Humans are clearly varied from one another, while all being the same is some other shape or form when it comes to how our bodies function. One of the most defining features about humans is how we are able to adapt to virtually anything given certain conditions, such as time to prepare, foresight one what to do, and a general idea of what to expect. Luckily, with the technology we have today, we are able to predict and prepare for situations we may have to adapt to, but even then there are times where even that's not possible.
Human variation is when we may not adapt as immediately and the only thing to their disposal is the traits they were born with.
Human Variation: Cold
The human body's internal temperature should always be around a high 35C to 37C, this is the body's homeostasis keeping the internal temperature at a specific level. In terms of a cold temperature, as the surroundings get colder, the body's hypothalamus will react and send a signal to the muscles to shiver in order to keep the body at homeostasis.
However, in the event that the surroundings are much too cold and the hypothalamus cannot regulate the body's temperature at homeostasis the decline in the internal body temperature will cause organs to fail as it slows down and in the end cause the body to die. This is the result of hypothermia, the condition when the internal body temperature drops too low causing the body to essentially freeze to death.
Short-term adaptation
Alarm Stage
GAS occurs when the body activates it's alarm system or it's flight-or-fight response. It reacts quickly to the stress by increasing your heart rate, activating adrenaline, releasing cortisol (stress hormones), and a sudden increase in energy in order to complete the task to get your body out of the area of stress.
Resistance Stage
As it begins to calm down and body has already reacted to the stressor, it slows down the processes of the Alarm stage called the Resistance stage. The amount of cortisol released is decreased, your heart rate slows down to a normal rate, but you mind and body continue to be alert until you are in safety. While in this stage, you may be more frustrated, irritable, and have a lack of concentration. When finally arriving at a safe state, your body's function normalize and you leave the Resistance stage.
Exhaustion Stage
In the case of a stressor not going away, and the body is in prolonged stress, it will continue to be in the resistance stage for too long and in this case the body will enter and exhausted state. Pro-longed Resistance will be followed up by the Exhaustion stage. Your body will be depleted of all it's resources that allow you to maintain a current healthy lively hood. You'll lose all strength physically, emotionally, and mentally. Exhaustion can cause multitudes of problems such and burnout, anxiety, and depression.
Facultative adaptation
Sun tanning
Sun tanning is an example of Facultative adaption in the case the phenotypic expression for one's melanin granules increase when exposed to high Ultra Violet Radiation exposure. UR Radiation is increased during the summer months, so this adaptation usually occurs during the summer and decreases in the winter months.
Prolonged exposure of the sun increases the size of melanin granules thus darkening the skin's complexion, and this can be done to those of any complexion despite it being more noticeable on those who are lighter in tone.
Though tanning is an adaptation to be able to withstand the UVR, some Europeans lost this ability and can no longer tan and they would have multiple sun burns over their skin and cause irritation in redness and peeling.
This faulty tanning is due to the lack of Mc1r, melanocortin-1 receptor, that produces melanin. Those without this protein cannot adapt easily to Ultra Violet Radiation and are at risk of skin cancer.
Because this adaptation is facultative, once UVR decreases in the winter months or the person stays indoors for long periods of time they will begin to lose their tan and their phenotypic expressions will return to "normal".
Developmental Adaptation
Developmental Adaptations are when there are changes in DNA in the overall population as a reaction to a stressor that is prolonged for generations, thus causing evolutionary changes.
Acclimatization
Upon entering high altitudes the body enters acclimatization, basically more red blood cells are produces so that more oxygen can be carried through the cardiovascular system. The lungs then increase in size and the intake and outtake of CO2, carbon dioxide, is also expedited.
The reason proper acclimatization is developmental adaptation is that there are those who are born to be better suited for living in higher altitudes than others. When these populations have been living in these areas for generations, their lungs increase in size and they also naturally produce more hemoglobin. Which allows for more oxygen to be carried by blood to allow them to live in higher altitudes.
An example of this are Tibetan Villagers who's phenotypic genes include 10 oxygen-processing genes that are not found generally in those who live in lower altitudes.
Cultural Adaptations
Cultural Adaptations are the literal adaptations of adopting different practices and cultures to enable them to survive in different environmental stressors.
Developmental Adjustment: Foot Binding
Though, not necessarily a positive adaptation, foot binding resulted in an adaptation in which a the anatomical change of Chinese women in the 20th century that developed in their life time into adulthood.
It was a popular culture practice to bind one's foot into tiny shoes in order to look petite, innocent, and cute and was considered to be attractive. So, the smaller the shoe the more appealing the women were to men at the time.
This cultural practice caused a Cultural Adaptation where the populations in this time all leaned towards wearing small petite clothing, more specifically shoes in order to "fit into the crowd" sort of speak, but this practice cause their feet to permanently shape into the shape of the shoes they wore when they were younger. Though it helped them attract men at the time it was none other than a stunt in normal foot growth as they grew older.
The practice involved binding the feet of young girls to stop the growth of their feet, and allow them to fit into small shoes. Even though this practice is no longer legal, and actually a form of mutilation now, at the time it helped these women gain higher statuses through marriage.
Benefits of Studying Human Variation
Studying human variation allows us, as humans, to be able to learn how we may learn about the factors that involve the adaptations and significance of why humans change and adapt in certain situations and stressors. This may include physical or genetic variation but either way know how humans will respond to certain areas of stress such as altitudes, sunlight, disease, and cultural practices.
With the study of these natural processes it may improve how scientists and doctors today treat different patients depending on the physiological and genetic variation involving human development. Such as skeletal adaptations where stressors such as physical trauma on the bones may vary depending on population that is effected. This study can be seen in Paleopathology, which covers this exact topic of trauma and diseases in the skeletal structure.
Race and Variations of Adaptations
Race in today's society doesn't really help us understand variation of human adaptations due to the melting pot of today's world especially in Western Society. Race wouldn't necessarily help us understand different adaptions due to race not necessarily equating to where one lives. However, it may help us understand this variations when consider their ancestors and or secluded populations today.
For example, when considering the developmental adaptation of the Native American Tibetan races. We can assume that because of their race and where they came from, their variation of race co-insides with their adaptation to high altitudes.
Good opening explanation of the negative impact of cold stress.
ReplyDeleteYou had some clear misconceptions on how this assignment was intended to be completed. There were explanations as to each type of adaptation presented in the guidelines and more information was available to you in your readings and in the Course Resource module under this specific assignment. Each of your examples is taken from other online sources and it created problems for you. I've reviewed what you offered here and made corrects, offering explanations and examples where necessary. Please take some time to re-visit the guidelines and the referenced resources before the final exam to make sure you understand these concepts.
Short term: General Adaptation Syndrome is a general pattern of response to any type of stress, not limited to environmental but often to psychological stress. This is too general for our purposes here and doesn't answer the question. We are looking for a specific physiological response to cold stress that helps address the problems you identify in your opening paragraph. An example of a short term adaptation to cold stress is shivering, which helps to generate body heat as a temporary fix for cold stress until facultative adaptations can kick in.
Facultative: Tanning is a facultative response, but your chosen stress here was cold stress, so what example of a facultative adaptation to cold stress can you offer? An example would be vasoconstriction, which helps to retain heat by preventing blood from going to the skin's surface.
You discuss "acclimatization" next in terms of adaptations to high altitude stress. "Acclimatization" is another term that describes facultative traits. Note that they are NOT considered developmental.
Developmental: You discuss foot binding as a "developmental" trait but this is a cultural practice, probably shaped by mating selection practices, and unrelated to environmental adaptations. A developmental adaptation for cold stress would be body shape, with shorter/compact body shapes being adaptive to cold stress, as explained by Bergmann and Allen's rules. An Inuit will be shorter and rounder, distributing that mass so that there is less surface area and also greater distance from the body core to the skin's surface. Both factors reduce the loss of body heat. Take some time to review those concepts.
Cultural: You don't identify a cultural adaptation to cold stress. An example would be warm clothing or shelters that help retain heat or even communal beds for retaining body warmth.
Okay on your next section. More generally, can knowledge on adaptations to cold climates have medical implications, such as redirecting blood flow to insured tissues? 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?
You start off the last section by correctly stating that you can't use race to understand human variation but that isn't because our races are so currently mixed. It's because of what race actually is. We need to start there first before we can explain why race is not useful in understanding human variation.
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.