Variability of skin colour: causes and implications

Melanin acts as a solar radiation filter. Genes are responsible for the amount and the type of the melanin produced, however also an UV radiation is able to induce a melanin synthesis. It appears that the UV radiation has been the determining factor in the human evolution to which the skin colour had to adapt. The original colour of skin was fair and pigmentation has developed after the loss of fur. High levels of UV radiation in equatorial Africa presented a selection pressure for dark pigmentation due to its negative effect on skin. On the other hand, it is important that the skin is bright enough so that a part of the UV radiation could pass through and launch the synthesis of vitamin D. When anatomically modern humans spread out of Africa, a decrease in pigmentation occurred in order to adapt for new levels of the UV radiation in new regions. Nutrition and sexual selection also have an effect on the formation of the skin colour but they have rather secondary importance. The variability of this trait is high between populations but very low within the populations, what testifies to a very intense natural selection. It has also been proven that there is a connection between civilization diseases, such as cancer. Differences in the skin colour have also been and still are important for social..