Human Variation

Human Variation

1. Homeostasis is a condition of stability within a biological system- so basically what you are experiencing reading this in your air-conditioned house and food in the pantry. However, the human lifestyle was not always this comfortable (and still is not for many people in developing countries) and because of this, we see a great amount of variation in our species.

Extreme temperatures disrupt our homeostasis and can prove lethal. But, through adaptation and acclimation, our earliest ancestors have managed to survive without modern day technology, and our younger ancestors to modern day humans also rely on technological (cultural) advances. One environmental stress that I am going to focus in on is the Cold.

The can kill even the strongest of people, and often in extreme conditions will lead to hypothermia- where the body’s temperature drops too low due to failure of the hypothalamus.  Cold weather can also lead to heart problems later on, due to the increased pumping of blood to try and prevent frostbite. Someone may also become ill due to the drier mucous membranes of the nose which can disrupt homeostasis and lead to death. Overall, even if one does not reach hyperthermia, but gets frostbite, the body will be disrupted and eventually, internal damage will pursue.

2. Humans have adapted to these less-than toasty cold conditions. There are multiple types of adaptation: short term, facultative, developmental, and cultural.

Short term: adaptations that do not require genetic change and only occur with stress.

Example of this in the cold:  Shivering

Shivering causes an increase in heat by the movement of muscles. Shivering occurs in short time periods and does not require extreme coldness to occur. Shivering does not require genetic change and only occurs when the body is directly faced with stress, which makes it a short-term adaptation that majority of modern-day human still experience on a chilly morning or evening.

Facultative: Genetic traits, turning off and on genes to alter phenotype.

Example of this in the Cold:  Vasoconstriction

the constriction of blood vessels, permitting decreased blood flow to the skin, which reduces heat loss and centers heat to the internal body. This probably could have been seen when early-modern humans living in the Northern hemisphere slept at night while the temperature dropped when they woke the next morning, the temperature would have increased, meaning that it would no longer be necessary or even vasodilation may have been necessary. The human body cycles between vasoconstriction and vasodilation to cope with the changing temperatures.

Developmental: Changes in DNA that are a result of long term stress. Only occur over generations, a type of evolution

Example of this in the Cold:  Fat storage and a bulkier build

If we take a look at our ancestors such as the H. Neanderthalis, we can see a trend towards bigger body size and higher body fat. Carl Bergman observed that smaller and thinner humans lived near to the equator and bigger ones lived in colder climates. This makes sense because the fat insulation of organs can keep the internal system functioning even in colder climates; whereas, if someone did not have this fat layer, they would fall to the cold much faster. This adaptation can be seen in other arctic animals such as polar bears- they store lots of blubber to store heat in the frigid temperatures.

Cultural: In short, human behavior and “technology”

Example of this in the Cold:  Mastering of fire, heater systems, and clothing- Human culture has helped as adapt to the cold for thousands of years, and evidence suggests the H. Erectus were able to control fire. Obviously, fire emits heat and can help keep someone warm. Today, in most modern countries, we use heating systems and generators to keep our homes warm, but many still use fireplaces and bonfires to keep hypothermia away. Also, we use warm and bulky clothing to trap our body heat and prevent the cold from getting in. We would not be able to last long in the arctic tundra without layers upon layers of clothing. Cultural advances have saved many lives and overall make temperatures more comfortable for us to live in.

3. Studying human variation has proven itself to be quite a task; however, scientists have used environmental clines to help pinpoint why certain variations exist. When looking at human variation as an adaption of people from different areas facing different environmental challenges, it becomes clearer how variation in humans has taken hold and why there is so much of it. Information from these explorations can be culturally helpful regarding racism. By helping people realize that skin color is one of many variations in humans and that the only reason people have variation in melanin is because of climatic adaptations, such as that darker skin protects more from the sun and lighter skin allows more absorption of vitamin D in cold climates, the world will be a much more accepting and less racist place. If everyone understood that skin color should be one of the last determinants of treatment, then we could make more progress in ending such unnecessary and unpleasant racism.  By understanding that variation is caused by rather than some bizarre and unfounded hierarchy system of races, we can actually understand why we are the way we are. The variation that we can see before our very eyes should be celebrated because humans are so adaptable and this level or variation is truly amazing.

4.  If we use race to understand the variation of adaptations listed about the cold, we would assume that all of these traits are associated strictly with Northern Europeans because they are lighter in tone (we know this is definitely not the case). To use race in the matter would be to assume that we mastered fire and cultural advances in heat because we are of a certain skin (once again, so very wrong). It would also be assumed that our ability to contract muscles to shiver and generate heat, as well as constricting our blood vessels is based off a phenotypic trait. At the end of the day, we would not really understand why these variations actually occurred and why there are so many variations but no subspecies of the H. Sapiens.

However, there is a way for us to understand human variation through adaptations to the climate. Using cold as an example, we can explore how the frigid weather acted as a catalyst in variation.  First of all, lighter skin was favored simply because of the climate in the Northern Hemisphere; Lighter skin tones produce a different amount of melanin and allow for easier absorption of vitamin D (which we can infer was scarce in the freezing climates). If we used race, it would help very little in understanding how adaptations led to variation; it would be like asking why leaves are green, and simply having the answer “because it's green”. That doesn’t make much sense does it? We know leafs are green because of the chlorophyll that assists in sun capturing and photosynthesis, so why leave it at the basic and useless explanation of a simply phenotypic expression? Clearly, we are not leafa, but studying from a racial perspective is the same thing. We can also understand that adaptations such as having a bulkier body were meant to keep us warmer and keep our organs insulated despite the less-than ideal temperatures. By using environmental influences on adaptations to understand human variation we can understand why we look different from a biological standpoint, rather than an outdated, and not to mention incorrect, racial view.