Re: AAH: humans long-distance runners?
Pat Dooley (email@example.com)
Sun, 11 DEC 94 23:10:33 -0500
Phillip Bigelow <firstname.lastname@example.org> writes:
>However, your claim that "humans sweat way too much" is inaccurate. Humans
>sweat just the optimum amount to fit in to their environment. Evolution
>created the ubiquitous sweat glands on humans. The fact that humans sweat
>more freely than other mammals is evidence that they _need_ to sweat in
>order to function well. There is no compelling reason, as far as I can see,
>for an aquatic hominid to sweat as prodigiously as modern humans do. I do
>see a compelling reason to sweat buckets if you are scavenging in an open
>field in the hot sun all day long.
The optimum cooling effect of sweating is obtained when there is 100%
evaporation and 0% dripping. Humans are sub-optimal in this regard -
because their sweaing is too profuse they waste water. Worse still, they
have to drink more to make up for the losses. Go sweat buckets - you'll
suffer heat exhaustion long before you catch up to any savannah prey
unless you stay near water holes. You'll also lose salt and that's hard
to replenish on the savannah.
The AAH does not claim sweating as an aquatic adaptation. It notes
that, in common with many aquatic animals, humans lost most of
their true mammalian sweat glands. At the same time, the AA needed
a way to get rid of execess salt ingested with food and from aquatic
activity. Enter eccrine glands which, according to the AA, were
adapted for salt excretion. When the AA phase terminated, probably
because the Sea of Afar dried up, and the AA was forced into a more
terrestrial mode of existence, the salt excreting eccrine glands
became salt and water excreting glands - hence human sweating.