From: Ray Recchia (email@example.com)
Date: Fri 24 Oct 2003 - 10:29:42 GMT
At 09:05 AM 10/24/2003 +0100, Derek wrote:
> > One question is why we were the only mammal to go so
> > far?
>I used to wonder why, for example, there are no
>reptile lineages that have evolved larger brains -
>some did get as far as being bipedal and social. I
>vaguely remember that the answer was something to do
>with warm bloodedness, but I wonder if that argument
>still holds in the light of more recent ideas about
>warm bloodedness in dinosaurs?
>Is there a physiologist in the house?
I've read over and over that brains are very energy expensive to operate. I
think it is something like a ration of the brain being only 2% body weight
but consuming 20% of the calories. I can recall (but not find) an article
that hypothesized the calorie demands of a larger brain could not be met
until we became more carnivorous.
I think that the presumption has always been that tool use and greater
socialization required larger brains and that the fitness reward
compensated for the increased cost in calorie consumption.
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