Re: Not enough info for your brain (was Re: Dawkins video)

Greg Billock (
Tue, 16 Jun 1998 08:47:35 -0700 (PDT)

Glenn Morton:


> >mutation causes an information loss) studied signal/noise relationships in
> >DNA as a Johns Hopkins fellow, and has published on the subject in the
> >Journal of Theoretical and Mathematical biology.
> Why is there no reference with this? No one can check him out if he
> doesn't give references. It always gets me when people make statements that
> can't be verified, like this above.

Evidently JTMB split a dozen years ago or so. Now there are JTB and JMB,
and Spetner has no publications in either for the past dozen years
(or anywhere else in the ISI database, for that matter). It must have
been before that.


> I would point out that creationists claim that information is necessary for
> everything biological. But there is not enough information in the DNA to
> define the wiring diagram of your brain. Each brain has about 10^10 neurons
> each with an average of 10000 dendrites (branches). (Michael C. Corballis,
> The Lopsided Ape, (New York: Oxford University Press, 1991), p. 71-72;
> Terrance W. Deacon, "The Human Brain," in S. Jones et al, editors, The
> Cambridge Encyclopedia of Human Evolution, (Cambridge: Cambridge University
> Press, 1992), p. 115)

[trillions of synapses]

I agree, Glenn, that DNA doesn't determine brain wiring, but this is part
of what makes application of the theory so difficult: we really don't
know how many ways there are to wire up a brain. Certainly the number
of neurons factorial is an overestimate by quite a lot. Purkinje cells,
for instance, have a lot of synapses, but the cerebellum is actually one
of the most regular parts of the brain.

I think the fact that we can do molecular biology has contributed to a
sort of 'genetic optomism' where we tend to ignore the important factors
in the somatic environment of the DNA, and the broader environment of the
organism, and think that if we had dino DNA, we could Jurassic Park-ize
them into dinosaurs. This is almost certainly false--dino DNA assumes
it will find itself in dino somatic environments, in Jurassic physical

Just as a final pedantic note in broadcast: information theory is
concerned with ensembles of events/messages/arrangements, and not with
less-well-defined ideas of complexity. If there is only one possibility
for a message, it doesn't matter whether the message is 'BOO' or the
entire Encyclopedia Brittanica; the information content is the same:
zero. That doesn't make information theory outmoded and inadequate,
it just means that if you are going to use it, you have to make an
effort to specify the context of the transmission (source and sink),
the statistics of the messages, and so forth.