Re: Sweating is a dryland, not an aquatic adaptation in humans.
From: Paul Crowley (slkwuoiutiuytciuyik_at_slkjlskjoioue.com)
Date: 01/16/05
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Date: Sun, 16 Jan 2005 21:56:44 -0000
"Philip Deitiker" <Donevenask@worlnet.att.net> wrote in message
news:fN1Gd.20642$w62.17296@bgtnsc05-news.ops.worldnet.att.net...
> Animals migrate to where they can survive in competition with other
> animals. Humans live in the namib. very few other animals can live in
> the Namib, most of the animals that live in the namib have specific
> adaptations for living in the namib.
>
> Humans are one of the very few species of animals that can live and
> cross the sahara. The only other animals that can do this have
> specific desert adaptations.
While I rightly criticised Philip's post for its
early mistakes, there is much more that deserves
attention.
> Humans live in the australian outback most of which is desert. Most
> of the few species of animals that live in the outback have specific
> desert adaptations.
>
> Ego humans have adaptations for surviving in places where other non-
> desert animals cannot survive.
A crucial aspect of deserts (and semi-deserts)
for humans is that they have few large predators.
> What adaptations to the namib desert do humans have.
> 1. They sweat, in a dry highland climate with hot daily temperature
> sweating is a very effective way of keeping a heat producing brain
> cool.
The most effective way of keeping heat
down is to do little or nothing. Those
acclimatised to such conditions don't,
in fact, sweat much. They also have
remarkably small and thin bodies, and
sexual dimorphism is minimal. (I have
no figures on this. Does anyone?)
> Therefore hairlessness and sweating are desert adaptations.
Not true. No other desert animal follows
this pattern.
> Therefore the supply of water is
> not the problem with desert dwelling humans.
I doubt if they would agree. It's obviously
a (or THE) major limiting factor on where
they can live.
> Humans have adaptations.
> 1. They alter water usage over time to become more efficient water
> users in the desert environment. This reflects on some general
> physcially adaptive feature of humans that has been under desert
> selection in the past. Ergo part of the common evolutionary history
> of humans.
No 'ergo' follows. You might as well pick on
Inuit, and produce an 'ergo' based on them.
> 2. The learn desert plants and tubers that are reservoirs or water.
> 3. The learn to adapt gord fruits and eggs from birds, and skins as
> a means of carrying water.
> 4. They learn to travel in the morning and evening a and take
> shelter in the heat of the day, resting.
> 5. They learn to observe other desert animals, particular water
> sensing animals and learn where obscured sources of water are.
> 6. The learn to dig and reopen sources of ground water up and keep a
> collective memory of where these are so they cen reuse these in times
> of drought.
>
> Summary, humans can live in desert and semi arid climates (fact).
> The earliest branching of humans shows a people who are greatly
> adaptive to desert (fact)
It may well be the "earliest [known] branching".
That means next to nothing.
> other desert dwelling people around the
> world branched independently (deduced). Humans can adapt better than
> most generally adaptive animals to the desert (fact, exception being
> wolves, even so there are specific subspecies).
A silly point, since humans have techology.
> If you give humans the same amount of water, place one group in the
> desert with shade at one temperature, then place another group next
> to a swamp at the same temperature, as long as the desert living
> humans have adequate water they will be more comfortable than those
> living in the sweltering swamp.
Swamps are not healthy places for humans.
Semi-deserts MAY be better (in that respect)
but both are far from ideal as human habitats.
They are not places favoured for vacations.
It is perfectly clear that NEITHER was a
significant habitat during our evolution over
the past 5 Myr. (If either had been, we'd all
have distinct adaptations.)
> , sweating is ineffectual in a swamp, it is most wasteful in
> a swamp. It is the most effective adaptation in a desert.
The heavy sweating seen in north-European
adult males probably only evolved with north-
European adult males. The sweating of
ancestral human/hominid adult males would
have been limited by their access to fresh
water and to salt and was probably much less.
> It is an actual contradition. Sweating relies on the differential
> between the vapor pressure of water at a temperature and the vapor
> pressure of water at body surface temperature relative to the maximum
> vapor pressure of water (100% humidity). The closer the outside
> temperature is to body temperature, where the humidity is close to
> 100%, the efficacy of sweating drops. These conditions converge in
> equitorial swamps. The maximum rate of cooling by sweat is in a
> condition where the temperature is high but humidity is low, where
> the dry air can adsorb lots of water per unit of air. Breezey
> condition like on an arid plateau are best.
We can assume that most fighting between
human and hominid groups (and most
resulting fatalities) would have taken place
on territorial boundaries (as is the case with
chimps). Females and infants would stay
'in camp' at a low altitude near rivers and
lakes. Territorial boundaries would most
often be at higher altitudes.
Paul.
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