Human Variation & Race

Human Variation & Race

Solar radiation impacts the survival of humans with too high or too low of levels of exposure. Solar radiation is needed for the body to receive Vitamin D. Having inadequate amounts of Vitamin D can contribute to high blood pressure, weakened protection of UV rays, and lack developmental factors such as skeletal deformities. Overexposure of UVB radiation can cause damage to the DNA. UVB radiation is directly absorbed into the cells by the DNA which can cause skin cancer. This damage at the genetic level disturbs homeostasis and is life threatening to the species.

 

Humans have adapted to higher levels of solar radiation in many ways, and there are many factors of the adaptation. Unfortunately, we do not have a short term adaptation. When there is too much exposure to solar radiation, the skin burns.

Melanin is 1 out of 3 factors that alter skin color to assist with protection from the UV exposure by absorbing the UV (ultra-violet) radiation that causes genetic mutations. The melanin production is a result of facultative adaptation – tanning. Tanning is the result of temporarily increased melanin production caused by exposure of solar radiation. For some individuals, their skin tone changes from the summer months to the winter months when there is less exposure. This response occurs in all humans except for Albinos who carry a genetic mutation that prevents their melanocytes from producing melanin.

This leads to the developmental change. Individuals that have had a higher exposure to solar radiation tend to have a darker complexion due to the increased production of melanin. Individuals located in warmer climates such as the tropics tend to wear less clothing due to the heat; therefore, their skin is more exposed to the solar radiation. Over time, these individuals will produce more melanin and they will have a darker skin tone. Individuals whose cells do not adapt to the change become more likely to develop life threatening skin cancers. Individuals that are in northern locations tend to have a colder climate which requires them to wear additional clothing. The additional clothing blocks the UV exposure which does not allow the melanin to produce as rapidly as those in warmer climates. The lack of melanin leaves these individuals with a fair skin tone.

There are many cultural adaptations to high solar radiation. There is the old fashioned way of protecting ourselves – shelter and shade, and then clothing. There are also the advanced methods like sunglasses and umbrellas, and most importantly, sunscreen. Although sunscreen doesn’t keep someone completely protected, it allows individuals with fair skin to be exposed for a longer than normal period of time without causing damage.


The benefit of studying across environmental clines is to see how different people adapt to certain environmental influences. If we studied only one environment, we wouldn’t be able to see the positive and negative impacts of solar radiation. For example, if we were to only study the hotter climates, it would be much harder to discuss the effects of sunburns and skin cancer, or how the melanin protects the skin. The different adaptations can be used to resolve some of the health issues we see today. Being able to see the impact across different cultures provides us with a better understanding as to how much solar radiation is a healthy amount.

 

Using race to understand the variation of the adaptations of solar radiation allows us to look at the specific differences between the races to see how each one’s traits are beneficial to their environment; however, the study of environmental influences is better. Although we can study the different races to see how each one is better suited for their environment, if we study the environment, we can see how these individuals adapted to fit their environment.