Re: AAH: humans long-distance runners?

Gerold Firl (
6 Dec 1994 12:23:55 -0800

In article <3bo8bt$> (Clara N. Fitzgerald) writes:
> (Gerold Firl) writes:

>>Our cooling system is not optimally *efficient*, just extremely
>>*effective*. It rejects huge amounts of heat. A god, or an engineer, would
>>try to design a more efficient system; evolution just produces one that is

> Sweating seems to respond more to activity than internal temperature,
>hence the human tendency to heat stroke, etc.

No, sweating is triggered by the temperature of the blood, as sampled in
the brain. Specialised neurons, located in the middle of the brain, have
their firing frequency modulated by temperature. Sweating begins when these
neurons fire at a rate above the pre-set threshold level.

>>At 100 degrees fahrenheit a dog can cool its entire body by panting, if it
>>lays quietly in the shade to minimise the amount of metabolic heat
>>produced. A man can run at that temperature.

> As long as he has access to drinking water...

Right. Without lots and lots of water, we die. We are sort of aquatic that
way. Our cooling system appears to have evolved in an environment where day
time temperatures were high and water was plentiful. Where valuable
resources were availible to a species which could remain active when others
were incapacitated by heat.

Rift valley, anyone?

Disclaimer claims dat de claims claimed in dis are de claims of meself,
me, and me alone, so sue us god. I won't tell Bill & Dave if you won't.
=-=-=-=-=-=-=-=-=-=-=-=-=-=---- Gerold Firl @ ..hplabs!hp-sdd!geroldf