Natural Selection is Furthering Mutations That are Making Skin Paler

Source: (Science Daily), University of the Basque Country
Link: http://www.sciencedaily.com/releases/2014/12/141205100058.htm
Date: January 9, 2015

Summary:

     Human skin color varies according to the latitude and, therefore, according to the intensity of ultraviolet light. Individuals living at low latitudes generally have darker skin, whereas those living at high latitudes have paler skin. It has been determined that evolution is furthering mutations that are lightening the skin, probably owing to the need to synthesize vitamin D at latitudes where there is reduced solar irradiation. However, in turn, this increases the probability of developing melanoma or other types of skin cancer. Natural selection furthers certain mutations so that individuals can have paler skin, since at certain latitudes having a skin with a dark pigmentation prevents the synthesis of adequate levels of vitamin D, essential for survival. Vitamin D can be obtained through the diet, but also in an indirect way as UV light passes through the skin. Dark skin contains the pigment melanin, which acts as a barrier and prevents UV rays from penetrating. At high latitudes where the intensity of UV light is very low, this is a problem, as insufficient quantities of vitamin D are synthesized.

     Why does natural selection further a mutation that causes cancer? Vitamin D is essential for skeletal mineralization and development, and the lack of this vitamin can lead to various problems in children's health. Yet the skin cancer melanoma is a cancer that tends to appear in adult life, following the reproductive phase. Theoretically, as these adult individuals have by now produced offspring, they are no longer important in evolution. 

Relevance: 

     

     This topic relates to what we are learning about evolution in Chapter 14. This article relates to natural selection, the process whereby organisms better adapted to their environment tend to survive and produce more offspring, which we have talked about in class. Darwin's theory of "Descent with Modification" presented in Chapter 14 states that over time and generations, traits providing reproductive advantage become more common within a population. This directly relates to my article, in which over time, human skin depigmentation has occurred due to the need to synthesize vitamin D. This has occurred due to the process of natural selection, in which individuals who carry the trait for paler skin have a higher chance of surviving and passing on this trait to their offspring at higher latitudes, where there is less solar irradiation.