Re: AAH: humans long-distance runners?
Phil Nicholls (firstname.lastname@example.org)
12 Dec 1994 05:10:01 GMT
In article <xCzU2XR.email@example.com>,
Pat Dooley <firstname.lastname@example.org> wrote:
>Phillip Bigelow <email@example.com> 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.
Pat, please try to remember that we are talking about EVOLUTION here
and not intelligent design. Evolution produces the best solutions to
problems of survival GIVEN THE CONSTRAINTS OF EXISTING MORPHOLOGY.
Sweeting cools the body. That is a fact. Forget the hunting
scenerios -- I don't think anyone today believes that early hominids
were hunters in a big way. More like opportunistic scavangers.
>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.
As I have pointed out several times, sweat cannot be a form of
salt excretion because sweat is hypotonic relative to body fluid.
If sweat were a salt excreting mechanism then sweat would be
hypertonic. That's basic chemistry. You also don't take into
consideration the fact that increased eccrine glands are a
Philip "Chris" Nicholls Department of Anthropology
Institute for Hydrohominoid Studies SUNY Albany
University of Ediacara firstname.lastname@example.org