Tuesday, December 6, 2016
Human Variation & Race
The environmental stress I am going tone discussing today is high levels of solar radiation. This negatively impacts the survival of humans by disrupting homeostasis. One of main effects of this disruption at the hands of high solar radiation levels is skin cancer which can definitely reduce someone's chances of reproduction. Another, is a disruption in vitamin D development. A lack of vitamin D can affect bone growth and fetal development and thus affect someone's ability to reproduce. One way in which humans have attempted to adapt to this radiation, culturally, is through the development of sun screen that acts as another layer of protection against solar radiation. Facultative adaptations to high levels of radiation by humans can be found when humans tan themselves and purposefully expose themselves to UV rays in order to tan the skin. The tanning of the skin is caused by an increase in melanin production and thus people who are most susceptible to UV rays are better prepared to withstand it because of the increase in melanin. A developmental adaptation to this would be the evolution of people with naturally darker skin tones. Darker people are naturally less susceptible to the negative effects of solar radiation. However, darker skinned people do have a greater chance of having a vitamin d defficiency. I think there are many benefits to studying human variation from this persoective because it reinforces the fact that are phenotypic differences are not forms of superiority over one another but displays of adaptations to the various environments across the globe. You could use race to understand the developmental adaptation of darker skinned people as it literally pertains to the color of someone's skin. I also think race can be used to understand the facultative adaptation I mentioned as it is usually lighter folks who go to get tanned as darker people don't necessarily have the need to go and do that.
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Missing required images? And it would have been really helpful if this was broken into paragraphs. Difficult to parse out your answers.
ReplyDeleteGood discussion on the problems related to solar radiation stress.
I'm going to review your adaptations in the order presented in the guidelines.
Missing a short term adaptation? Humans actually don't have a short term adaptation to solar radiation (which is one reason why it is so dangerous) but this should have been noted here.
Okay on tanning as a facultative trait, but intentional tanning is not a natural biological process. It is the interaction of using culture to manipulate a biological facultative response. Just the production of additional melanin by the body in response to UV radiation alone is the specific facultative response.
"A developmental adaptation to this would be the evolution of people with naturally darker skin tones."
Correct, but the lighter skin tones is also a response to radiation stress, it is just a response to less radiation, which means we need less protection against skin damage but we also need more sun exposure to allow for Vitamin D production. All natural levels of basal melanin in our skin are developmental responses to solar radiation.
Darker skinned people are only in danger of Vitamin D deficiency if they move to northern latitudes.
Good cultural adaptation.
I agree that there are social benefits to having a better understanding of what actually causes our external phenotypic differences, but can you think of any concrete benefits? Can we develop new clothing or tools that help us deal with solar radiation stress, both the issue damage to our skin and Vitamin D production?
In your last section, are you actually "using" race to understand these issues? Does race really explain this variation?
Race is not a biological concept. It is a socio-cultural construct, created by humans solely for the purpose of categorizing and organizing humans by external phenotypes, and it is subject to our biases and preconceptions. Unlike the environment, race does not *cause* this variation. It only categorizes it. Without that causal relationship, you can't use race to explain human variation. Only the adaptive approach can do that.