Re: running without salt & water

"Paul Crowley" <slkwuoiutiuytciuyik@xxxxxxxxxxxxxxxxx> wrote:

http://scienceblogs.com/bushwells/2007/01/marathon_runners_and_na_na_na.php

Yeah, but the marathon wasn't established until 1896 and so is of
little importance to human evolutionary history.

The point is (or ought to be) that sweating
causes the loss of body salts. Sweating
as a common response to exercise or heat
could only have evolved in a species
which was able to replace those lost salts
in a fast and convenient manner.

Ergo: humans evolved in a habitat close
to the sea.

Well, let's see if there are any empirical data to undermine that
hypothesis.
First of all, we know that those minerals are not restricted to marine
environments. Their availability varies from very high in marine
environments to low in tropical rainforest.
Second, there are the ethnographic data. We know that traditional
hunter-gatherer populations occupied a wide range of environments,
from seaside to rainforest. See for example:
http://www.ucpress.edu/books/pages/8940.html
They all must have found a way to replenish their electrolytes in
those different environments.

Sure, humans lose electrolytes through sweating, but not constantly in
a tempo comparable to that of marathon runners. That's why such
comparisons do not make much sense. Those are extremes. Under most
circumstances electrolyte loss is in a tempo that can easily be
replenished in a range of environments, even rainforest.
The only case somewhat comparable to a marathon is persistence hunting
under extreme environmental conditions, as observed in the central
Kalahari, see
http://www.journals.uchicago.edu/CA/journal/issues/v47n6/200064/brief/200064.abstract.html
And even under these circumstances electrolyte loss in acclimated
people is such that it has no detrimental effects and can be
replenished in a nonmarine environment.

There are no other hominid species extant,

Yep, and there's also only one extant aardvark species.

so it is to be presumed that they were
all competitive to humans or to human
ancestors. All must have occupied a
habitat close to the sea.

The competitive exclusion principle has previously been invoked to
explain such patterns, but was effectively declared dead in 1976 with
the evidence of contemporaneity and sympatry of Paranthropus and Homo
at Koobi Fora (Leakey, R. & Walker, A. (1976). Australopithecus, Homo
erectus, and the Single Species Hypothesis. Nature 261: 572-574.
O and btw, like so many other hominid sites, Koobi Fora is not close
to the sea.

Gerrit
.

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