As the authors of “Skin Deep” state, “Our variation in skin color should be celebrated as one of the most visible manifestations of our evolution as a species.” I hope to enlighten you as to why they give creedence to that statement. It boils down to the authors concluding that various elements of natural selection, including reproductive health and migration, as well as cultural behaviors have influenced the variety of skin colors that we see today. To start with, the melanin in our skin protects us from UVB rays. The going census amongst scientists has been that darker skin adapted to have more melanin because of the need to protect ourselves from UVB rays, and getting skin cancer. While the authors think this contributed, they go a bit
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According to the authors, humans evolved in Africa over 100,000 years ago. In Africa it is very hot and there is a lot of UVB radiation. So when humans moved away from these high UVB areas we needed to adapt to be able to still synthesize vitamin D adequately. The authors guess that we did just that by slowly losing pigment over time. Michael Holick, from Boston University, did a study that spanned twenty years. His research concluded that not all sunlight contains enough UVB rays for our bodies to synthesize vitamin D. In Boston, for example, your body will not start producing vitamin D from the sun until March. The authors were also able to gather data that mapped out UVB radiation across the world. They discovered that there are three vitamin D zones: the tropics, subtropics, and temperate. The only zone that gets a consistent vitamin D supply all year is the tropics, and these populations tend to be darker skinned. The subtropical and temperate zones don’t get enough for at least a month out of the year, these populations of people tend to be lighter skin, but can still tan. The poles, never get enough all year, and the people living there tend to be pretty pale and burn easier. It is also important for us to note the exceptions to these rules. There are indigenous people, for example, living in Alaska
According to the authors, humans evolved in Africa over 100,000 years ago. In Africa it is very hot and there is a lot of UVB radiation. So when humans moved away from these high UVB areas we needed to adapt to be able to still synthesize vitamin D adequately. The authors guess that we did just that by slowly losing pigment over time. Michael Holick, from Boston University, did a study that spanned twenty years. His research concluded that not all sunlight contains enough UVB rays for our bodies to synthesize vitamin D. In Boston, for example, your body will not start producing vitamin D from the sun until March. The authors were also able to gather data that mapped out UVB radiation across the world. They discovered that there are three vitamin D zones: the tropics, subtropics, and temperate. The only zone that gets a consistent vitamin D supply all year is the tropics, and these populations tend to be darker skinned. The subtropical and temperate zones don’t get enough for at least a month out of the year, these populations of people tend to be lighter skin, but can still tan. The poles, never get enough all year, and the people living there tend to be pretty pale and burn easier. It is also important for us to note the exceptions to these rules. There are indigenous people, for example, living in Alaska