Viviana HerreraAssignment #3What makes a person black or white? There is a substance that our body produces naturallycalled Melanin. This substance is the responsible of our skin pigmentation. The principalfunction of Melanin is to act as a heat absorber. The quantity of melanin produced by our bodydepends on our geographic location. First humans on earth appear in Africa and they developeda darker skin to protect themselves from their environment. It is well known that people wholives in zones were the sun has less impact (poles), tend to have a lighter skin than people wholives in areas were the sun falls more directly. If the radiation is higher the person will develop ahigher quantity of melanin in his body and as a result would have a darker pigmentation.However, this only answer the reason why some people have different skin color. It does notanswer the question of why do we need to produce melanin. The article “Re-appraisal of current theories for the development and loss of epidermalpigmentation in hominids and modern humans by Elias and Williams tries to explain why therewas a loss in epidermal pigmentation producing different races of people. The authors mentionprevious theories that tried to explain this phenomena. One of the most known is the one thatargues that the production of melanin is related with the production of vitamin D and that itevolves to prevent vitamin D intoxication. Other theories argue that the reason of the evolutionof melanin is to prevent skin cancer, folic acid deficiency or to protect the person form the UVradiation. Nevertheless, the authors discard all those theories because there are not enoughevidence to support it.Viviana HerreraInstead, the reason why melanin evolved in our body is related with protection. Dark skins arestronger than light skins. They are more resistant to infections. This is because darker skins tendto be drier. Microbes can only colonize humid places and if the skin is dry bacteria will notattach to the person. The environment is crucial, and in dry places like Africa, it is required tohave a permeable skin to avoid dehydration. We know that homeostasis is the process of naturaltemperature regulation of our bodies. When it is too hot we sweat in order to release the heat andget fresh. However if your skin lets the sweet go away you can suffer from dehydration. In sucha dry and hot environment when people has to hunt and move, it was necessary to develop a skinwho can maintain the body fresh by sweeting but not sweeting too much in order to avoiddehydration. When people started to move to different environments where this kind of skin wasnot necessary to survive anymore, natural selection favorite the lighter skins. In addition they explained pigment dilution as a result of “positive selection for lighterpigmentation” (Elias, Williams). They also argue that Vitamin B is not the cause of pigmentdilution, given the fact that people can consume vitamin D by eating certain foods, and that evena short exposition to the UV radiation can create enough vitamin D storage for a year nondepending on your skin color. They also discuss the fact that there is a protein that is in chargeof enhance vitamin D production. Finally the end up with the conclusion that the production oflighter skins is product of mutations based on the diet of the