The cold is an environmental stress that disturbs the human
body’s homeostatic temperature. When the internal temperature is cold and off
balance, the body is more vulnerable to sickness due to less blood flow to
extremities, therefore, less white blood cells to fight disease. Disruptions to
the homeostatic temperature cause increases in blood pressure and impaired body
functions. This is because nerve cells as well as muscles function at a slower
rate in lower temperatures.
Humans, being the resourceful beings that we are, have
adapted to this stress in a variety of different ways.
A short term response is
shivering, the rapid contraction and release of muscles to generate heat.
A
facultative adaptation is a vasoconstriction, the narrowing of blood vessels to
reduce blood flow to the skin, therefore, reducing heat loss at the body’s surface.
A developmental adaptation is a subcutaneous fat layer that acts as insulation
for the body.
A cultural adaptation is a high carbohydrate, high fat diet.
Studying human variation across environmental clines like
this is beneficial because we can clearly see how the body is affected, for how
long, and at what level. Physiological responses to environmental factors are
controlled by genetics. Information from explorations like this can be useful
when looking at cases of extreme coldness. For example, we can look at a person
and be able to tell if they have been exposed to the cold for a long time or
not. If they are shivering, they have recently been exposed, and if they have a
layer of fat underneath the skin for body insulation, we might assume that they
live in a cold environment permanently, like the Inuits.
You can use race to understand variation of the adaptations
because it is commonly believed that cultural traits are associated with certain
physical traits. Also, people of the same racial group occasionally live in
similar environments and practice similar practices that might contribute to
the variation. It allows us to look at interactions between culture and biology
in adaptive characteristics. Studying
the effect environmental influences have on human variation is better than
looking at race because anthropologists have found that there is more variation
between different racial groups than within groups. Races are also the result of the human need to
simplify and organize complex ideas, and they are actually not very valuable to
evolutionary science.
For the most part, you cover a lot of the problems with cold stress. One caution, however.... actual cold stress will impede circulation. But that such a severe issue that your last concern would then be fighting off an illness. You would actually be close to death at that point. Getting sick is not the real problem there.
ReplyDeleteThere is an old wives tale that people tend to get sick in the winter because the cold makes it harder to fight off disease. That's false. We tend to get sicker in the winter because we ar forced indoors into closer quarters with other people, which increases the rate of transmission of disease.
Good explanation for your short term and facultative adaptations.
Be careful about increased fat layers as a developmental adaptation. Keep in mind that developmental traits are those you are born with, like skin color or lung capacity. So a developmental adaptation for cold stress would be a shorter, rounder body shape. This is described by Bergmann and Allen's rules (in the assignment sub-module), which explains that rounder body shapes reduce surface area on the body and help to trap heat in the body core. (Conversely, longer, leaner body shapes are adaptive to hot climates.) What you sound like you are describing the increasing body fat within a person's lifetime to adjust to a cold climate. That fits a facultative adaptation, not developmental.
Okay on cultural trait, but keep in mind that diet kind of straddles that strange middle place between culture and biology. Animals in cold climates also eat high fat diets... does that mean they have culture? Or is that just meeting their biological dietary needs?
Okay on your next section... but how does that help us? Let's think a little bigger here. How can we use the information we gain from this type of analysis that might benefit humanity in general? Can knowledge on adaptations to cold climates have medical implications? Help us develop clothing that retains heat more efficiently? Can we develop new means of home/building construction that might help increase heat retention? How can we actually use this information in an applied fashion?
Understand that race and culture are not same thing. Even if it was, three out of the four adaptations we are exploring here are biological, not cultural. So can we use race to understand these biological (or cultural) traits, as we are able to do with this clinal/environmental approach? It is important to recognize that the first step to exploring this issue is to ask 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.