2. An example of a short term adaptation humans have to cope with high levels of solar radiation is perspiration. One loses heat through many sweat glands in evaporative cooling. Perspiration is considered to be the “most important factor in heat dissipation” according to the book.
An example of a facultative adaptation is acclimatization including tanning. The physiological responses to this environmental stress is influenced to an extent by genetic factors, as well as other factors like duration and severity of the exposure. The simplest form of acclimatization is tanning, which is a temporary and quick environmental change adjustment that returns back to the original skin tone over time when exposure to sunlight is reduced.
An example of a developmental adaptation is the presence of the pigment called melanin. The number and size of melanin particles as well as the percentages of different kinds of melanin determine skin color. If someone has a higher percentage of pheomelanin their skin will probably be more red to yellow color, and those who have a higher percentage of eumelanin will probably be more dark brown to black colored.
Examples of cultural adaptations are sunglasses, hats, clothes and sunscreen. Before people spend a day in the sun, they will usually apply sunscreen to prevent or reduce risk of skin damage and tanning. People also wear sunglasses, hats and extra clothing (beach cover-up) to protect themselves from solar radiation.
3. It is beneficial to study human variations from this perspective across environmental clines because it helps to show why certain people have health problems, or are healthier than others or have the skin tone they do, or why it is beneficial to have the skin tone that they do. By looking at the clines of solar radiation (where melanin is protective) versus clines of solar vitamin D absorption (where melanin is not protective) it shows that in areas where UV protection is needed, skin color is darker, and where people need more vitamin D more than they need UV protection, their skin is lighter. By using UV radiation as a factor in studies like malnutrition among children indicating high frequencies of rickets disease, or vitamin D related to healthy pregnancies, it can be useful to figure out that certain people need more vitamin D, or need to be in the sun less or more to be healthier. In a study published in the Journal of Nutrition, researchers found that prenatal vitamins should contain higher doses of vitamin D, especially in the northern US. 16% of African Americans and 53% of European Americans had enough vitamin D in their bodies at the end of their pregnancies. Therefore, the information that was gathered from UV rays’ connection with vitamin D, and anthropological studies became the basis of further research for human nutrition and pregnancy.
4. Race is influenced by levels of solar radiation, especially in the developmental adaptation of the presence of melanin. Race is the result of the adaptations, especially those that are genetic and longer lasting. Race is the result of different environmental clines and the different makeup of melanin in individuals. It is one of the many adaptations to deal with high levels of solar radiation. The study of environmental influences on adaptations is a better way to understand human variation than by the use of race because race is the result of many different adaptations. These adaptations are what is a key to these major variations and changes in the appearance and makeup of humans. Environmental influences are what must be studied in order to learn about why there is variation among humans, especially skin color. It is interesting to learn why there is variation, because it shows that our bodies are influenced by many simple things that we wouldn’t even think of like the sun or altitude.
Very thorough discussion and your discussion on the benefits of studying variation using clines was excellent.
ReplyDeleteTwo points:
Perspiration helps to address heat stress, not solar radiation. There really isn't a short term adaptation to solar radiation which is why it is such a dangerous stress for those with low basal levels of melanin.
I have to argue with your suggestion that "Race is the result of adaptations.". Race is a cultural and social construct having everything to do with human perceptions and bias and little to do with biology. That is why it can't be used to study biology. It is too easily subject to bias and stereotypes.
After looking at my comments, I was curious to see what you had done for your post. The picture for the tanning adaptation is cool as you can see the difference. I was wrong and sunburning is not part of adaptation as it is reacting to it, adaptation would be in the form of tanning. Also, I did mention the sweating as I saw you did. I didn't even think of the adaptation we do when it comes to hats and sunglasses, but it is very true that we do it because of the solar radiation. I liked your post and felt it had really good points.
ReplyDeleteGreat Post! It was loaded with tons of great information about solar radiation effects. There is one thing that stood out though. You said something about race is the result of many different adaptations. I think you have race mixed up with skin complexion. They are two totally different things. My family is from Belize, which is located in Central America. We have dark skin complexion but our nationality is Hispanic or Latin American not Black or African American. Race is very bias.
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