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Article 2230 of comp.ai.philosophy:
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>From: harwood@umiacs.umd.edu (David Harwood)
Newsgroups: comp.ai.philosophy
Subject: Re: Scaled up slug brains
Message-ID: <45102@mimsy.umd.edu>
Date: 18 Dec 91 14:43:17 GMT
References: <349@idtg.UUCP> <45031@mimsy.umd.edu> <330@tdatirv.UUCP>
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In article <330@tdatirv.UUCP> sarima@tdatirv.UUCP (Stanley Friesen) writes:
>In article <45031@mimsy.umd.edu> harwood@umiacs.umd.edu (David Harwood) writes:
>|	As I said before, despite the neuron doctrine, I guess that the
>|neuro-morphogenesis of different species (and of individuals, for that
>|matter) is very specific, and sensitive to small genetic variation. 
>|(How many genes do slugs have anyway? They don't look like they have many.)
>
>They have aproximately the same number as we do.  All multicellular animals
>have DNA contents that are of the same order of magnitude.  The variation
>is at most about triple.  (Compared to ricketsias and viruses, this is
>totally insignificant).
>
>Brain structure, at least in forms with complex brains, tends to be *very*
>conservative.  The brains of the apes even have the same sulci as ours do,
>and *that* is just a topological feature to allow better packing!
>
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	Our President has a "brain structure" which "tends to be very
conservative" too.
	Virii? Do they have nervous systems?
	Same order of magnitude? Are we talking about the complexity
of a combinatorial system, eg involving the number of viable genetic
"programs"?
	This is entirely misleading. I've already pointed out 
(in another posting) that even small genetic variation makes for large
anatomical and physiological variation. Chimps may be 99+% like us,
but their brains do not have specialized language-processing areas,
and do not show related, major lateralization of function. A variation of
3/1 (?) in number of genes (what I asked) is immense in any case.



