Human Variation & Race Blog

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.

The disruption of homeostasis can occur with high levels of solar radiation which is an environmental stressor. The reason High levels of solar radiation negatively impact the survival of humans is due to the fact that while UVB radiation penetrates through the epidermis layer, UVA radiation has the ability to go beyond the epidermis and penetrate straight through to the dermis layer. Although UV radiation does provide stimulation of vitamin D production through UVB waves which is beneficial to humans, overexposure of UVB and UVA rays can still cause dangerous sunburns and short-term suppression of immune systems. This type of UVB exposure becomes directly absorbed by the DNA within cells, and this absorption has the dangerous potential to cause genetic damage that could lead to skin cancer. Any genetic level damage directly disturbs homeostasis and is potentially life threatening to humans.

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: Humans have adapted to exposure to the sun in appropriate and measured timeframes that are unrelated to vitamin D production. Short term adaptations consist of enhancing mood and energy through the release of endorphins, melatonin regulation through the "third eye" of the pineal gland photoreceptors, regulating body temperature, UV radiation also enhances skin barrier functions and helps in treating skin diseases, such as psoriasis, vitiligo, atopic dermatitis, and scleroderma.

FACULTATIVE:  the process of developing facultative pigmentation is better known as cosmetic tanning. Facultative Pigmentation is the level of an acquired tan developed by an individual exposed to ultraviolet light. It protects us from the harmful UVB radiation waves is skin tanning.  The process of tanning occurs when exposure to sunlight activates a protective mechanism through increased melanin production in the epidermis layer.  Melanin is our body’s naturally produced sunscreen and the degree of tanning will take place until the overexposure to UV rays is reduced. 

DEVELOPMENTAL: You can see developmental changes in populations that have a higher concentration of people with darker skin.  Higher concentrations of melanin are found in individuals with dark skin which acts as a natural sunscreen that a person’s body produces.  Populations that are more exposed to the sun’s harmful rays reside in mostly in African and Tropical climates.  In this regard, geographical locations makes a difference in the number of people with darker skin however, those with darker pigmentation can tan and sunburn as well. Regardless, of where one lives, it is evident that too much exposure to solar radiation can result in skin cancer and not enough exposure can result in a Vitamin D deficiency which results in the inability to process calcium and also weakens bones.  Populations that reside in locations with limited sunlight can suffer adverse effects such as developing diseases like rickets, which is when bones are too weak and can’t support the weight of the body as it grows. 

CULTURAL: Cultural adaptations to protect a person’s body from harmful UVA /UVB rays has occurred through clothing, adequate shelter and with the development of sunscreen. Clothing and shelter gave humans the ability to protect themselves from direct exposure and in turn resulted in the reduced levels of melanin production. Even by migrating to environments that helped protect from harsh UVA/UVB elements such as forested areas also helped to reduce sun exposure.  Throughout history it is evident that skin pigmentation has become lighter in various populations more specifically northern geographical regions and darker skinned populations are more concentrated  in southern regions that are closest to the equator.

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.

By studying the vicissitudes of diverse sample populations over time, this enables us to assess and see how environmental stressors affect various populations.  One example would be studying the high rate of sickle cell anemia in black populations. This type of research can help scientists identify and develop treatments to hopefully cure or just help other people diagnosed with sickle cell anemia and not just limit it to one population.  Also, studying the cause and effect of rickets in populations with fair skinned people can help with the understanding of the need for sunlight and how much of it is actually necessary to avoid the certain diseases.

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.

I believe that studying diverse races is an important aspect of understanding variations of adaptations. I think race tells us quite a bit and although it won’t answer all the questions, it would certainly give us great insight. However, going by race alone would be rather myopic and would have many limitations in regards to the information that we would be looking for. Therefore, studying environmental influences of vast populations as a whole would be more telling as to how outside stressors have influenced adaptations in humans overall.