Human Variation & Race

1. Select one of the following environmental stresses; Heat, high levels of solar radiation, cold, high altitude. Discuss specifically how this environment stress negatively impacts the survival of humans. 

Heat in humans, as well as some other species, such as horses sweat glands makes it possible to lose heat at the body at the body’s surface through evaporative cooling, a mechanism that has evolved to the greatest degree in humans. In fact, perspiration is the most important factor in heat dissipation in humans. However, there’s some variation, since people who aren’t generally exposed to hot conditions do experience a period of acclimatization that initially involves significantly increased perspiration rates. Heat reduction through evaporation can be expensive, and indeed dangerous in terms of water and sodium loss. For example, a person engaged in heavy work in high heat can lose up to 3 liters of water per hour. To appreciate the importance of this fact, consider that losing 1 liter of water is approximately equivalent to losing 1.5 percent of total body weight, and losing 10 percent of body weight can be life threatening. So, water must be continuously replaced during exercise in heat; also there are three substances that influence skin color: hemoglobin, the protein carotene, and most important, the pigment melanin.   

      2.     Identify 4 ways in which humans have adapted to this stress, choosing one

             adaptation from each of the different types of adaptations listed above (short term,

             facultative, developmental and cultural). Include images of adaptations.

         

             Heat  

      Humans drink plenty of water or fruit and vegetable juices. Avoid caffeine or alcohol.

      Humans limit their time outdoors, especially in the afternoon when the day is hottest.

      Humans limit exercise and/or strenuous activity.

      Humans watch for signs of heat exhaustion or heat stroke.

      Humans wear sunscreen

     Humans dress for the weather, they wear sun protective clothing, alternatively, loose-fitting, light-colored cotton clothes are cooler than dark colors or some synthetics

     Humans that live in a home without fans or air conditioning, open their windows to allow air flow, and keep shades, blinds or curtains drawn in the hottest part of the day or when the windows are in direct sunlight
     Humans may decide to spend at least part of the day in an air conditioned place like a shopping mall, a store, the library, a friend’s house, or the movies. Cool showers can help, too. Do not use a fan when the air temperature is above 95 degrees – it will blow hot air, which can add to heat stress.

                                     

Cold

Short -term responses to cold include increased metabolic rate and shivering, both of which generate body heat, at least for a short time. Cold be a negative factor because you can get frost-bite, it causes you to gain weight in the winter months because you are inside the house more which causes consume more food. The cold weather also cause high heating bills than in the summer.

High Levels of Solar Radiation

Melanin is a granular substance produced by cells called melanocytes, located in the outer layer of the skin. Melanin is extremely important because it acts as a built-in sunscreen by absorbing potentially dangerous ultraviolet (UV) rays that are present, but not visible, in sunlight. So melanin protects us from overexposure to UV radiation, which frequently caused genetic mutations in skin cells. These mutations can lead to skin cancer, which, if left untreated, can eventually spread to other organs and even result in death.

High Altitude

The rapid increase in hemoglobin production that occurs in people who live at lower elevations but travel to higher ones. An example would be if you spent a few days at a ski resort your tan would fade when exposure to sunlight is reduced, and hemoglobin  production drops to original levels after returning to lower elevations.

Physiological responses to environmental stressors are at least partially influenced by genetic factors, but some can also be affected by the duration and severity of the exposure, technological buffers (such as shelter or clothing), individual behavior, weight and overall body size.

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.

The benefits are as follows it shows us the diversity in our cultures just as no two people are alike. Environmentally, we live in different climates, some of us experience the four seasons; they wear thicker clothes in the winter and less clothes in the summer. There are some cultures that only experience cold weather and they have to bundle up wearing extra clothes. There are cultures that experience the warmer climate year round and they have to continually wear lighter clothing.  

4.   How would you use race to understand the variation of 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 variation would be the pigmentation of our skin. Exposure to sunlight triggers a protective mechanism in the form of tanning, the result of temporarily increased melanin production (acclimatization). This response occurs in all humans except albinos, who carry a genetic mutation that prevents their melanocytes from producing melanin. But even people who do produce melanin differ in their ability to tan. For instance, many people of northern European descent tend to have very fair skin, blue eyes, and light hair. Their cells produce small amounts of melanin, but when exposed to sunlight, they have almost no ability to increase production. And in all populations, women tend to tan as deeply as men. Natural selection has favored dark skin in areas closet to the equator, where the sun’s rays are most direct and where exposure to UV light is most intense and constant.