Human Variation and Race

1. 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 that negatively impacts the survival of humans is high levels of solar radiation. How so? Overexposure to UV radiation often causes genetic mutations with consideration to skin cells. According to the authors of Introduction to Physical Anthropology, “These mutations can lead to skin cancer, which, if left untreated, can eventually spread to other organs and even cause death” (Jurmain et al. 415). To avoid this disturbance in homeostasis, melanin, a substance produced by melanocytes, absorbs threatening ultraviolet rays. 

2. 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.

A short-term adaptation to a stress has much to do with an organism’s response to an environmental change in effort to maintain homeostasis. With high levels of solar radiation in mind, there is no short-term adaptation.

A facultative adaptation, on the other hand, requires an alteration of a phenotypic expression in response to the stress. A facultative adaptation to high levels of solar radiation is tanning. As discussed earlier melanin is essential in dodging dangerous UV rays. How do we acquire the production of melanin? Tanning, a form of acclimatization, provides a temporary increase in melanin production. The authors state that “most forms of acclimatization are temporary and last only until environmental conditions return to their former state” (Jurmain et al. 414). The act of tanning to produce melanin can be achieved by the majority of humans except for albinos. Albinos are unable to produce melanin because a genetic mutation prevents their melanocytes from doing so.

Developmental adaptations have to do with changes in DNA of a population, resulting in a phenotypic change brought on evolutionary forces. A developmental adaptation of high levels of solar radiation is dark skin. When discussing high levels of solar radiation, it is important to make note of folate, a B vitamin that must be replenished through diet. Unfortunately, ultraviolet radiation has been known to diminish folate levels in light skinned people. As a result, the authors mention the fact that “dark skin evolved rather rapidly as a protective response to the damaging effects of UV radiation on folate” (Jurmain et al. 417). 

Lastly, cultural adaptations are those in which humans use some form of culture to adapt to the stress, whether it be a clothing style or a tool. In this case, the use of animal skins in addition to sunblock provides a cultural adaption. Those who migrated into Asia and Europe wore animal skins or other types of clothing to protect themselves from the rays of the sun. Nowadays, UV protective clothing is available to purchase. Also, sunblock is often used to avoid a sunburn. Sunscreen bottles provide essential information such as SPF, or sun protection factor, which indicates how well the sunscreen protects an individual from burning ultraviolet rays (UVB).

3. 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. 

There is great benefit from examining human variation across environmental clines. By examining human variation in any given environment, we become aware of various conditions that may pose a threat. For instance, UV radiation is the most common cause of skin cancer. From an evolutionary perspective, we are reminded that early hominins lived in the tropical areas, spent most of their time outdoors, and did not wear protective clothing (Jurmain et al. 416). With this in mind, studies have indicated that these hominins, especially those with less pigmented skin, experienced lessened reproductive fitness. Also, we know that humans of northern European descent produce small amounts of melanin while those in the tropics remain deeply pigmented. By placing an individual with a specific set of traits in a new environment, new evidence arises.  

4. 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.

The use of race to understand the variation of adaptations is unnecessary.  The study of environmental influences on adaptations proves to be most effective. In this case, we examine skin color, a trait controlled by the production of melanin, across the environmental stress of solar radiation. Skin color serves as an adaptation through natural selection. The ways in which humans can successfully reproduce have to do with the adaptations previously mentioned. The tropics contain those with the most pigmentation while the northern latitudes hold individuals with lighter skin. As soon as individuals with dark skin migrated to the northern latitudes, the need for vitamin B immensely grew. Overall, we are enlightened on human variation by studying the expression of traits.

Citations

Jurmain, Robert, Lynn Kilgore, Wenda Trevathan, and Russell L. Ciochon. Introduction to Physical Anthropology. Belmont, CA: Wadsworth Cengage Learning, 2014. Print.