Environmental Pressures

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. (5 pts)

The human body performs at it’s most efficient when the it is in a state of homeostasis where a bodily function is occurring at the most desirable level. Thus, the human body is actively attempting to stay at that level and is performing normal corrections to its body systems to regulate itself back towards the desired state. Therefore, once various environmental pressures are introduced to the body it results in the body taking precautionary actions to try and maintain homeostasis. These natural protective mechanisms can be circumvented when the body is exposed to severe environmental pressures, such as when the body overheats due to extremely warm climates or serious bodily infection. In such cases, the body starts to slowly overheat as the core body temperature starts rising from the normal 98.6 F range and eventually results in the onset of hyperthermia around the temperature of 105-107 F as the body organs began to shutdown from excessive heat exposure. The body attempts to cool itself by sweating and reducing the core temperature, but these impacts are minimized in situations in which there is high humidity in the air for the sweat produced by the body cannot evaporate and cool the body. In dry, low humidity the body has no issue producing sweat to initially cool itself but the excessive sweating in a short timeframe results in the loss of water and vital salt nutrients that if not replaced can lead to the dehydration of the body. The body also attempts to adjust its salt concentration and urine volumes to account for prolonged heat exposure.

2. Using information in the assignment module, identify and explain four (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. (5 pts each/ 20 pts total)

Humans have adapted to environmental stress resulting from excessive heat exposure through a variety of different type of adaptations.

a.       Short term adaptation – The human body will start to sweat when exposed to excessive heat to cool the body and lower its core temperature back toward homeostasis. This involuntary body response alerts a person that their body temperature has increased and that they will need to find a way to cool themselves and replenish lost fluids.

b.       Facultative adaptation – The reddening of blood vessel due to vasodilation that occurs a person to become flush when suffering heat symptoms is an example of facultative adaptation. Heat is brought from core areas to the body surface and is expressed in the flush appearance that can be seen as people become acclimated to excessive heat

c.       Developmental adaptation – The Masai tribe in Africa is an example of a developmental adaptation that developed in a population over the course of generations in response to heat. The Masai are a very tall and slender people that possess very long arms and their body physique is perfectly suited to the warm temperatures that they live in. The slender body type is effective in warm conditions because it assist in that the long slender body has more surface area that is useful in the loss of body heat

d.       Cultural adaptation – People in excessive heat utilize hats, light clothing, fans and air conditioning, sunscreen, hydrating drinks and other cultural adaptations to help make themselves more comfortable in these types of living situations

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. (5 pts)

Studying human variation in this manner provides a better perspective why there are so many different variations of humans across the globe. This helps explain the variability of humans for it helps demonstrate how certain traits are developed to help people survive based on the environmental pressures that are unique to their environment. Thus, in many cases these traits are an expression of natural selection and provide humans with a greater opportunity to reproduce in that environment and whether physiological or cultural they are passed on from generation to generation to ensure the continued survival of a population. These explorations are helpful for they provide insight into what type of preparations need to be made to adjust to the environmental pressures of different locations or climates that one may be faced with while travelling to different sections of the world. For example, a light complexioned person travelling to the deserts of Africa know that they must bring proper protection from the extreme temperature in terms of protective clothing and sunscreen, since they recognize their lack of melanin does not provide them with sufficient protection from UV radiation.

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. (10 pts)

In study of race in relation to the heat adaptations mentioned above, one would look at the variations in race as populations were exposed to various levels of excessive heat exposure. By looking at race from this viewpoint one would understand the influence of environmental pressures on how certain areas were populated, and in terms of excess heat exposure there would most likely be a correlation between the complexion of the people that reside in such an area. Therefore, the discussion of the predominant group living in an area is not really a reflection of where a race has settled, but rather an expression of a group of people whose traits are most adaptable to thrive in a given environment. Hopefully, by examining in this manner people are able to understand that looking at race is not a good method at look at what differentiates people, but rather what we like to call race is merely an expression of environmental adaptations that are intended to help people thrive in their living situation. Thus, one expression is no better than another for we are all just expressions of the environments that our ancestors lived, so race is really nothing more complicated than that.

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