Cold; An Environmental Stress
Long term responses to the cold can vary and long term exposure can not only be dangerous for humans, it can be fatal without adequate adaptation. An example of how too much exposure can negatively impact the survival of humans by disturbing homeostasis is when an individual develops Hypothermia; a life threatening drop of core body temperature to subnormal levels. Normally temperatures in humans are around 98.7 degrees (F) and while there are several factors, (e.g. metabolism, hormone levels, physical activity or depending on the time of day) that can cause temperatures to rise or decrease by a degree or so, hypothermia occurs when the core body temperature drops to 94 degrees (F). If adequate adaptation has not occurred the body temperature can continue to drop and failing to stay above 85 degrees (F) will cause the hypothalamus to fail, which will then in turn cause rapid cooling of the body. Likely resulting in death.
Short Term Adaptation
Our bodies have ways of rapidly responding to cold, and one way that we adapt in the short term is by shivering. Shivering is an involuntary response where we shake slightly and uncontrollably thus increasing internal heat production by generating body and muscle heat.
Facultative
Another way our bodies respond to cold is by way of a facultative response called Vasoconstriction. Vasoconstriction is a more energy efficient condition that rather than producing heat to combat the cold, it helps us to minimize heat loss. The process involves the narrowing of our blood vessels near the skins surface which preserves our core body heat by reducing peripheral blood flow. Provided that temperatures do not drop to the level of hypothermia, the skin will remain cool, which will in turn prevent heat loss at the body surface.Developmental
Two significant developmental factors that effect how we physiologically respond to the cold were addressed by a 19th Century naturalist named Carl Bergmann; aptly named Bergmann's Rule. According to Bergmann's Rule body size and shape are the defining factors in combatting the cold. For example, in animals, those that had greater mass and bulk to their make up were found to be in
colder climates. Larger body masses = more body heat being produced; the more cells they have resulting from a greater amount of heat. Larger animals tend to have smaller surface areas, which means there is less of an area to lose internal heat. An example of this in the animal kingdom is a Polar bear. Polar bears with their heavy fur and fat insulation along with their relatively smaller surface areas can retain their body heat.
Cultural
While there are less productive ways to culturally respond to cold, (e.g. drinking alcohol), I am going to focus on the following fundamental idea: insulated housing. When accessible, we humans have the ability to shelter ourselves in our homes, perhaps curled up in a blanket by a fire to keep warm. Cuddling up with loved ones can also help to minimize heat loss.
I believe the benefits to studying human variation from this perspective across environmental clines are that we are able to learn how our bodies can respond physiologically, whether it's by retaining heat or increasing heat production. Information obtained while studying this variation can he helpful in the future by knowing what factors will be needed when traveling to other destinations where the elements are far colder than what we're used to. Because we have now studied this type of variation and adaptations to this variation, we are now armed with the knowledge of what symptoms to look out for and to potentially be able to recognize dangerous developments or responses that might occur when exposed to colder climates. For example, I now know that when I am shivering it's my body's way of trying to help me by trying to produce body and muscle heat and that it isn't necessarily a red flag behavior.
Race as a classification alone should not be used to categorize humans, as we are not distinguished by characteristics or traits from one race to the next. Race was a concept that evolved to give reason to be able to deny rights and freedoms to some, while empowering others. Our genetic traits are inherited independently of each other and all humans have all evolved from our earlier ancestors. From a variation study point of view, race has no biological validity. The study of environmental influences on adaptations is a better way to understanding human variation because we can study the genetic make up of an individual as well as the environmental factors that may play a role in the variation type. Learning how those who came before us adapted or how those in colder climates adapt can lend to our being more prepared in the future. Studying how our bodies react to the cold in conjunction with our developmental and cultural responses is what gives us insight to human variation and our race has no bearing on those responses.



