Human Variation and Race

1.      Although I have lived in southern California my entire life and have experienced summers where temperatures can be in excess of 100F, I feel like I will never be used to the heat; However, earliest hominins evolved in the type of weather I have always lived in- mostly warm to hot woodlands and savannas of East Africa. Over time, hominins have evolved and adapted to heat to keep our bodies at optimal temperatures as to not do damage to our internal organs and our brains. The dangers of heat are very real. Just think about how many people suffer from heat stroke and severe dehydration during the summer or during sporting events. Heat can even cause death.

2.      One short term adaptation that humans have to negate the effects of heat on the body is perspiration or sweating. Humans have the ability to lose heat through the body’s surface through evaporative cooling – as humans sweat; the salt and water is evaporated from the surface of your skin draws heat away from the body. This is the most important way humans can cool down but sweating can also come at a cost. Sweating for prolonged amounts of time can greatly affect the composition of the body. During perspiration, humans lose both water and salt – both vital to life. Sweating can only be used efficiently for heat dissipation for a relatively short time before it actually becomes dangerous. For example, if a person is doing hard manual labor or intense exercise in extreme heat, it is possible to lose up to 1.5L of water and salt per hour through perspiration. For an average person, this is about 1.5% of total body weight and if a person loses 10% of body weight due to perspiration, the situation can become life threatening. 

                                          

A facultative adaptation that humans have to heat is vasodilation. Vasodilation is occurs when capillaries near the skin’s surface dilate to increase blood flow to the skin (This might cause a flushing effect when it occurs so skin looks red). Vasodilation essentially pulls heat from the center to the body to the skin so that it can radiate into the surrounding air, cooling the internal temperature of the person.

                                      

A developmental adaptation to heat is human body shape. People who live in warmer areas tend to be slimmer, and have elongated arms and legs so that the surface area of their skin is greater and can promote heat loss. The larger surface area of your skin, the more effective things like vasodilation will be in promoting heat loss.

                                           

A cultural adaptation to heat is air conditioning! Most people who live in warmer areas and extremely humid areas (in many first world countries) use air conditioning to control the climate within their homes and offices. When temperatures reach over 110 F in the summer, being able to escape the heat by going into an air conditioned building is a welcome rest for your body.

                                                

3.      The benefit of studying human variation from this perspective is that it really exemplifies how environment affects natural selection. Different races might have different skin colors or body shapes specifically as a result of adapting to their environment. This information would be helpful to us by showing us what climate we are adapted to and any precautions we might need to take to protect ourselves from the environment. For example, I am extremely pale and freckly with light eyes yet I live in an environment that is very ho and sunny. I need to wear sunscreen everyday to protect myself from skin damage and potentially cancer, whereas someone with darker skin might not need to worry about sunscreen or sun damage as much.

4.      I would use race strictly to outline a region where a group of people came from because their environment affected the adaptations that were needed for survival. I think in the current cultural and political climate, the best benefit to studying human variation from this perspective is that people might have a more enlightened view of other “races or ethnicities.” That “race” is not simply the color of someone’s skin, but that it has to do with variations and adaptations needed for survival and in that way, we are all the same. I think that some people perceive different races to be different “species.” People sometimes look at different races like they are comparing birds and fish. I think it would also be good starting point for understanding different cultures as well because adaptations does influence culture whether it has to do with food, dress, housing, lifestyle etc. It is all necessary for survival.