Human Variation and Race Blog

The amount of exposure to high levels of solar radiation can be detrimental to the homeostasis condition of human physiology in many ways including uncomfortable burning of the skin, destruction of folic acid or folate, and the increase risk of skin cancer.  People who are at higher risk of these issues are people who have lighter skin pigmentation. This is because they, through evolution, produce a defective form of skin protein called melancortin- 1 receptor. This defective gene causes their pigmentation to be lighter allowing for less protection from ultra violet rays. While this is beneficial for the absorption of the necessary amounts of vitamin D, these people do not benefit from the same protections against the harmful aspects of high levels of solar radiation. The destruction of folate can cause anemia. The destruction of folic acid can cause birth deficiencies in pregnant women because folic acid is essential to the reproduction of DNA. With less protection from the ability to produce melanin people with lighter pigmentation are at greater risk of skin cancer like melanoma. Burning of the skin, increased risk of birth deficiencies and diseases such as cancer and anemia all can result in upsetting the homeostasis of human physiology making it hard for certain types of skin pigmented people to survive in environments that they were not evolutionarily adapted to. On the other hand, people who have darker pigmentation to adapt to living in places with high levels of solar radiation developed the ability to produce melanin in order to protect from the destructive properties of ultra violet rays. As darker pigmented people thrive in areas with a lot of UVB, these people suffer from the inability to produce vitamin D in areas that do not receive the high levels of solar radiation. This too can affect the homeostasis of the human physiology in that these people will develop weak bones due to the lack of vitamin D produced in their bodies.

Humans have adapted to dealing with high levels of solar radiation through four different methods: short-term, facultative, developmental, and cultural. Short-term adaptations for higher levels of solar radiation in the body’s physiology are hard to pin-point. Perhaps there really is not any short-term mechanism to defend the skin from high levels of solar radiation unless that population’s skin pigmentation already has large amounts of melanin. Other strategies for short-term adaptation may be something like seeking shelter or shade or simply covering the skin in an effort to protect it from solar radiation.

Shelter to protect from sun

Original origins had high levels of melanin

An example of facultative adaptation to higher levels of solar radiation in light pigmented people would be the increased amount of melanin in that population’s skin. The increase of melanin is considered a seasonal acclimatization in that melanin is increased in the summer and decreased in the winter. Melanin is the body’s natural defense against radiation from the sun. It gathers under the skins surfaces to act as a natural sunscreen against the harmful rays of ultra violet light. Specialized cells called melanocytes produces the melanin in response to radiation which can cause a change in the skins pigment generally a few hours after exposure. The increase in melanin is seen by a change in the skins pigmentation, tanning. Tanning is a facultative adaptive trait to help the body’s physiology to remain in a homeostasis state.

Skins reaction to seasonal climate change

Increase in melanin changing skin pigmentation

The next example of protection from solar radiation is through developmental adaptations. Develop adaptations to high levels of solar radiation is what produces the difference in skin pigmentation which constitutes the idea of race. The developmental trait of skin pigmentation to allow a certain degree of UVB to either penetrate or not penetrate a person’s skin   is an evolutionary trait that has been developed over a long period of time through natural selection to allow that person optimal survival ability in the environment in which they live. These traits are inherited through birth and are developed over generations. Evidence of this trend is seen in populations and where they live in respect to the equator. The populations who live closer to the equator experience a higher level of solar radiation. In response to this higher level of UVB, these populations develop darker pigmented skin through the level of melanin in their skin. The melanin acts as a natural sunscreen protecting these populations from skin cancer and the destruction of folate and folic acid in their bodies. People who live closer to the poles and experience less solar radiation over time developed lighter skin pigmentation in order for their bodies to receive more of the solar radiation in an effort to produce vitamin D. Since these populations live in an area that receives less radiation from the sun it is essential to optimize the absorption of the suns radiation in order to maintain a balance of vitamin D in their systems.

Human variation of skin pigmenation

Human variation of skin pigmentation in relation to where populations live

Lastly, cultural adaptations have been made to accommodate the different needs of different pigmented people. Dark skinned people have since moved away from the equator and light skin people have since moved closer to the equator which creates a awareness of how to culturally adapt to the new environments in which their skin pigmentation is not adapted for. Dark pigmented people adapt culturally to areas with less solar radiation in that they must find other ways to receive the necessary amounts of vitamin D. Since the Inuit people are relatively dark pigmented for living in a place with low solar radiation they had to find a way to ensure they were receiving the amount of vitamin D they needed. The Inuit people have adapted to their vitamin deficiency by eating a diet that consist of fish and large mammal blubber. Another cultural adaptation to the lack in vitamin D could be the production of synthesized vitamin D that people can take in a supplemental form. Light pigmented people who have moved to areas with higher levels of solar radiation have adapted culturally through the use of sunscreen and protective clothing in order to shield their skin from harmful radiation. Clothing such as breathable material, bathing suits, and large hats can all be seen as a cultural response to shield radiation.

Sunscreen

Protective clothing

Supplements

Large mammal diet

There are many benefits to studying human variation in their ability to tolerate solar radiation across environmental clines because the better understanding we have of our genetic make-up in response to environmental stressor the better we are to ensure maximum survival. The exploration of skin pigmentation in relation to solar radiation is very important to understand and appreciate. As a light pigmented individual it was interesting to see how genetically my ancestry evolved to allow the absorption of solar radiation in order for my ancestors to maintain the necessary levels of vitamin D needed to function.  The ability for my skin to tan is a fascinating way to see that my pigmentation can adapt facultative to help shield the destructive properties of solar radiation. Furthermore, for me and other light skinned individuals it is important to understand the damaging effects of solar radiation and know how to protect the skin from it. Conversely, it is equally important, and not so prevalent that darker pigmented people living in places with less solar radiation really need to be made more aware of the need for vitamin D in their bodies. Most people are aware of the damaging effect of too much solar radiation, but many are unaware of the damaging effect of too little solar radiation in darker pigmented people. This is an important aspect of the studying of human variation and environmental clines to ensure that light and dark pigmented people are aware of how to maximize their health in an environment they may have not been adapted to through evolution.

The reason why I picked this trait to explore is because it is the most prevalent signifier of race. Why is it that people from Africa are darker pigmented that the Norwegians? Why does the color of a person’s skin determine that person’s worth? Who claimed white skinned people to be superior to all other skin types? What does skin pigmentation have to do with politics, intellect, ability, social status, or wealth, when really skin pigmentation is an evolutionary result of a population’s ability to survive in the environment in which they inhabit? If race really had any significance to a difference in a person genetic make-up then why are all humans 99.9% the same? The only way race could explain the human variation in skin pigmentation is if race was another way of saying evolutionary changes in the level of melanin to maximize exposure or protection from solar radiation in respects to the need of a population in their relation to the equator. The study of evolution to environmental stresses is a way better way to study human variation rather than race because it allows us to see why populations from Africa have darker pigmentation. It allows people to understand that people with darker pigmentation developed that trait in order to withstand the environmental stressors in their area. The reason why Norwegians developed lighter pigmentation is so they could ensure they were able to produce vitamin D from the lower amounts of solar radiation in their environment. When human variation is studied through evolution, it is fascinating to see how evolution works through natural selection in order to increase a higher rate of survival. When looking at human variation through evolution, race is no longer relevant. Without race, racial discrimination is no longer relevant. Instead, people can understand the genetic make-up of a human body and its ability to endure environmental stressors, focusing their attention on biology rather than the physical differences which create false misconceptions of a person’s ability based on the color of his/her skin.