Human Variation: Cold Weather
1.Colder weather affects homeostasis in humans by lowering internal body temperature past 94 degrees Fahrenheit which is called hypothermia. Since internal heat is not being produced quick enough the body may start to shiver or speed up the metabolic rate, both ways of increasing heat production. This is usually not as efficient because it requires the individual to increase their caloric intake. The other negative effect that the cold has on the body is through heat retention, not expulsion. Vasoconstriction reduces the blood flow near the body’s surface so the internal organs can retain enough heat to function. This can cause frostbite in the outer extremities of the body, in which the outer skin and tissue start to freeze and form ice crystals in the body. This limits the mobility of fingers and toes and in worst cases the tissue can die and those appendages need to be amputated.
2. Short-term adaptation: Shivering
Shivering is a short term response that the body goes through in response to cold weather , muscles undergo quick contractions and extensions in order to generate heat but this uses more energy than normal and is not intended as a solution to cold weather.
Facultative adaptation: The evolution of more compact bodies
The evolution of more compact bodies as a result of cold weather is brought up because of Bergmann and Allen’s Rules, which state that because the volume of an object increases faster than the surface area less heat is lost, the bigger the object is, and shorter, stockier frames contribute to less surface area respectively.
Developmental Condition: Basal Metabolic Rate
The basal metabolic rate of many people living in colder climates have risen due to the high caloric foods that they are exposed to, mainly meats and fats which increases the amount of body heat a person normally produces.
Cultural Adaptation: Fire
There are many cultural responses to cold weather like shelter, clothing made out of furs and fire. Sitting around a fire allows a person’s internal body temperature to increase without expending much energy.
3. There are a multitude of benefits of studying human variation across different environments. An important reason for doing so is seeing in what ways humans have adapted to their environment and how long it has taken them to do so. For example, the Tibetan people have lower amounts of red blood cells compared to the Quechua. This information can be used to see how climate change will affect some environmental clines moving into the future.
4. It is not possible to use race to understand the variation of adaptations listed above because they are products of the environment, not the people that live there over an extended course of time. Environmental influence plays a huge role on human variation in comparison to race. Humans must adapt to the environment or die out, that is how it is with every animal, the environment has also had an effect on human variation much longer than race has.
Good points in your opening section, but understand that what you are discussing here is the negative repercussions of the *adaptations* (shivering and vasoconstriction) not cold stress itself. The idea here is to explain why we need adaptations to cold stress in the first place. So what happens to the body when the core body temperature drops below the optimum temperature of 98.6 degrees? Why can't it function well below this temperature? What happens to our circulatory system and organs when the body temperature drops too low?
ReplyDeleteShort term: Good on the short term adaptation.
Facultative: Body shape is considered to be a developmental adaption, as explained by Bergmann & Allen's rules. Yes, we can become rounder by eating more but you can't become shorter/taller in response to cold or heat stress. An example of a facultative response to cold stress is vasodilation and also increasing the basal metabolic rate.
Developmental: BSM (basal metabolic rates) can and do vary from population to population depending upon the environment, but understand that your own BSM can change during your lifetime depending upon environment, diet and physical activity. The former qualifies as "developmental". The latter is "facultative". Make sure you understand the distinction.
Cultural: Good discussion here.
"This information can be used to see how climate change will affect some environmental clines moving into the future."
Okay... but what can we DO with this information in a way to help people? I agree that knowledge is always useful, but can you identify a way this knowledge can be useful in a concrete way? 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?
"It is not possible to use race to understand the variation of adaptations listed above because they are products of the environment, not the people that live there over an extended course of time."
I agree with the first part of that statement, but I'm confused about the last part. Some of these traits ARE the product of populations living in a given environment over an extended period of time. That defines developmental traits.
The reference to these adaptations being "products to the environment" is the key here. That refers to the fact that the environment effectively *causes* the adaptations to occur. There is a causal relationship between the environment and adaptations, which is why the environment has explanatory value over adaptations. Can the same be said about race? Does race have a causal relationship with adaptations?
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.