Human Variation and Race

Select only ONE of the following environmental stresses: (a) heat, (b) high levels of solar radiation, (c) cold, or (d) high altitude. Discuss specifically how this environmental stress negatively impacts the survival of humans by disturbing homeostasis. 

One environmental stress which negatively impacts the survival of humans by disturbing homeostasis is high levels of solar radiation. UV radiation is part of the electromagnetic spectrum that reaches the earth from the sun, with wavelengths that are invisible to the naked eye due to being shorter than visible light. These wavelengths are classified as UVA, UVB, and UVC. UVA radiation, which is the longest of the three wavelengths, is able to get through earth's natural ozone layer and affect humans by penetrating the epidermis and dermis layers of skin. UVB radiation is also able to get through the ozone layer, but only penetrates the epidermis layer of skin. UVC radiation usually is absorbed by the ozone layer, and has little effect on our skin. When we are overexposed to UVA and UVB radiation from being out in the sun for too long the result can be a suppression of the immune system. UVB rays are the more damaging of the two, and can potentially cause genetic damage that may lead to skin cancer due to it being directly absorbed by the DNA within cells. This damage that happens at the genetic level disturbs homeostasis, and can threaten the life of the human species. However, there is one benefit from the exposure to UV radiation that we get from being in the sun. This benefit is our bodies ability to stimulate vitamin D production caused by the UVB waves.

Identify 4 ways in which humans have adapted to this stress, choosing one specific adaptation from each of the different types of adaptations listed above (short term, facultative, developmental and cultural). Include images of the adaptations. 

Short term:

Unfortunately, humans have no short term adaptation to solar radiation. It is for this reason that solar radiation is an extremely dangerous thing for humans to be exposed to for extended periods without natural or artificial forms of protection.

Facultative:

One facultative adaptation that protects humans from harmful forms of UV radiation is tanning. When human skin is exposed to sunlight, a protective mechanism is triggered and the epidermis layer increases the amount of melanin that it produces. This increased production of melanin causes the skin to turn to a darker shade than it was prior to exposure, and this effect will remain until the exposure to the UV rays is reduced. One way that this is seen in humans is when during the summer months of the year, people spend more time outdoors in clothing that leaves their skin uncovered due to the hot temperatures. As a result, their skin will tan; assuming that they are genetically able to. Then, when the weather turns colder during the winter months, their skin will lose its tan complexion and return back to its normal shade as they spend less time outdoors and choose to wear more clothing.

Developmental:

Developmental adaptations to high levels of solar radiation are found in populations with high concentrations of people with dark skin tone. The darker a human's skin is, the higher the concentration of melanin that it produces. Populations that are exposed to the sun's harmful rays the most are located in arid, desert locations like Africa and some other tropical climates. This developmental trait is something that humans are born with, and it will not be changed over ones lifetime.






Cultural:

To make up for the fact that humans have no short term adaptations to high levels of solar radiation, we have come up with many cultural adaptations that we use regularly. Some of these include clothing, shelter, and sunblock. The use of clothing and shelter reduced our ancestors need to produce so much melanin. Also, migrating to areas that were more shaded such as forests allowed them to reduce the time that they spent under the stress of the suns UV radiation. This is why we can see a definite change in skin pigmentation between humans who occupy the northern regions and humans who occupy the southern regions near the equator. In modern times, the invention of sunscreen made it possible for people of all skin types to safely spend time in the sun without the use of clothing or shelter. Although, exposure to the sun's UV rays is still dangerous. Even with the use of sunscreen, which just limits the amount of UV radiation that your skin can absorb.  
















What are the benefits of studying human variation from this perspective across environmental clines? Can information from explorations like this be useful to help us in any way? Offer one example of how this information can be used in a productive way. 

The benefit of studying human variation in this way is that by studying the changes in various populations over a period of time, we can identify the environmental stresses that act on them. Information from explorations like this can most definitely help us. For example, if we study rickets, which is found in populations of lighter skinned people, we can further understand the importance of our need for sunlight and vitamin D.

How would you use race to understand the variation of the adaptations you listed in #2? Explain why the study of environmental influences on adaptations is a better way to understand human variation than by the use of race. 

Personally, I would use race in a way that makes it possible for us to see how our ancestors developed over time. To accomplish this, I would use race only to classify groups of people who inhabit the same geographical area that show the same adaptations to their environment. By doing this, it would also give us the benefit of understanding what changes will occur in a population of people who are exposed to the same environmental stresses.

In opposition to the use of race, studying environmental influences on adaptations is a better way to understand human variation because it gets people to see the ways that we as humans are alike, instead of the ways that we are not. I feel that this is a big factor in getting people to abandon racist ways of thinking. Studying the human species in this way can help us to understand that the differences we have between one another are simply responses to our environments; which are also very different. Our ability as humans to adapt and change to be better suited for our environments is something that connects us at a genetic level, and has nothing to do with being superior or inferior to one another.