Re: "The Blind Watchmaker"

From: Stevan Harnad (harnad@coglit.soton.ac.uk)
Date: Sun Nov 02 1997 - 19:44:12 GMT


> From: Nik Bollons <nsb195@soton.ac.uk>

> 1)Through reproduction, random mutations are ^—offered up^“
> into the population of a species.

Random mutations occur and are passed on if they improve (or do not
worsen) success at survival and reproduction. Another source of
variations on which selection can act is the recombination of genes that
occurs in sexual reproduction.

> 2)These mutations are not totally random but are under the
> confines of physics, and embryo development - otherwise
> evolution would have offered up things like ^—dragons^“ for
> selection.

Yes, the changes are small and gradual, operating on what was already
shaped by earlier evolution. I would guess that there is already so much
variety in the genome that evolution could probably accomplish a lot with
just recombination, which includes changes in the developmental
programme, which can often produce remarkable unexpected effects.

> 3)Also, mutations are usually in the direction of
> what existing matter the organism has already - stumps turn
> into fingers over a period time - rather than just creating
> something totally random.

Yes, once you get the ball rolling in one direction, it's easier to speed
it up than to try to get it going in another direction.

> 4)And, the mutation is never massive - such as a man with
> wings (macro-mutations).

Big mutations usually produce a "nonviable" foetus: a foetus that does
not survive to term. Our balance is too delicate to be suddenly shaken up
drastically and still survive to tell the tale.



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