The Evolution of Human Skin Color
Humans are characterized and categorized according to skin color due to its conspicuity. It is visibly adaptive to temperature and occurs in different variations over a given species. It is this variance that drives the research on the evolution of human skin color.
According to Nina G. Jablonski, genetic modification is the principal cause of variation in skin pigmentation. About 3 to 2 million years ago bipedal hominin body hair started disappearing to allow for better dissipation of heat through sweating. About 1.5 million years ago, about the time of the Homo heidelbergensis, the earth endured a megadrought that drove early man to the open landscapes arid and semi-arid areas in search for food.
This exposure to the open landscape meant direct exposure to the sun and it radiation. This meant that early man was prone to the Ultra Violet- B radiation. Ultra violet radiation is essential for the synthesis of Vitamin D; however, long exposure causes health problems and skin damage. Jablonski, therefore, bases her argument on this exposure to sunlight, to explain that skin pigmentation was a result of exposure to direct sunlight, to protect the early man from folate depletion and epidermal permeability barrier.
It is due to the evolution of early man to hairless skin that resulted in the development of melanin. Lack of melanin causes albinism. Melanin is adaptive and usually increases or decreases in the skin based on exposure to sunlight. Its central role is to protect the skin from tissue damage. Recent studies prove this observation by correlating skin reflectance and Ultra Violet levels. The result showed that the highest correlation was near the absorption level of ox-hemoglobin, which suggests that melanin reduces the effect of UV. Epidermal melanin occurs in different forms on different parts of the body and UV radiation has a different impact on all of this sections. Melanin works as an optical and chemical filter attenuating radiation by scattering while absorbing compounds produced photochemically.
Studies also show that females tend to be more lightly skinned than males. These genes of human coloration pass down from one generation to another leading to the diverse nature of human skin color in the contemporary world. It is for this reason that human pigmentation cannot be used in determining phylogenetic relationships among humans in the modern world.