Comment by freddie_mercury

The temperature thing is one I always wonder about.

The WHO claims the ideal overnight temperature for sleeping is 18 degree (C). I lived in Vietnam for a decade and to a rough approximation 0% of the population ever experiences 18 degrees overnight for sleeping. And I imagine it's not too different in much of Thailand, Indonesia, India, etc.

I'm pretty dubious that hundreds of millions, maybe billions, are thriving in "suboptimal" overnight temperatures!

Does the African savanna regularly get down to 18c at night, such that we'd expect that to be some kind of evolutionary equilibrium that just happens to map to (northern) European and North American norms?