Temperatures on Earth

[lifesagift]

But you're essentially correct: -50C and +50C are at the extreme limits of human endurance.

Boru

Human normal metabolic function adds heat and yet human body can not operate more the 2-3 degrees above its normal operating temperature of 37C. So human body must be able to shed heat. This become impossible when ambient temperature exceeds 40-45C on a sustained basis, so the human would die without mechanical cooling.

Likewise humans can only produce so much heat per hour and the speed with which humans lose heat increases with lowering ambient temperature. Without extensive thermal insulation humans would gradually suffer lowering body temperature and eventuaally die when ambient temperature drops below 0C.

So the real operating temperature range for humans without additional artificial insulation and cooling is more like 0-40C.

If you add artificial insulation and artificial cooling, the range expands dramatically. The best example is a space suit. A human in a space suit can survive -150C to 150C, sometimes both at the same time.

With great application of industrial resource it is conceivable humans can live on a sustained basis between -150C and 150C.

Plane and simple really... it's our normal body temperature that determines the conditions in which we operate best.

So that's begs another question.... why 37.2 deg C?

Wouldn't blood run quicker at 53.4 deg C, so making oxygen distribution much quicker, and hence humans much fitter, faster etc?