Baby, It's Cold Outside!

The environmental factor I will be discussing is cold.  I have chosen this because, having come from Chicago, I have a clear recollection of the bitter cold winters.  One frigid February day it actually got down to -27, with a wind chill of -70!  Even on the hottest days here in California, I have never felt anything like that.  To me, it seems like it would be hard for anything to survive (human or plant) for a prolonged period of time, in that kind of cold weather.   Every winter I would watch as everything in our garden died and all the trees became bare and the ground became cold and hard.  I think that is the epitome of a disruption of homeostasis.  I know you could argue that it happens here during hot spells but it seems like things are still alive.  I think the phrase “dead of winter” actually comes from the fact that everything is actually dead.

A short-term adaptation to cold is shivering, which I certainly did on that bitter cold February morning!  Shivering is the result of a constriction of the muscles in the body in an effort to produce heat to warm the body.  It is a natural response not unlike sweating.  Have you ever tried to “not” shiver when it is cold?  Pretty darn difficult!

A facultative adaptation, often seen in Eskimos and others who have lived for generations in cold climates in something called the hunter response to cold. The cycle of vasoconstriction and vasodilation in the extremities when exposed to cold is not unique – our bodies all do this.  The vasoconstriction is what helps our bodies retain heat, but unfortunately it restricts heat (blood flow) to our extremities) so at some point a dilation occurs in the extremities, and then the cycle repeats.  In people who have spent generations in cold climates, the amount of time between vasoconstriction and subsequent vasodilation is so small, as to appear almost continuous.  Their bodies have adapted this trait to survive in constant cold weather.

One developmental adaptation, again seen in the Eskimo population, which can be directly linked to the cold, is the shape of their faces.  The low brow and flat face has been linked to their need to eat frozen seal meat, a direct result of the cold climate, which over time, altered the shape of the face.

For cultural adaptations I am going to switch back to my personal experience because I think there are cultural differences between people who live in colder climates than people who live in warmer climates.  I know that when I was living in Chicago, and it was winter, we had a “hunker down” mentality and so we weren’t as social.  That changed with the seasons, but I would speculate that if a person lived in perpetual cold they would behave much like we did in the winter – they would socialize in tight circles and not spread out.  They would hunker down and stock up more (like hunt big game that might last longer).  We would do the modern times version of that by going to the big box stores and getting most of our groceries so we could avoid being out.  Our activities centered more on family.  Everyone also put on a little extra weight in the winter which we always attributed to being less active but now that I reflect, I wonder if it was also extra insulation and a seasonal slowing down of our metabolisms.  That is an interesting thought.  Everyone says California has a different lifestyle and type of “personality” than the Midwest and I agree, and I have to believe some of that comes from the cultural adaptations to weather.  I think the label that Midwesterners are more “down-home” may stem from the fact that they literally had to stay home due to weather conditions and it is a cultural adaptation.

I think one of the benefits to exploring human variation across environmental clines is that it is giving us another piece of the evolutionary picture that is critical to understanding our species in greater depth.  Take the sickle cell trait, for instance.  It turns out it was environmental all along – areas that had high rates of malaria were the regions where this trait was adapted.  This was an environmental impact but for a long time the trait was looked at only through a racial lens.  Once the lens was expanded it made it easier to conceive that this wasn’t a race-based trait, which was eventually confirmed. 

I think studying human variation from this environmental perspective is extremely beneficial because it takes away much of the stigma associated with race.  If discussions about the differences we see in humans are grounded in how they may have adapted to their environments it makes it more difficult to stigmatize people because of how they appear or even how they act.  For example, most of us have experienced cold weather at some time or another so if we were to consider the Eskimos behaviors and certain features as being the result of generations of adaptation to that environment they might not seem so different from anyone else.  At the end of the day, that is the most important thing – we are all the same, save for slight variations, and our environments play a big role in that.  One final thought - as I reflect upon what I wrote I realize that one of the best benefits is a greater understanding of society and how people interact with each other and how that is driven by environmental factors.  What I wrote about the differences between Midwesterners and Californians has just always been something I've heard people say and have observed, but after writing this, I now am curious about what might actually be going on, and if the environment is having a real impact on this.