Re: Brains size and sweat

William T. Yates (
Thu, 09 Jan 1997 16:59:10 +0000

Glenn Morton wrote:
> >I've been working up a sweat trying to follow this discussion, and I
> >think my brain is overheating!
> >
> >A question: Man may sweat profusely, but isn't the cooling effect
> >dependent on how much of this water is actually evaporated from the
> >skin? That's the way the heat energy is removed, by using it to
> >dissociate the liquid water molecules into water vapor. Agreed, the more
> >you sweat, the more water is available for evaporation, but I wonder, is
> >there an optimum rate for sweating where you achieve the maximum cooling
> >effect with the minimum loss of bodiy water? The point being that merely
> >the rate of sweat production is not the whole story in the cooling
> >effect. Much sweat simply drops off.
> >
> You are correct. However, the Savanna, where man is believed to have evolved
> is relatively dry. When you work in a dry region much more of the sweat
> evaporates quickly and less drops off. When I have worked outdoors in the
> western US I ususally don't drip with sweat. But when I lived in Louisiana, I
> would drip sweat simply sitting on my back porch reading.
> >And re the Watusi... don't forget the Pygmies! Africans come in varied
> >body styles!
> >
> Pygmies live in an entirely different climate than the Watusi's. Chris Ruff
> writes:
> "It is interesting and instructive that all present-day populations
> exhibiting the extreme linearity of body build illustrated by the Nilotic in
> Figure 1 inhabit not only hot environments, but also relatively open, dry
> environments, such as savannah grasslands. As Wheeler has demonstrated
> theoretically, a tall linear body is a distinct advantage when moving about in
> the open during the day. Relative to its mass, such a body leads to less heat
> gain from the sun, particularly near mid-day, and greater convective heat loss
> from the body, particularly in the morning and late afternoon. In contrast,
> in a closed, forested environment with little direct sunlight and little air
> movement, this kind of physique loses these advantages. In addition, the
> usefulness of a relatively large surface area for evaporative cooling by
> sweating is decreased in a humid environment. Thus, given the fact that heat
> production is related to body size, the best way to avoid overheating under
> such conditions may be to limit body size itself. This is one interpretation
> of why present-day Pygmies, whether in Africa or elsewhere are universally
> found in rainforest environments."~Christopher B. Ruff, "Climatic Adaptation
> and Hominid Evolution: The Thermoregulatory Imperative," Evolutionary
> Anthropology, 2:2 (1993), p. 53-60, p. 56
> "In hot, wet climates. like rain forests, sweating is less effective.
> People adapted to those environments often have the same body width as those
> in hot, dry areas but are short, like Pygmies, to keep their body mass
> low."
> Are you the guy who bought a book from me in early 1994? If so I think you
> have the first copy out there.
> >Just wondering...
> >--Bill Yates
> glenn
> Foundation,Fall and Flood
You've got answers for everything, don't you! :) I enjoy your posts!
Afraid I'm not the guy. I'll think about buying one, though!

--Bill Yates --