Solar radiation impacts the survival of humans if the
level of exposure is too high or too low.
Of course, solar radiation is needed as a source of Vitamin D. Having
inadequate amounts of Vitamin D can contribute to weakened protection from UV rays,
high blood pressure, and developmental factors such as skeletal deformities.
Overexposure of UV radiation can cause damage to the DNA. UV radiation is
directly absorbed into the cells by the DNA which can cause skin cancer. Also, UV radiation depletes folate - a B
vitamin - which can disturb developmental processes in pregnant women and
result in the defect spina bifida. This
damage at the genetic level disturbs homeostasis and is life threatening to the
species.
Unfortunately, humans do not have a short term
adaptation to over exposure to solar radiation.
However, humans have adapted to higher levels of solar radiation in many
ways, and there are many factors of the adaptation.
A facultative adaptation humans have adapted to combat
excessive solar radiation is by tanning, and temporarily producing more melanin.
A developmental adaptation that protects humans from
UV radiation is skin color. Melanin is
one of three factors that alter skin color and assists with protection from UV
exposure by absorbing the UV radiation that causes genetic mutations. Individuals that have had a greater exposure
to solar radiation would tend to have a darker complexion due to increased melanin
production. Whereas individuals located in
areas where they have less exposure to UV radiation, or limited exposure due to
other conditions (more clothing due to colder climates), would have a lesser
amount or lack of melanin, resulting in a lighter or fairer skin tone.
Cultural adaptations to high levels of UV radiation can
be the use of shelter and shade, clothing, and of course the use of sun screen.
Sun screen is a modern tool used to provide supplementary protection from the
sun. Although, sunscreen isn’t complete
protection, it does allow for longer UV exposure without damage.
The benefit of studying across environmental clines is to see how different people have adapted to different environmental influences. If we only studied one environment, we wouldn’t see the whole spectrum of solar radiations impact. By studying the effects of UV radiation on varying populations we understand how much radiation is necessary and how much is harmful for differently pigmented skins. This information is useful for preserving health and can be used to preemptively avoid harm, such as sunburns, cancer, or folate deficiency.
Using the study of adaptations to environmental influences is a better way to understand human variation, because as we have learned, adaptation to environmental influences and mutation are the causes of the variation.
Good balanced discussion on solar radiation, both with the dangers of too much and too little.
ReplyDeleteCorrect, humans do not have a short term (physiological) adaptation to radiation, which is why it is so dangerous.
Good explanation of your facultative adaptation.
Your explanation for your developmental adaptation explains why populations at equatorial areas have darker skin, but why shouldn't populations at higher latitudes keep that darker skin just to be safe? Is there another reason why they need lighter skin other than the explanation that they can have lighter skin with lower radiation levels?
Good cultural adaptation.
Clear discussion the benefits of the adaptive approach.
"Therefore, if you must use the term race, it would be defined as a population with similar adapted traits"
Okay... but that isn't how race is defined. We need to consider the term as it is defined, not recreate the definition to suite our purposes. So given that race is a sociocultural construct, not a biological one, would you argue that it has no function in explaining human variation? Or do you think it is still useful?
Other than this last point, good post.
Given the current sociocultural definition of race, I would argue race would be of no use or function in explaining human variation. Migratory patterns, environmental pressures and human adaptation would be best in explaining human variation.
ReplyDeleteAgreed. There is also the problem that each culture has its own subjective definition of race. So which definition would we use to objectively study biological variation? None of them.
DeleteThank you for the response.
My knowledge on the different definitions of race by different cultures is extremely limited.
ReplyDeleteAs I understand them, the definition of race here in the U.S.is based primarily on skin color, while the definition in western and central European countries is more nationalistic (in that they don't judge someone based on the color of their skin, but by their country of birth), and Asian countries base race more regionally.
As stated, my knowledge is lacking on the definitions prescribed to by other cultures.
Based upon my limited knowledge of the criteria, I have to say that race is not an adequate tool to use to objectively study biological variation.