Humans adapt day by day, as well as over many years and generations. These adaptations can be caused environmental stressors, that almost force these individuals to modify for survival. A specific stressor that has changed humans over time is heat. With an excess of heat in any given environment, species core temperatures can rise to an unbearable level, causing hyperthermia (core temperatures rising to about 105-107 degrees Fahrenheit). When this occurs, homeostasis within these organisms and their environment is disrupted and can lead to fatalities. In order to biologically protect themselves from heat, humans have adapted in a multitude of different ways:
- Short-term adaptation: a more obvious short-term adaptation to heat is evaporative cooling, the evaporation of sweat on the skin’s surface. Humans do this to overall, cool their body temperature while in direct heat or exercise.
- Facultative adaptation: skin tone is considered this type of adaptation due to the fact that lighter skin tones reflect the sun’s rays, while darker tones absorb it.
- Developmental adaptation: Bipedalism can be considered a developed adaptation. Humans ancestors were once quadrupeds but adapted over to this form of “transportation” to lessen the amount of surface area the sun contacted on their bodies when it was in it’s “heat peak”. This change also allowed the body to come into more contact with various breezes in the air.
- Cultural adaptation: A cultural adaptation could be air conditioners here in Southern California. They are common in almost all households in this region. And are used to keep internal temperatures low and comfortable. Though they are used, and affordable, all over the world, US culture has utilized and promoted their use for heat control for many years.
A benefit of studying heat on human variation across these environmental clines are extensive and essential in aiding mankind in dealing with this type of stressor. If we can understand how to manage heat related issues in different environments, people will be able to tolerate, or manage these different temperature climates. This allows people to create different technologies to aid us in this process and to benefit the quality of life in certain regions.
Race is not a sufficient tool in understanding these adaptations. Though it is easy to say that these difference “created” races, they are not direct indicators of that. Race can be indicated by a common language and cultural and historical connections. People from a multitude of regions have these different variations, body types, skin tones, etc., and do not come from the same “race”. These variations derived from different environmental stressors and cannot be “blamed” on race as a reason for their occurrence.
Good explanation of the negative impact of heat stress on the human body.
ReplyDeleteCorrect, sweating is a short term response to heat stress. Love the Steve Martin image!
Skin tone is an adaptive response to solar radiation. It may have secondary adaptive benefits to heat, but that is not the driving stress that shapes our skin color. An example of a facultative response to heat stress is vasodilation, which helps to disperse excess body heat.
Bipedalism is a possible adaptation to heat stress, but recognize that this is still very much up to debate. A more common example of a developmental adaptation to heat stress is the long lean body shape that helps to disperse heat from the body in agreement with Bergman & Allen's rules.
Good cultural adaptation.
Very good discussion on the concrete benefits of using information gained from the adaptive approach to human variation.
"These variations derived from different environmental stressors and cannot be “blamed” on race as a reason for their occurrence. "
I wouldn't use the word "blame", but you have the right idea here. This is a difficult concept to explain, mainly because people usually don't really think about what race actually is. Race is a social construct, subject to bias and interpretation, based upon external phenotypes. The key here is that in order to use one factor (i.e., such as the environment) to explain another (adaptations) you need to have a causal relationship between the two. We see that with the environment, which causes our adaptations to appear. Does race have that causal relationship as well? No, it doesn't. Race doesn't cause adaptations. In a sense, adaptations "cause" race, since they are used as the basis to define race. Without that causal relationship, race is useless in explaining human variation.
Hi there! I was sort of confused by the statement "lighter skin tones reflect the sun's rays" because I think they actually are more absorbent and more easily damaged than darker skin! My blog post was about skin coloring, and how humans produce more pigment in the skin when they are exposed to more UV rays (sunlight) so that their skin can absorb those rays without damaging the underlying epidermis (skin cells). I really liked your images!
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