(November 26, 2014 at 4:58 pm)lifesagift Wrote: But that begs the question, why can most people only operate in a fifth of that range?
Define "operate". You won't be nearly as efficient at the extremes.
In extreme cold or heat, without proper protective clothing/shelter, you will die very quickly (literally within hours in the most extreme conditions). Even with proper protection from the weather, precautions have to be taken.