Question: Why have humans evolved to have different skin colors?
Rationale: As time progressed humans became more and more intelligent. As their brain sizes grew, they were able to manipulate new habitats and they were able to live in different regions. At the beginning, we were suited for a particular habitat, but we became increasingly more intelligent and we were able to occupy different habitats. We were originally suited for areas of high sunlight very close to the equator but we slowly started to disperse and as we began to move to new locations, we slowly began to adapt to them. Having a dark pigmentation at high latitudes would be a disadvantage. Why it was necessary for humans to evolve different skin colors as they began to disperse, and especially how did geographical location play a role in this?
Mittelstaedt, M. 2007 Evolutionary Adaptations: The Impact of Lighter Skin, Historical Newspapers, ProQuest Historical Newspapers: The Globe and Mail (1844-2011) Martin focuses on the variation between skin color of people who live at high altitudes and people who live closer to the equator. …show more content…
He explains why it is better for people to have lighter skin colors if they live at higher altitudes because it allows to make more Vitamin D. At high altitudes there is not much sunlight. Melanin acts like a natural sunscreen. The darker your skin color the more melanin you have, so the less sunlight you will be able to absorb. The UV from the sun allows for the production of Vitamin D. This is an evolutionary adaptation that is advantageous because the different pigmentations in skin color either protects people from UV rays or the levels of pigmentation would allow them absorb more sunlight therefore making more Vitamin D. It has been found that it takes people of lighter complexion to make the same amount of Vitamin D from the sun one-sixth of the time that it takes people with a darker complexion such as African American. Sulem, P, Gudbjartsson, D. F., Stacey, S. et Al. 2007. Genetic determinants of hair, eye and skin pigmentation in Europeans. Nature Genetics, 39(12), 1443-52. doi:http://dx.doi.org/10.1038/ng.2007.13 This article focuses on the evolutionary signs, that it is the pigmentation of Europeans and East Asians that have changed. This is important because it is believed that we all once has darker skin tones and have adapted to have lighter skins, because in some cases lighter skin tones would be more advantageous. Different pigmentations is due to mutations in different genes. Genes such as KITLG and TYR are proposed to be the genes that contribute to pigmentation. Some strong evidence for this theory of humans adapting to have lighter skin colors include the findings that there are in fact some genes that help with the synthesis of eumelanin and this is under “strong selection” in regions closer to the equator, meaning more UVR. The article points out that it is positive selection which is the cause of lighter skin tones, especially those of European and East Asian ancestry. They also focus on some of the advantages of lighter skin, the main one being synthesis of Vitamin D3. Those with lighter skins can still synthesize Vitamin D3, even though there is little sunlight. The article also talks about the advantages of having darker skin color, which would be protection against cancer, but goes on to explain why it would be more advantageous to have a