<< At 08:31 AM 10/06/1999, George Murphy wrote:
> A question about theory rather than observation: How do we know that this
>increase in brain size happened "autocatalytically" -- a word he uses twice?
> (N.B. It's fine with me if it did - I'm as much of a fan of nonlinearity &
>nonequilibrium thermo as anyone. But does the word here mean anything
more than "we
>don't know the mechanism"?)
>
That is her view. But yes there is a feedback loop in place. In primitive
societies those who are smarter produce more offspring. Dumb people make
dumb mistakes and die. I think that is what she was referring to.
glenn
>>
Glenn,
You didn't answer George's question. You described the putative selection
process at comes after increase in brain size. Autocatalysis, however,
refers to the internal biological process that produces variability.
Let me try to answer George's question. Autocatalysis is the catalysis of a
reaction by one of its own products. That is, one of its own products acts
as a catalysis to the whole reaction. A catalyst, as students are told in
high-school chemistry, is usually a small amount of a substance that changes
the rate of a chemical reaction but that remains unchanged at the end of the
reaction.
So what is the product of increasing brain size that catalyzes the increase
in brain size? There is none that we know of. Applying "autocatalysis" to
increase in brain size shows that it is a metaphor drawn from chemistry for a
biological process about which we are ignorant.
As to your comment, Glenn, that "In primitive societies those who are smarter
produce more offspring"?--where are your data supporting that statement? You
know it doesn't exist. I agree that it is probably true that "Dumb people
make
dumb mistakes and die." That is the reason there are more offspring of
smarter people. It's not differential reproductive success; rather, it's
differential mortality.
Regards,
Bob