Big Brains

B Gilmour (
13 Jan 1997 18:44:49 GMT

I read an article a few years back from a theorist (cant remember his
name, I think he was Scandinavian) that said that large brains in humans
evolved as heat radiators. It essentially said that when humans made the
transition to the open savannas, heat dissipation became a major problem
(nakedness was one solution). Over 70% of body heat is dissipated through
the head. This was a result of mans mode of survival which required social
groups while hunting.
Man does not have the speed (due bipedalism) for quick kills like
predatory cats (which rely on high speed for short duration's, not
endurance). Their strategy would have been more like African wild dogs
which run down or track their prey over long periods of time and require
numerous individuals (social) to sustain the chase. While mans bipedalism
has restricted his speed, his endurance is unheard of in other mammals. Man
is the only mammal able to run marathons. Not even horses can sustain this
pace, heat dissipation (i.e. heat build up not dissipated in a smaller
brain) becomes a major problem which can seriously effect performance and
One can well wonder why we have this unique adaptation, and a large brain
with its associated capillaries, blood flow and subsequent ability to
radiate heat is an interesting concept.
Large brains are normally explained in traditional theories as an
adaptation evolved for speech (communication), binocular vision,
socialness, tool making, and others. But I suspect that a large brain could
have evolved for this more concrete reason, and the other traits are
exaptations that have found utility within the confines of a larger brain.
Extinction Events are the Evolutionary Pump for Diversity