Human Variation & Race Blog Post
High Levels of Solar Radiation
Although beneficial in aiding the production of vitamin D
within humans, high levels of solar radiation negatively impacts the survival
of humans by disturbing homeostasis, or more specifically, damaging and/or
rapidly changing skin cells. This damage can begin as a sunburn, and has the
potential to be more destructive each time a sunburn occurs. Which later can result in
chronic hyper-pigmentation, or even cancer.
Humans have developed a short term adaptation to high solar
radiation-the reddening of the skin, in varying degrees up to and including sunburn.
Another adaptation to solar
radiation of a more facultative nature is tanning. When one is exposed in
shorter lengths of time to solar radiation, melanin synthesis occurs,
temporarily thickening a layer of their epidermis, and producing
the appearance of darker skin in a localized area.
Humans who lived close to the
equator, with the highest level of exposure to solar radiation, were
found to adapt to this stress through the permanent darkening of skin's
pigmentation.
Finally, several cultural adaptations have developed from this environmental stress...for example:
Sunglasses 
Bathing Suits 
& Sunscreen 
The benefit of studying human
variation across various clines is that it removes prejudice or other
possible stereotypes from the equation, leaving only objective results
and expands our test group. It also allows us to see any potential
benefits of this environmental stress, such as vitamin D increases due
to exposure to solar radiation.
The use of race to understand human
variation, especially related to the study of solar radiation, would
just be a redundant restatement of the question. Skin color is simply a
more concentrated pigmentation due to these environmental factors. These
influences provide a static foundation for analysis across the variety
of humans, instead of promoting a changing test group...much more
accurate and objective.
Good explanation of the negative (and positive) impacts of solar radiation stress.
ReplyDeleteAdaptations are going to be positive process that help the body. Sunburns are indications that your body is NOT adapting fast enough to solar radiation and that damage is happening to your skin. Humans actually don't have a short term adaptation to solar radiation which is why it is such a dangerous stress.
Good discussions and explanations of the other three adaptations.
Yes, the adaptive approach takes race out of the picture and gives us more knowledge of human variation, but how can we use the knowledge we gain in a productive way? One example is the creation of sun screen to help our lack of short term adaptation to solar radiation.
While I understand your final point, it isn't an issue of "redundancy" but just that race, as a subjective social construct, cannot be used to understand biological traits. But you are definitely on the right track here with your thinking.
I always wondered why I would get very tan in the sun, then after a few hours away from the sun I'd notice my skin wasn't as dark as before. I now know that it's a facultative adaption to the sunlight. Very interesting post, keep up the good work.
ReplyDeleteI really liked your post! Not many people talked about the subject of solar radiation.
ReplyDeleteI think that it's interesting that people with darker skin are much less likely to burn versus people with lighter skin. I didn't know that burning was because our skin couldn't adapt fast enough to the heat.