High levels of solar radiation can be dangerous to humans state of homeostasis. Melanin, which is a skin pigment responsible for protecting our skin from radiation, has two forms-pheomelanin and eumelanin, which come in different completions and sizes which determine skin color based on geographical location. For example, people who have more pheomelanin and less eumelanin result in having fair skin, putting them more at risk of the damaging UVA and UVB rays which cause various types of skin cancer that can even result in death. Likewise, people with the opposite composition of melanin result in darker skin which can also be negatively impacted by solar radiation. These people can have too much eumelanin which can severely limit their absorption of the nesecary amounts of UVB to produce vitamin A. If such an example should occur, it can result in pelvic deformations that inhibit child birth, rickets which softens bones in kids, and osteoporosis which make bones brittle and prone to breaking in adults.
However, humans are resilient and have found ways to prevent such damage. A short term adaptation, also know as a genetic response which will return to homeostasis shortly, is the appearance of a sunburn. The skin turns red from burning to warn us that we need to get out of the sun or find a remedy for the exposure.
Tanning is a facultative response in that the body temporarily changes its genetic expression so to protect itself from the radiation. This phenotype will return to its normal expression of pale skin when the stressors of intense sun is gone.
A developmental adaptation is the passing down of the eumelanin rich skin to offspring. Tribes in Africa exhibit this trait as it has helped them to survive natural selection this passing down to the current generations.
A cultural adaptation is in that fair skinned humans use sunscreen almost religiously to protect their skin from damage in sunny locations. This would be cultural as sunscreen is a tool and a social practice but not in a persons genetic make up.
Using these adaptations is a better way to understand race as it explains the human species variations as a result of our environments, not as an innate supremacy or marker of biological worthiness. That our visual differences are simply a result of our geography.
*I apologize for it being late, Time Warner had a wifi outage which didn't come back in time for me to submit it so I had to re-type it on my phone which was not fast enough.
Missing images? Is this related to your problem with the internet outage?
ReplyDeleteIn general, good balanced discussion on the problems related to solar radiation stress. One correction: UVB is important for production of vitamin D (the "sunshine vitamin"), not vitamin A.
Remember that adaptations must help the body in some way. That doesn't describe sun burns, which is evidence that the skin has been damaged. It doesn't help the body avoid further damage, particularly because by the time you realize you have a sun burn, the damage has already been done. Humans actually don't have a short term adaptation to solar radiation, which is why it is such a dangerous stress.
Very good discussion of both your facultative and developmental traits. Just wanted to note that light skin is also a developmental trait since it is an adaptation to lower levels of radiation, requiring lighter skin to allow for sufficient Vitamin D production.
Good cultural adaptation.
Good point that understanding why humans vary reveal that no particular race is superior to all others. We are all subject to the same stresses and forces, regardless of our external phenotypes. It is the ultimate leveler of humanity. But while this information is certainly valuable, can there be an applied benefit from this information? Can we use it to create tools and clothing that help us deal with solar radiation? Can the information be used for medical advancements in nutrition and cancer research?
Seems as if you have either combined the final two sections or you are missing one section? I recognize the reference to race so I'm thinking you missed the third section. This sentence is key with regard to race:
"Using these adaptations is a better way to understand race as it explains the human species variations as a result of our environments"
What you are referring to is a causal relationship between the environment and human variation, and you are correct that this causal relationship doesn't exist between race and human variation. If anything, variation caused race! Race arose as a social construct in the attempt to categorize humans based upon existing external phenotypic differences in human populations. Because race does not cause variation, it cannot be used to explain it.
Great post on how solar radiation negatively impacts the survival of humans by disturbing homeostasis. I never thought about how when we start feeling our skin burning under the sun as a way of our body suggesting a short term adaptation to which we should remove ourselves from the sun. I always just thought "oh its hot" I should get under some shade soon.
ReplyDeleteI wrote a good post it really explains the negative effects of solar radiation. You also met all of the requirements and was very clear about the different adaptations. Good job.
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