Week 5 - Racism - Variation
In humans, maintaining a healthy
body temperature of about 98.6 is an example of homeostasis. This means that
the normal functions of the body that help to keep this body temperature and
the parts that help make it function as so will maintain an equilibrium. It is
important to understand that a healthy body temperature can also vary for
different reasons such as the metabolism, hormone levels, physical activity,
and sometimes the time of day can make the temperature fluctuate by as much as
one degree Fahrenheit. Elderly persons sometimes have a lower body core temperature.
If
an environmental stress such as a more extreme cold temperature is added, it will
negatively impact the survival of humans by disturbing homeostasis. In
temperature below 85 degrees Fahrenheit, the body would begin to cool rapidly
because it’s regulating system will fail and it would result in death from
hypothermia.
In extreme cold temperatures, the
human body would be affected in stages beginning with the exposure to the cold
temperature. The skin would give off signals to the hypothalamus which is sort
of the thermostat of the body and it serves as a way to control the body
temperature by triggering behavioral and physiological responses. The cold temperature
would begin either on the skin or spinal cord which would send signals to the
brain, or the brain would directly respond to the change in temperature. One body response is caused by the muscles by shivering
in a direct reaction to the cold temperature.
Goose bumps on the skin of a human arm with the hair raised.
Shivering is one short term
response in which the body would respond to the drop in temperature. It’s
caused by the effect the cold climate has on the muscles. What happens here is
a warming effect caused by the increased muscle activity. Another reaction is
goose bumps which is a reflex we have from our ancestors who had long hair.
When the temperature gets cold, the hair automatically stands up creating a
fluffy layer of warmth, but since humans no longer have much hair, what we see
are the goose bumps
on the skin.
An example of a facultative effect
would be the ability of the human body to reduce heat loss and to increase internal
heat production through a normal physiological response called
vasoconstriction. This is where the blood vessels near the skin surface narrow
preserving core body heat by reducing peripheral blood flow. The result is a
cooling of the skin and less heat is lost from the body. However, if the
temperature falls below freezing, continued vasoconstriction can result in
dangerous frostbite. The body then has another physiological response called
vasodilation. This is where the internal temperature regulating mechanism
responds by dilating the peripheral blood vessels thereby increasing the flow
of warm blood near the skin surface. The body alternates back and forth between
vasoconstriction and vasodilation to compensate for the risks of losing body
heat and frostbite. The balancing between both responses is known as the Lewis hunting phenomenon.
An example of developmental effect
would be the type of trait found in humans having more body mass when living in
extremely cold temperatures. Populations tend to be squat and round in colder
climates because the body fat and shorter height allows humans to retain heat
in their body core.
A cultural response to colder
temperatures is the use of insulating clothing, houses, and fires. In some societies humans have a tendency to
sleep in family groups with bodies close together to help minimize heat loss.
The benefits of studying human
variation from this perspective across environmental clines would be for
example understanding the effect of these additional types of biological responses to cold
conditions found among some human populations:
1) Increasing the basal
metabolic rate*
2) Fat insulation of vital
organs
3) Long term change in blood
flow patterns
By consuming large quantities of
high calorie fatty foods, the basal metabolic rate is significantly increased
resulting in the production of extra body heat. Eskimo’s in the far northern
regions and Indians of Tierra del Fuego a southern end practice this type of
diet as well as they remain active when outdoors to produce heat.
Ju/’hoansi of Southwestern Africa
and the Aborigines of Australia respond to extreme cold climate in a
differently. They develop a thick fat insulation around the vital organs of the
chest and abdomen as well as their skin cools due to vasoconstriction during
the night. This skin feels very cold during those hours, but the result is a
reduction of heat loss and the core body temperature stays normal. This
response the Aborigines and the Ju/’hoansi’s have would not be ideal if they
lived in constant freezing climate because the concentration of body heat in
their torsos would cause frostbite. Because they are hunters and gatherers, the
loss of their fingers would make it difficult for them to get food. This shows
how their physiological adaptation is to environments that do not normally
reach freezing temperatures for long periods. Their environments do not have a
lot of high calorie fatty foods either.
*Basal metabolic rate (BMR): the
measure of the total energy utilized by the body to maintain its necessary
processes while at rest. Those processes include keeping the heart, brain, and
other organs functioning normally and the necessary replacement of old or
damaged cells. About 75% of the food energy that we burn every day is used for
these functions. The remaining energy is used to fuel physical work or is
stored in fat reserves for when it is needed. Basal metabolic rate also refers
to the minimum level of heat produced by the body at rest.
Understanding how the environment,
how we adapt, and our biological reactions and and how our traits helps us better
understand the conditions our ancestors needed to adapt to in order to adjust, survive,
and develop the traits that have passed down to us today. It also helps us to
better understand why some humans can better adapt to extreme conditions and how these traits help us to better survive in extreme conditions such as
the colder climates.
Approving that race is not real, it’s
not reasonable to try to use race to understand the variation of the
adaptations listed here. The study of environmental influences on adaptations is
a more realistic way to understand human variation and our survival as it is a better
explanation of how the evolution of our related genetic differences between populations
of the world have helped us adapt and survive in our specific environments
given the various different environmental stresses and the traits inherited and
those we require to keep evolving and fit in our perpetually changing world.
Overall, good in your first section, but why can't the body function well below that optimal temperature? What happens to the circulatory system when the body temperature drops that makes it difficult for the body to function well?
ReplyDeleteVery good description on shivering and well done explaining the remnants of the adaptation seen now as goosebumps.
Excellent discussion of your facultative adaptation, including the discussion of the Hunting reaction.
Okay on your developmental adaptation but it isn't just more mass. It is the relationship between mass and shape that matters. You could have two people with the same mass, but one who is 4 feet and one who is six feet. The person who is 4 feet would be better adapted to cold climates because they actually have less surface area with their short, squat shape. This reduces heat loss and also places the body core deep in the body. The taller person would have more surface area and would more easily lose shape. That's why the long lean body shape is better for hot climates.
Good cultural adaptation.
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?
"Approving that race is not real..."
Let's clarify... race is not a real *biological* concept or trait. But unfortunately, from socio-cultural perspective, it is all too real. It is a system of organizing humans based upon their external phenotypes and every culture practices it in some form or another. This isn't making a judgment on the value of the concept of "race". But it the concept exists. The question here is, can we use race to better understand human variation?
"The study of environmental influences on adaptations is a more realistic way to understand human variation..."
Is "realistic" the right term? Or can we go further and state that it is *possible* to use environmental influence to understand human variation, compared to it being *not* possible to use race?
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.
I liked this a lot. I found it very interesting when you brought up goosebumps and how we usually get them when we are cold. Also, people take race very literally and in a conceptual sense it's very real. I also liked how you brought up vasoconstriction since I've never heard of it before and was quite eager to learn more about it after you brought it up.
ReplyDeleteI thought it was interesting to learn about goosebumps being a trait we inherited from our ancestors. I think you are very correct that people do take race literally and so it does make it real in a socio-cultural way as Professor Rodriquez pointed it out. I can't ignore that it does exist. Yes, our bodies are quite amazing the way vasoconstriction and vasodilation work in our body alternating back and forth to try to keep our body temperature normal and keep us from hypothermia and frostbite. Thank you for reading my blog!
DeleteLoved your post and thought it was well written and thought out. Your examples of the adaptations were easy to understand as well. Also, its good to know why I get goosebumps as well. Really enjoyed reading your blog.
ReplyDeleteI thought it was interesting to know why we get goosebumps. Knowing it's a reaction to keep us warm in cold temperature and that we inherit this from our ancestors is very cool.
DeleteYour post was very informational, I Honestly had no idea goosebumps were a way our body adapts. I learned a lot. Although I felt your last answer to race is not real needed to be assessed more in depth. Because in our social culture race is "real" We use not only in our everyday conversations but we also use it in our paperwork. When they ask us questions like what is your race on medical or school forms. It has become a "real" indicator in our social culture but in a sense yes you are right it isn't biological it not something you could necessarily test someones race in a sense.
ReplyDeleteI found the information on goosebumps very interesting as well. Thank you for the constructive criticism on race and how it is real in our socio-culture. I needed to think this through a little harder than I did before submitting it, but I do understand the concept is real. Thank you for reading my blog!
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