Anyone have any thoughts on a humanoid that had a low, perhaps even cold, internal body temp and how it might regulate that?

Also, would it make more sense to have said humanoids natively be from a cold world, or from a hot world? Initially I was thinking high ambient temps would cause the evolution of a lower internal temp to keep organs from boiling etc, but then was wondering if an overall cold temp could evolve something like this? Perhaps to help humanoids blend into cold ambient environment to evade heat seeing predators?



closed as too broad by L.Dutch, RonJohn, Bellerophon, Graham, sphennings Mar 15 '18 at 18:30

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  • $\begingroup$ How low of an internal temperature are you suggesting? (Note that cold-blooded creatures sun themselves explicitly so that they can get warm.) $\endgroup$ – RonJohn Mar 15 '18 at 13:48
  • $\begingroup$ Quick wikipedia check suggests penguins, seals, polar bears etc have body temperatures that are same or higher than humans. So it doesn't seem lowering body temperature would be useful adaptation to cold temperatures. Guess better insulation is very efficient solution? $\endgroup$ – Ville Niemi Mar 15 '18 at 13:58
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    $\begingroup$ Welcome to worldbuilding. Here we don't discuss ideas (what you call thoughts), we answer specific problems. $\endgroup$ – L.Dutch Mar 15 '18 at 15:12

The thing with "cold" is that it is relative.

If you mean homeothermic creatures, the most beautiful mammal is relatively cold when compared to us:

The platypus has an average body temperature of about 32 °C (90 °F) rather than the 37 °C (99 °F) typical of placental mammals. Research suggests this has been a gradual adaptation to harsh environmental conditions on the part of the small number of surviving monotreme species rather than a historical characteristic of monotremes.

All lifeforms evolve their thermal regulation - be it homeothermic or poikilotherm - to achieve primarily two goals:

  • To make sure they can stand whatever temperatures they might face on the environments where they live;
  • To be as much energy-efficient as they can be, given their lifestyle.

On the second point, for example: a crocodile can live on far less food than a lion of similar weight, since it does not use its own energy to keep its body temperature. However, the lion can afford to be relatively more active, and thus the extra energy cost of homeothermic regulation pays off due to its hunting style.

Now, back to being "cold". Imagine that, besides hominids, our world had also seen the rise of platypids, marvelous humanoid descendants of the amazing platypus. Should they keep their quadruped cousins' internal temperature, they would seem cold to the touch for us, even though they keep their temperature constant like all other mammals. Those godlike beings could manage to keep their temperature at a constant 32 °C (90 °F) by merely tuning their sodium pump leakage down.

If you want a less perfect humanoid that has a different temperature, do some reading on the last link above and taylor their thermal regulation mechanisms to your liking.

  • $\begingroup$ ok, yes the relative approach is a good one and as Alexander said below, there's limits for reducing internal body temp, at least using methods known to us atm. $\endgroup$ – Kalin Mar 15 '18 at 17:14
  • $\begingroup$ ok, yes the relative approach is a good one and as Alexander said below, there's limits for reducing internal body temp, at least using methods known to us atm. That brings the next question; what about the low environmental temp scenario? Like, say ambient temp of like -50 or lower. Could logic explain a species that, like a cold blooded creature here on earth, allow a constant low temp in a cold environment, but still remain warmblooded levels of active? Or perhaps a warm blooded creature that maintains a low body temp in order to blend in better with predators, or to conserve energy? $\endgroup$ – Kalin Mar 15 '18 at 17:42
  • $\begingroup$ Also, another question: How low is too low for a humanoid species, in theory? You mentioned that the platipoid species might maintain a 90F body temp, but humans maintain 98.6F so that's not really that far off from Human norm. What about maintaining a body temp in sub-32F ranges? Some sort of natural anti-freeze, perhaps high saline levels to reduce freezing? $\endgroup$ – Kalin Mar 15 '18 at 17:45


It is relatively easy to keep an organism warmer than the ambient temperature. It would be extremely hard to keep it colder (for an extended period of time).

Refrigeration technologies that are known to humans, like compression refrigeration and Peltier cooling would be extremely difficult to reproduce in a living organism (but you can try, of course). This leaves only evaporative cooling as an option, and Earth mammals are already using this technique, which is known as perspiration. Your organism can get good at that, but still, this technique has its limits and with ambient temperatures constantly higher than body temperature, it is virtually guaranteed that at some point that the organism will overheat.

P.S. If you desire not a constant-cold-blooded organism, but merely something colder than a human (but still warm-blooded), Renan's answer is a good one.

  • $\begingroup$ I bet you could refrigerate using chemical reactions, though ironically enough any refridgeration cycle would make the skin warmer to the touch. $\endgroup$ – Cort Ammon Mar 15 '18 at 17:15
  • $\begingroup$ That could be an interesting dichotomy .. But would be harder to explain how said species would evade heat seeing predators... They'd glow like a beacon... Hmmm... $\endgroup$ – Kalin Mar 15 '18 at 17:46
  • $\begingroup$ It might work if instead of skin you dumped the heat on exhaled air? I have been toying with the idea of a large flying lizard that would get rid of excess heat by using an internal heat pump to transfer it to a working fluid similar to sweat (more volatile chemicals might work better) and then injecting that in exhaled air. $\endgroup$ – Ville Niemi Mar 16 '18 at 0:16
  • $\begingroup$ @Ville Niemi for evaporative cooling, the cooling happens where evaporation actually occurs. If we have an internal organ for evaporation, then it becomes essentially a "live refrigerator". $\endgroup$ – Alexander Mar 16 '18 at 0:36

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