I tried posting this to the “Comments on Cecil’s Columns” board, but nobody responded, so I’m hoping someone monitoring this board might have some insight.
I am trying to find cites for the claims put forth by Cecil in his coumn “Why do Eskimo people stay there?”. I have been talking to a med student about this, and she’s as incredulous as I am.
First, Cecil writes,
How, and by what? Admittedly, the blood passes through other parts of the body before reaching the heart again, but that is the case with all humans, so what kind of unusual mechanism do the Eskimo possess?.
Again, how? My friend says: “That’s not possible. By diffusion, or active transport, or what? And why not from the areolae?” It sounds fairly incredible – is there a medical name for this process? She also asks why lowering the temperature of the extremities would affect other organs.
Also, I’m wondering why reducing the temperature in the extremities is such a good thing – isn’t the idea to keep the extremities warm, not the other way around?
Coming from a Canadian who has been exposed to a bit of her country’s history: yes, people from Up North have some physiological adaptations to their environment, just as in other parts of the world where people have dark skin or small bodies or narrow eyes. But the other thing is that when Europeans came to Canada, they pushed the northern native peoples farther north than they would have preferred. A lot of those people would have previously lived a tad further south, or possibly even lived semi-nomadically at different camps during different times of the year to take advantage of seasonal food resources.
Blood is warmed in the arms by cross current methods. Think of it like this. You have the blood flowing to the hands, and the blood flowing back from the hands. Since the blood flowing to the hands starts off warm and then becomes colder, you have a gradient of heat with a max nearest the torso and the min at the fingers. So the blood coming back from the hand follows the same gradient because it runs alongside the blood going down. This is true of everybody, really.
You can also shunt blood from area to area by localized venoconstriction. Basically, your nervous system sends hormones to the blood vessels in the area and causes them to narrow so that blood flow is decreased. It can also do the opposite in areas that are important to survival (like organs and such) to cause the blood vessels to widen. Your own body does this in cases of hemmorhaging or when your blood pressure drops markedly.
You want to keep your organs warm because without those, you die. Without your fingers or arms, you’re inconvenienced (to put it lightly), but without your stomach or your heart, you’re gone right then.
Oops, I almost forgot to answer some of the questions. As to why this is unusual for Eskimos, I’d imagine it’s because they tend to have a stockier physique, with shorter arms and legs. This decreases the amount of heat escaping in their extremities. It’s not that other people don’t have these mechanisms, it’s just been more highly developed and utilized in people who are native to much colder climates.
Cecil’s column is a little misleading, then, if I read you correctly and the “blood returning from the hands is warmed” phenomenon and the “shunting blood” mechanism (which Cecil specifically attributes to “some northern people” – talk about being vague!) equally apply to non-Eskimo humans. If this is the case, the only differentiating features of Eskimo people are their “higher-than-ordinary basal metabolism rate” and the fact that they are “compactly built”.
I hadn’t actually read the column, so I’ll do it now. Ahh. Yeah, I suppose it is a little misleading. Although, as I am not a doctor, I can’t really say how much the shunting effect happens in response to cold in non-eskimo/colder climate people.
I’ve only ever heard of the characteristic stocky body type as an actual genetic adaptation to cold among Eskimos, less peripheral surface area, blood in the extremities for shorter duration, less cooling. IIRC, the higher than usual metabolism is mostly the result of diet, almost exclusively protein(or it was in the past). All humans can “shunt” blood away from the surface and toward their core when challenged with cold via vasoconstiction. I’d say Eskimo’s greatest adaptations to cold weather have been cultural, YMMV.
Very possible, but you could still suggest this is a case of short-term physiological adaptation to environmental conditions, similar to the Peruvian highlanders(and residents of Denver’s) tolerance for hypoxia, it may not be the case that a certain unique genotype exists, rather, exposure to the condition from birth effects development. I’m not aware of any evidence suggesting Eskimos have a unique genetic cardiovascular profile as compared to other extant human groups who evolved in warm or temperate climates. Interesting research topic perhaps.