Heat as an environmental stress on a person negatively
impacts the survival of humans by disturbing homeostasis. It does so by making
it harder for the body to lose excess body heat. With the addition of high
humidity, it becomes even harder for the body to cool itself because the sweat
does not evaporate as quickly. Heat can cause heat strokes which can result in
death when severe enough.
A short term way humans have adapted to heat is by sweating. Sweating is the body’s way of releasing
excess heat to prevent the body from overheating.
A facultative way that humans have adapted to heat is by tanning. By tanning, a person's skin tone becomes temporarily darker making it so that the surface of the body absorbs more of the heat from the sun.
A developmental way that humans have adapted to heat is by hair loss. Humans have adapted to being less hairy in order to better regulate heat. We lack a lot of body hair that most other animals have.
A cultural way that humans have adapted to heat is by their
choice of clothing. When it’s hotter, people often choose to wear clothing such
as shorts and tank tops. They also choose to wear clothes that are lighter in
color and lighter in terms of material. People may also wear hats to shade
themselves from the heat from the sun.
Good opening description of heat stress and its negative impact on human homeostasis.
ReplyDeleteAccurate explanations on your short term and cultural adaptations.
Tanning may have secondary benefits for heat but it is primarily an adaptation to solar radiation stress. When you compare hot climates across solar radiation, skin color varies with variations with solar radiation, not with temperature. So what other facultative adaptation can you think of for adaptations to heat?
Loss of body hair in humans has been argued to be an adaptation to heat stress, but understand that this is one possible explanation and has many problems with it. For instance, if humans lost body hair early in their evolutionary history due to the heat on the African continent, why don't other animals have this same response? Also, body hair will actually help prevent damage from solar radiation, so why lose it? It has been suggested that loss of body hair may be the result of sexual selection. Lots of questions. Still working on the answers.
Missing discussions for the last two points on the usefulness of the adaptive approach and the problems of using race to understand human variation?
Good images.
Interesting post about heat. When I was younger and athletically fit, I was always told the more you sweat the more hydrated you are. Throughout your research was there any correlation between sweating and hydration?
ReplyDeleteIn regards to the section about body hair, I feel that could be classified as a cultural way humans deal with the heat/cosmetic. Because I think certain people shave body hair as a cosmetic feature, not so much as a developmental adaptation.
I've always found that it was interesting that sweat actually cools the body temperature. As each drop of sweat evaporates, it removes a tiny bit of heat with it. The wetness from the sweat also keeps the body cool because when the skin is wet, it feels cooler.
ReplyDeleteGreat post with great pictures. I did my post on the other side of this stress, so I wanted to read more about this stress to make sure I have a clear understanding. You did great at explaining.
ReplyDeleteIn the readings I found it interesting that some scientists believe that men are better at cooling off their body through sweating than women, though this still needs to be tested throughout the world. I wonder if women evolved to sweat less because it is not thought of as attractive. It reminds me when a friend in PE corrected me, "girls don't sweat, we glow!"