Week 8 - Human Variation & Race Blog
1.
Too much exposure to high levels of solar
radiation can negatively impact the survival of humans by disturbing
homeostasis. For example, in the United States alone, 54,000 people are
diagnosed with the deadly skin cancer Melanoma. Furthermore, 8,000 of those
diagnosed die from this type of cancer. Being that Melanoma is one of the top
ten most common forms of cancer in the country, it is generally recommended
that everyone use some form of protection when being exposed to ultraviolet
rays. Normally, melanin in the skin acts as the protective agent against too
much sun exposure. However, too much time spend in the sun can ultimately alter
the DNA which leads to the development of Melanoma.
2.
Adaptations to high levels of solar radiation:
a.
Short-term adaptation: A short term adaptation
to exposure of high levels of UV rays is the reddening and peeling of skin
after sunburn occurs. It takes only 10 minutes of sun exposure to cause sun
burn. The reddening of the skin occurs as melanin works to defend the skin from
penetrating UV rays. Those with fairer skin might not be able to tan because
they have a defective form of skin protein called Mc1r (melanocortin-1
receptor). This skin protein, when normally produced, can help better protect
skin from the sun and produce a tan. The peeling happens as an after effect
from the melanin protecting the skin. In a day or two after the skin damage,
skin peels as a way to discard cells that might become cancerous, therefore protecting
the DNA from mutating. In less than a week, the skin should go back to normal.
b.
Facultative adaptation: Tanning is a facultative
adaptation that occurs readily in people with genes that let them produce more
melanin and help lessen sun burn occurrences. Tanning engages the melanocyte cells
in the skin to produce more melanin when exposed to the sun, therefore causing
a gradual change in skin color. After some time, the skin will return to its
natural color if there is less exposure to high levels of solar radiation.
c.
Developmental adaptations: People with darker skin
portray a developmental adaptation to high levels of solar radiation. Because
of the high occurance of melanin in the skin, those who live in areas of high
levels of sun exposure tend to have darker skin. This acts as a protective agent
against long exposure under the sun. This adaptation is genetically passed
through thousands of generations in order to increase survival of humans that
live in areas without much shade from the sun.
d.
Cultural adaptation: Clothes and headwear are some
examples of cultural adaptations to protect against high levels of solar
radiation. Those who live in areas or societies that spend a lot of time in the
sun tend to wear appropriate clothing to combat UV rays. It is essential for
many labor workers to wear appropriate clothing when working under the sun for
long hours every day. While styles differ around the world, head gear works the
same way; It protects the face, neck and shoulders of those working outside.
3.
One of the benefits that come as a result of
studying human variation across environmental clines is the knowledge acquired
in understanding how and why certain diseases or type of cancers occur. More
importantly, it guides scientists to develop solutions to combat these negative
impacts that occur due to environmental stresses. Understanding how different colored
skins react to short term and long term exposure to the sun helped scientist
understand why some people are more likely to develop melanoma and why others
are at more risk to develop Rickets disease. Ultimately, this information helps
scientist discover treatments and cures to combat these effects.
Good explanation of the dangers of solar radiation stress. Do we gain anything positive from exposure to the sun which complicates this issue?
ReplyDeleteFor your short term adaptation, remember that adaptations help the body adjust to a stress. It is a physiological response that has a positive impact. A sunburn isn't a positive response, it is an indicator that the body hasn't responded quickly enough to solar radiation. It is a symptom that damage has already occured, not a response to deal with the stress.
There actually is no short term adaptation to solar radiation which is why it is such a dangerous stress.
Good explanation of your facultative and cultural adaptation.
It isn't just dark skin that is an adaptation to solar radiation. All skin color is an adaptations, with lighter skin being adaptive in higher latitudes because less protection is needed against harmful rays but more production of Vitamin D is necessary. It is difficult for those with dark skin tone to produce enough Vitamin D in higher latitudes.
Good discussion of the medical benefits of this type of study.
" I’d say that black people are more protected against sun exposure than white people because of developmental adaptations"
Is that using race? Or is it using the adaptive approach and layering race over top of it? When addressing the question of whether you can use race to explain human variation, recognize that it is possible to answer this question with "no".
To answer this question, you first need to explore what race actually is. Race is not based in biology but is a social construct, based in beliefs and preconceptions, and used only to categorize humans into groups based upon external physical features, much like organizing a box of crayons by color. Race does not *cause* adaptations like environmental stress do, and without that causal relationship, you can't use race to explain adaptations. Race has no explanatory value over human variation.
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