1. High levels of solar radiation negatively impacts the survival of humans through ultra violet radiation. Too much exposure to UV rays can cause cancer which, if untreated, can spread through out the body and become fatal. Also, UV radiation depletes folate - a B vitamin - which can disturb developmental processes in pregnant women. For example, a defect caused by a lack of folate is spina bifida.
2. Humans have adapted to this stress in four different ways:
- Unlike other environmental stresses high levels of UV radiation do not have a short-term adaptation. For example, if one became hot he would sweat to provide relief, but if one received high levels of UV radiation without the proper protection, he would get a sunburn. The sun burn is an indication to stay out of the sun more, but is not an adaptation.
- A facultative adaptation humans have adapted to combat excessive solar radiation by temporarily producing more melanin, otherwise known as tanning.
- A developmental adaptation that protects humans from UV radiation is skin color, which is determined by the level of pigment. Some one born with dark, deeply pigmented skin would not change skin color from environmental stresses.
- A cultural adaptation to high levels of UV radiation is the use of sun screen. Sun screen is a modern tool used to provide supplementary protection from the sun.
3. This information is useful for preserving health. Not only can it be used to preemptively avoid harm - such as sunburns, cancer, or folate deficiency - but it also can be used after damage is done. For example, if a fair skinned northerner moved closer to the equator, he would know to stay covered and pack lots of sunscreen. By studying the affects of UV radiation on varying populations we understand how much radiation is necessary and how much is harmful for differently pigmented skins.
4. Race, in terms of solar radiation, is only the measurement of pigment in an individual's skin. Therefore, a race can be classified as a population with similar adapted traits. In general, we know that populations evolved near the equator have more pigment than those farther north and south.
Thinking in terms of race has been an exaggerated, misleading distinction in the past. It is beneficial to think in terms of adaptation, because it eliminates any myths based on skin color; while others may think one is lesser than the other, we know it's just levels of pigment.
Excellent post and great catch on the fact that there really is not short-term physiological adaptation to solar radiation. Our bodies just can't respond quickly enough to protect ourselves from this stress in the short term.
ReplyDeleteOne caution: All individuals are capable of tanning, even those already equipped with high levels of melanin in their skin. It is just difficult to see the result of the tanning process.
Very good post.
In the summer I get just as red as the man in your first picture...it is not fun at all! I wish there was a short term adaptation to solar radiation because I am so over sunburns. Well sun block helps it does not always do its job to the fullest.
ReplyDeleteYour post was very well done but it would have been nice if you had gone into more detail about some of the adaptations. For example explaining exactly how tanning helps combat high solar radiation. Other than that i really enjoyed your post.
I enjoyed reading your post. It's interesting to know that dark pigmentation is overall protected from UV radiation. And those who are not as easily protected by the sunlight have adapted by using sunscreen.
ReplyDeleteGood job! I thought our bodies had a short term reaction to it just by producing melanin. But now I can see that they don't.
ReplyDeleteGreat post! I had never before considered tanning to be an adaptation, it was always something the lucky people got while I sunburned! Good job!
ReplyDeleteI loved the pictures you posted along with your blog, they helped get a visual and make connections!
ReplyDeleteBeing fair skinned I am one that can burn very easy. I constantly put on sunscreen when I am outside in the summer. This dry heat can really burn a fair skinned person quickly so protecting it is very important. my daughter on the other hand has a little darker pigment of skin than I do and she usually tans more than burns. I never understood why fair skin could not adapt to high levels of solar radiation.
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