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Re: is our brain part of evolution?
Richard Ottolini (stgprao@sugarland.unocal.COM)
16 Oct 1996 13:22:39 GMT
In article <326455DA.3D06@megafauna.com>,
Stephen Barnard <steve@megafauna.com> wrote:
>Richard Ottolini wrote:
>>
>> One hypothesis is the large brain is a heat exchanger for the
>> demands of running. It brings lots of blood near the surface.
>> Kind of like a dog's nose.
>
>Very, very unlikely. The brain is an enormous consumer of energy. Head
>wounds are notorious for their copious bleeding, because the brain
>requires so much blood for nourishment. If you get overheated (playing
>tennis on a hot day, for example), an effective way of cooling yourself
>is to drape a wet towel over your head. This doesn't mean that the
>purpose of the brain is as an heat exchanger. It means that the heat
>that must be exchanged is disproportionately in the brain. It would be
>ridiculously easy to design better heat exchangers.
I was citing one of the more unusal explanations, not necessarily my opinion.
During evolution, often new functions arise from tissue that may have emerged
for some other reason. (That argument often comes up in explaining flight,
which has evolved independently at least a half dozen times.)
Adaption to bipedalism may have preceded most of the
brain function increases by 3-4 million years.
Anyone who has run ultra marathons or been outdoors in extreme elements
knows how equisitely sensitive the human head is as a thermoregulator.
A few inches of hat properly positioned can make quite a difference
in comfort or even survivability.
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