Human Variation & Race Blog

1. Select only ONE of the following environmental stresses:  high levels of solar radiation Discuss specifically how this environmental stress negatively impacts the survival of humans by disturbing homeostasis.

Too much ultraviolet light can cause irreversible damage to DNA and important photosynthetic structures, while too much infrared light can cause overheating. DNA damage is caused by UV-B radiation. While most living cells have adapted and can repair simple damage, increased exposure to UV radiation can cause cells to mutate beyond repair, or to die. Overexposure to UVB radiation, which is directly absorbed by the DNA within cells, can potentially cause genetic damage leading to skin cancer, it is the more harmful of the two types of UV radiation.  This damage at the genetic level disturbs homeostasis and is life threatening to the species.

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 adaptation

Skin exposed to UV radiation can develop freckles and rashes. Short-term excessive exposure to UV radiation causes sunburn – reddening, pain and in severe cases blistering and even second degree burns.

Facultative adaptation

A facultative adaptation to protect us from the harmful UVB radiation waves is skin tanning.  Tanning happens when exposure to sunlight triggers a protective mechanism through increased melanin production in the epidermis layer.  Melanin is a natural sunscreen produced by our bodies and the tanning response will remain until the overexposure to UV rays is reduced.  As we spend more time in the sun during the summer months with the warmer weather, it is common to see people of both fair and dark skin have a darker complexion and then to have their complexion return to normal during winter months.  

Developmental adaptation

Nature has selected for people with darker skin in tropical latitudes, especially in nonforested regions, where ultraviolet radiation from the sun is usually the most intense.  Melanin acts as a protective biological shield against ultraviolet radiation.  By doing this, it helps to prevent sunburn damage that could result in DNA changes and, subsequently,several kinds of malignant skin cancers.

Cultural adaptation

As a result humans have used sun screen to avoid the amount of radiation that effect their skin. In order to protect skin from the sun people wear hats and try to avoid the amount of exposure. This in turn has caused a large amount of the population to be vitamin D deficient. 

3. In my opinion there is many benefits of studying human variation across environmental clines. By studying variation across environmental clines we learn how to adapt to the ever changing enviroment and the negative and positive affects that they have on us. They help find a solutions to some diseases and help us understand who gets affected and why.

4.  I would use race initially to understand the variation of the adaptations to try to see who would be more at risk of getting affected by high levels of solar radiation. The study of environmental influences on adaptation is a better way to understand human variation than the use of race. People of a certain race have many different traits within the same race. Race should not be the only thing considered.