Human Variation & Race

Environmental stresses can make changes to the way we act in our lives. One environmental stress that can have a negative impact on our lives is cold. The body’s homeostasis is disturbed when an aspect of the internal environment goes outside of its normal limits. Cold temperature affects this in many ways. For example when we are cold, our body will constrict blood vessels to reduce heat loss. In extreme cases this can lead to loss of blood in the extremities of our body. This also leads to rising blood pressure, in response out kidneys will pull out excess fluid to reduce the pressure and which leads to urination many more times when it is cold. A full bladder is a place for extra heat loss, so urinating conserves heat yet this also causes a loss of fluids from the body.  

Humans have the habit of shivering when they are cold, which is a short term adaptation. When people shiver, muscles vibrate which heats the body.

A form of facultative adaptation is vasoconstriction, which is the narrowing of the blood vessels to reduce blood flow to the skin. It is an instinctive response to cold, and reduces heat loss from the skin’s surface. This can also be dangerous, because prolonged vasoconstriction can cause complete loss of blood to the extremities (hands and feet). 

A form of developmental adaptation is seen when looking at populations as a whole. People who live in cold environments tend to have shorter and rounder bodies. They are shorter because their hearts do not need to work as hard to pump blood to the hands and feet. These people are rounder/ heavier because their bodies gather fat around their vital organs to insulate the heat. Their bodies also resort to using this fat for energy.

 Two cultural adaptations are seen with clothing and food. People who live in countries where the temperature is extremely low have apparel which consists of think clothing made of fur or wool to maintain their warmth. They also eat foods with high fat and calorie content. This increases their basal metabolic rate, which in turn creates extra body  heat. During the cold weather, people slept in close huddles. 

Race can be used in different manners to understand the variations of adaptations. For example the cultural adaptations, can vary between different regions. Some people may resort to eating meats high in fat content where as other people may not eat meat but instead rely on other foods high in fat and protein. People's body shapes also make a difference. The woman pictured under developmental adaptation, shows the characteristics of living in an environment where people over time have grown shorter, and gain fat in different patters. Environmental influences is a better way to understand human variation rather that the use of race. This is because the environment reflects what happens with a persons body. A country has people of the same race, but each region of this country has different environmental pressures. One may be hot and another cold, affecting the physical appearance of the person and their diet. If we claim they are the same race so their variations will be the same, we are wrong.