Are there any similar cases between other closely related endotherms?
My default assumption would be that closely related species will have similar body temperatures. Checking a few sources, this is true of cattle and buffalo and sheep and goats. But as mentioned above, mammalian body temperatures are constrained within a small range, so many unrelated species have similar body temperatures.
Well, I can, because its all I’ve got. The depth of my analysis was limited to the time it took me to read the thread to that point (and being teleological I had started with the most recent post first).
Accepting Colibri’s list of other mammals living across a huge temperature gradient, then technological compensation can’t be seen as a pre-condition. And you’re right that it would have likely pre-dated the first expansion of humans out of Africa. Whether it makes a difference that the expansions are supposed to have taken place in more temperate climatic conditions, I don’t know. Both Neanderthal and Denisovan genetic differences are supposed to assist with their extreme environments, but whether these also predisposed then to managing the cold or different extremes as well is another question I don’t have an answer to.
The reason we learnt in school (it was biochemical engineering, so it was very little biology and sometimes totally wrong ) was to do with Lipids (fats) and proteins.
Above a certain temperature proteins get deactivated and below a certain temperature lipids in humans “solidify” (I think the technical term is unsaturate or saturate or something ). It was like a 5 F window in either direction.
Human adaptations to different temperature regimes have occurred, but they have tended to be anatomical rather than physiological. For example, Arctic peoples have thick bodies and relatively short arms and legs to minimize heat loss, while East Africans like the Masai are slender, tall, and have long arms and legs to shed heat.
We could run cooler and use different lipids though. (It was not unsaturate or saturate. Those matter for the melting temperature of lipids, but they don’t change in response to temperature.)
Our system for regulating body temperature evolved along with our other biochemistry.
I am not an expert and you maybe right there. We also learnt that colder climate plants produced oils which were low cholesterol (like olive oil) / lower melting points; whereas hotter climate plants made higher melting point oils like coconut oil.
Yes, that’s where the unsaturated (cold climate plants and seafood) vs. saturated (mammals and some tropical plants) comes in.
Not disputing you, but that leads to an interesting observation.
We’re warm-temp-compatible critters who it appears do better when fed a diet of cold-temp-compatible food. Eating the warm-temp stuff to excess clogs our plumbing right up.
Rather an unexpected result.
I don’t think the generality applies. The main saturated tropical oils are coconut and palm oils, which weren’t a part of our ancestral diet. And some tropical plants have unsaturated fats, like avocados. And of course, fish and mammals aren’t restricted to cold or warm environments.
The way I heard it, Fahrenheit used his wife rather than himself as the model for “normal body temperature of a human being”, sampled over a few days’ time. Apparently she had just ovulated and her temperature was slightly higher than normal as a result. Ha!
That was a (somewhat nerdy) HS Biology urban legend, though. How have we made it this far and not had this cited, or did I miss it while scanning the thread?
For lo!, The Master Spake Thusly: “In short, 100 means nothing at all on the Fahrenheit scale, 96 used to mean something but doesn’t anymore, and 0 is colder than it ever gets in Denmark. Brilliant.”
And although Celcius didn’t want his temperature scale named after him, he unfortunately promoted the term “Centigrade” (“scaled to 100”), which was abbreviated C, which everybody assumed stood for… Celcius. D’oh!
Maybe this is only relevant to where I went to school but C definitely stood for “Centigrade” there until the mid '70s.
I learned that Fahrenheit tried to scale temperatures from 0, as cold a temperature as he could create using salt and ice, and 100, human body temperature.
Same.
As with temperature, it has been suggested that the major benefit of skin color is the “side effect” of resistance to fungal infections (more important in tropical zones).
in temperate climates, our rate of thermogenesis changes each Spring and Fall. This explains why we can go out our shorts during those 40 degree F days of the January thaw. If we kept up that rate of thermal output in the summer, we’d all die of heat prostration.
The army is quite big in studying how to quickly achieve acclimatization. That involves changes in both thermal input and output. Being a sloppy system, that in turn implies steady state changes in body temperature.
Yes, Cecil was correct. 100F doesn’t mean anything. It was meant to.
0F was the coldest he could get with icewater and salt.
I find it fascinating that this happens despite our spending much of our time indoors, in climate controlled spaces.
Best way to heat acclimate quickly is to dig holes outside in the heat, then fill them in and repeat. sounds like the army, doesn’t it?
I’d not be surprisedif the long term lowering of avg. body temps was due to us spending more time inside, not doing hard physical labour.
The joke(?) I heard was that Fahrenheit was playing around with ice and salt to get the coldest possible temperature you could get by mixing the two. For the home scientist at the time, when nobody sold pre-marked thermometers, this was a logical step - how to make your own thermometer scale. The other end would be human body temperature. (So you didn’t have to mess around with an oven or open fire just to calibrate your thermometer) Then he took his temperature to complete the scale, but after monkeying around with cold temperatures for a while, he had a bit of a fever.
I assume that the answer is as mentioned above. There’s an upper limit and a lower limit at which our internal metabolic processes will work efficiently. The more consistent the temperature, the more efficient these processes can be. After eons of feedback tuning the result, the temperature regulation mechanism creates heat to keep us at the right temperature, and and the processes are tuned best for that temperature. If too cold, our body turns up the furnace, if too hot, we sweat and flush blood to nearer the skin, etc. Things like infections require the metabolic processes to go into overdrive, at which point the work they do produces extra heat.