Re: Brains size and sweat

Wed 08 Jan 1997 14:00 CT

Bill Frix asks,
>>I would expect the 48 liters per 24 hour peirod represents extreme physical
activity in extreme temperatures. Is the data on the Oryx and Eland based on
maximum limits or average production?<<

In my calculations I used 12 hours of sweat for the human for the comparison.
The way the study reads is that the Elands and Oryx's were tested at hot, not
moderate conditions for the data I used. I felt that the hot represented the
best comparison, because moderate left too many questions in my mind.

I don't know about pigs, but so far I have not found an animal that has the
capacity to produce as much sweat as mankind. The book I got on camels says
they lose 8.8 liters/100kg on a hot day but that is still less than mankind.
(p. 67 The Camel, H. Gautiers-Pilters and A.I. Dagg, Univ. Chicago Press,

Bill wrote:
>>arguing for sweat glands being the result of increased brain capacity...<

This is not exactly what I am arguing for. The radiator theory of Brain
evolution would imply that until the body developed new ways to remove the
extra heaat from the brain, it was impossible for the brain to become bigger.
The solution for this was sweat gland first, brain size later.

Bill continues :

>>...this would place the greatest density in the scalp region<<<

As was so eloquently stated to me in one of my private discussions, the
cooling of the blood via sweat occurs mostly below the chin. However, that
said, the fact that the emissary vessels change direction and flow into the
head when we get hot makes for an additional amount of cooling. Animals like
the Eland,Camel etc are able to allow their body temperature to rise. Camel
body temperature can rise as much as 6-8 deg C. That is an 11-14 deg
fahrenheit temperaturerise. If you run that much of a fever, you will have br
ain damage. The Eland has a set of blood vessels that exchange heat in the
nose (if I recall correctly) to help cool the brain.

The difference in numbers of sweat glands among various populations that you
mention is not surprising. People who live in northern Europe have less need
to sweat than someone living at the equator. Also body shape varies along the
same latitudinal traverse. N. Europeans are broader and retain heat better.
People who live at the equator are tall and skinny. This helps get rid of
heat. A difference in the density of glands is not to be unexpected.