Do humans acclimate to different climates?

Factual Questions
1

I have been thinking about how animals acclimate or acclimatize to different climates. For example, my horses grow heavy fur this time of year not because of falling temperatures but because of shortening daylight. Since I live in the northern hemisphere near the US/Canadian border my horses would have a heavy “winter” coat even if it was 80 degrees in December. This change serves them well since it can be -20 degrees F in the winter and having a thick coat keeps them warmer than they would otherwise. If I were to move them to the equator I assume they would no longer grow a heavy coat during the “winter” months.

I know that humans acclimate over time to higher altitude (and the subsequent drop in available oxygen) by increasing the number of red blood cells they produce. This makes sense since the more red blood cells you have the more oxygen you can transport around your body.

But what about temperature acclimation?

Do humans change in some physiological way to better tolerate colder or warmer temperatures than they are used to? For example, I was born in California and was rarely exposed to extreme temperatures (or humidities) when I was growing up. Three years ago I moved to NW Montana where the winters are long, cold and dry. It’s not unusual to be exposed to 0 degrees F or colder for weeks at a time during the winter months. Is my body changing in some way to make me more cold tolerant? I don’t live outside of course, but I am outside during the day and sometimes at night. It seems like I am better able to tolerate colder weather than when I was younger, but it may just seem that way.

So do people who move to different climates than they are accustomed to eventually acclimatize in some physical way? I know people who have moved from the western US to the southern US and say they never get used to the humidity in the summer there…

2

Really? Nobody knows the answer? I guess I need to dig deeper into this…

3

Well, thyroid function acclimatizes (adapts) to cold temperature. Example cite.

ETA: Or, take your pick.

4

There’s no physiological change that I’m aware of.

It’s pretty much all mental acclimation. For example, it’s 2 C outside right now, and it feels cold and crappy. When it’s 2 C at the end of February I’ll be barbequing in my Bermuda shorts and cartwheeling around the yard.

Not really, but you get the picture.

5

Opposite thing happening here. It was 32 F this morning when I went to work; but it didn’t “feel” like a cold, February 32 F day so I just put on a very light jacket. Would not even think of doing that in the real dreads of winter, let alone Bermuda shorts . . . :eek:

6

My point was that it will be - 20 to - 30 C here for months, so when it gets back to a balmy plus two I’ll be thrilled.

7

It seems clear from your question that you are ruling out phylogenetic adaptations of population groups; an area much-discussed, beginning with Bergmann’s Rule and later Allen’s Rule, in the mid-to-late 19th Century.

Regarding an existing individual’s acclimatization, this .edu link:

http://anthro.palomar.edu/adapt/adapt_2.htm

has some interesting things to note on your topic, including this:

“Most people have the ability to physiologically acclimatize to hot conditions over a period of days to weeks. The salt concentration of sweat progressively decreases while the volume of sweat increases. Urine volume also reduces. In addition, vasodilation of peripheral blood vessels causes flushing, or reddening, of the skin because more blood is close to the surface. That blood brings heat from the core body areas to the surface where it can be dissipated easily into the environment by radiation.”
That particular link also makes the following statements about adaptation under cold-climate conditions, stating that the following changes tend to take place:

  1. increased basal metabolic rate
  2. fat insulation of vital organs
  3. change in blood flow patterns

The article is unclear whether these changes can take place within an individual, or are simply part of the population group’s evolutionary response. However, the use of the term “adaptation” makes me tend to believe they mean solely the latter. Yet the passage on hot-climate acclimatization cited above notes many of the same strategies (in reverse) being available to the individual. Sorry for not being able to suss out whether this addresses your Q or not…

In any case, that page has some surprising strategies noted about harsh-climate strategies, including the adoption of calorie-rich diets to raise basal metabloic rates, and the vasoconstrictive physiological response exhibited (uniquely) by South African and Australian Aboriginals – both of whom do not live in consistently, but only seasonally-frigid environments – so full-body proportion changes as in Bergmann’s and Allen’s Rules, would turn out to in fact be poor adaptive responses.

8

Well, it might not be exactly what you were looking for, but there is also lighter skin pigmentation which allowed for greater absorbing of vitamin D in cold (and therefore less sun-lit) climates.

http://afp.google.com/article/ALeqM5jyOAlQsekPlvQmluyXlU1gL60iQw

quote from link :

Human migrations into new European and Asian environments created selective pressures favoring less skin pigmentation (so more sunlight could be absorbed through the skin to make Vitamin D), adaptation to cold weather and dietary changes.
One example of a genetic adaptation to human culture involves the gene that makes the milk-digesting enzyme lactase.
The gene normally stops activity about the time a person becomes a teenager, but northern Europeans developed a variation of the gene that allowed them to drink milk their whole lives – a relatively new adaptation that is directly tied to the introduction of domestic farming and use of milk as an agricultural product.

9

Quote from article:

Researchers in Germany recently showed that individuals from cold, dry climates, such as Greenland or Siberia, had higher and narrower nasal cavities than those from hot, humid climates, such as Papua New Guinea or Gabon. The German team, led by Marlijn Noback of Eberhard Karls University of Tübingen, took computer-aided measurements of the nasal cavities of 100 skulls representing 10 human groups living in five different climates. They found that the nasal cavities of cold, dry climate populations are relatively high and show a larger and more abrupt change in diameter in the upper part of the cavity than those of hot, humid climate populations. Her research was published online in the American Journal of Physical Anthropology this past June.

This narrowing of the nasal passage enhances contact between the air and the mucosal tissue, which helps to warm and humidify that air, Noback notes. Cold, dry climate populations also show a relatively longer nasal cavity, giving this population more space in which to bring incoming air in line with body temperature. Microscopic hairs called cilia, which line the nasal passage, help to keep out pathogens and dust that may infect or irritate the lungs, and the cilia work more efficiently when incoming air is moist. “Proper heating and humidification of air in colder climates are important for respiratory health,” says paleoanthropologist Nathan Holton of the University of Iowa. In warm-climate-adapted populations, inhalations are not directed toward the narrow upper part of the nasal cavity for warming. So “people from warm climates, moving into cold climates, could be more susceptible [to] colds and related diseases,” Noback says.

10

Tangent: I came across this while searching for the other stuff about human noses, because I thought I had read something about that at some point. If neanderthals (neandertals?) count as humans, some scientists thought their noses were cold weather adapted, although that is now in dispute
Also, it’s too late to edit it, but in my post #8 it should say “…in less sun-lit (and therefore cold)…”. I had it back-asswards, oops, sorry 'bout that.

11

If you’re talking fairly short-term (not ages and ages) for me, yes. We come from East TN where it can get pretty cold in the winter time. (10 below a few times.) Now we live on the Gulf of Mexico. I really don’t notice the humidity anymore, (when we first moved down here, every time I stepped out the door I felt like I’d been enveloped by a wet wool blanket) or the heat. (Some days are around 100 degrees.) As much as I sometimes get homesick, I’m not sure I could live back up there anymore. I don’t think my bones could take it. I used to think it was normal to get “bone-cold” and have my bones ache like I was 80 years old. But they don’t down here :smiley: and I like it.

12

I think they do. I see it almost every day; people who are new to Calgary are wearing a parka pulled up around their faces and gloves and a scarf, and the rest of us are running around in a light jacket. Some people never acclimatize to the cold here, but a lot do.

13

I think most people do. There are exceptions in which an individual cannot really acclimatize well over a lifetime. I’m thinking of people with immune systems that seem to be overactive and which don’t deal well in tropical climates (very light people), and very dark people who are more likely to have sickle-cell anemia and vitamin D deficiencies when in cold, dark climates.

But I think most of us in-between people do alright. Certainly there is obvious evolution of groups, skin color being the most obvious but other factors, such as short-legged mountain people (because they are sturdier), can also occur. These are very small changes compared to what we share in common which is–apropos-adaptability!

14

There are heat shock proteins whose purpose is to make the tissues of organisms including humans more resistant to heat. And I recall reading that there’s something similar for cold in an article mentioning this in conjunction with life in Antarctica; apparently the extreme cold causes so many resources to be diverted towards making “cold shock proteins” that it impairs mental functions by diverting resources from the brain. One of the researchers living there was quoted (from memory) as saying something like “Have you ever had one of these days when you just can’t get it together? It’s like that all the time.”

15

In my experiences of watching Canadian hockey players who have moved to Georgia, I would say yes. The first year these guys play here, they wear flipflops to the Christmas party and shorts year round. We had a pretty cold winter last season, and a player who’d been with us for 5 years or so came out bitching about the cold. Of course everyone - including the other players - laughed at him…

16

The Master Speaks.

17

My anecdotal input:

I was born in Florida and grew up all around the South. I lived in Kansas for two years and Colorado for one horrid winter, but beyond that I’d lived almost exclusively in the warmer parts of the southern US.

In 1997 I and my then-GF (who grew up in tropical Malaysia and considered Georgia winters “awful”) moved to Iowa, knowing basically nothing about it. When the first winter arrived, we had no idea what to do. We owned thin coats and some decorative sweaters, but that was it. When temperatures hit zero, we both freaked out; we were afraid to go outside, and got pretty miserable, feeling cooped up in the house all the time. Whenever we did go out, it would take literally hours of hot cocoa and blankets to get warm again.

After a few weeks of the cold temps, though, something changed. It was as though some internal thermostat switched our bodies into heat-production mode: All of a sudden we were able to deal with the cold just fine. We’d go run the dog in the big park near our house, trudging around in the snow for several hours, and our toes wouldn’t even get cold.

At the same time, both of our appetites went insane. We were both eating pretty much nonstop all the time, and not gaining weight. Apparently all the extra fuel we were taking in went entirely toward heat production.

Near the end of my second winter there, I went to run some errands one day. I remember the temperature outside was exactly 32 degrees, and I wore jeans, long johns, a t-shirt, and a sweatshirt. I was fine.

These days, in Memphis, if it’s 32 degrees out I’m wearing at least long pants, long johns, a t-shirt, a long-sleeve t-shirt, a flannel shirt or sweatshirt or sweater, and a heavy coat. And I’m probably cold anyway.

So: Yes, at least in my case it is possible for one person to adjust to a new climate. It was unpleasant and took a while for that dormant portion of my hypothalamus (or whatever) to wake up, but it happened.

P.S. Our dog, whose ancestors had been Southern for countless generations, didn’t fare so well. Once it got below about 5 degrees F, she’d get ice built up between her toes and didn’t have the instincts to deal with it. Several times I had to carry her 70-pound ass home.