was driven by their need to preserve body water in the hot and dry climate of the equatorial African savannah. This, the most critical function of skin, is provided by the skin’s permeability barrier. Dark pigmentation generates a superior barrier and allowed these hominins to leave the forest and hunt on the hot, dry savannahs with a lesser risk of dehydration.

We further propose that this theory is in greater concordance with reproductive fitness and with skin biology than the more widely espoused theories for the evolution of pigmentation, such as protection from genotoxic effects of sunlight and/or from photodegradation of folic acid.

Contrary to the prevailing hypothesis that pigment was subsequently lost to allow more sunlight to penetrate and to stimulate vitamin D3 production by the skin, we note that modern humans, who left Africa for northern climes, no longer needed the effects of melanin on their skin barrier competence, because they now resided in colder and moister habitats. We propose that production of melanin was reduced over time as a form of metabolic conservation – to save energy for more urgent needs.

Copyright © 2013 Elias and Williams

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