X-Message-Number: 3476
From:  (Thomas Donaldson)
Subject: CRYONICS: RE answer to Mr. Coetzee
Date: Mon, 12 Dec 1994 20:51:47 -0800 (PST)


Yes, insects and small creatures do have genetically determined nervous 
systems, some of which have even been mapped. However for creatures with large
brains, the consensus is that the structure of the brain (ie. its exact
connections) is NOT genetically determined. The reason is that there are so
many neurons that a great deal of the genome would have to be involved.

One sign that it is not is the close resemblance between the human genome and
that of chimpanzees. Furthermore, it is quite possible for brains to be
constructed without specifying connections in detail --- just approximately.

I did say CONSENSUS, however. We lack an actual proof or a detailed analysis 
giving evidence that genetic determination doesn't happen. The sources that
made this assertion did not cite any twin studies either, though they might
be found by someone who looks carefully (what you want is a map of the 
connections in small slices of brain taken from a pair of twins after their
deaths. Ideally you'd want more than one, and you'd have to be VERY careful
that the slices were taken from identical regions. Frankly I think this 
would be a good experiment to do, though you would only get much notice if 
you found out that the slices were identical. Otherwise everyone would 
just yawn).
			Long long life,

			   Thomas Donaldson
PS: Isn't it funny what a consensus does to people?

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