Reflectorites
On Tue, 17 Oct 2000 04:28:00 -0500 (CDT), Wesley R. Elsberry wrote:
WE>I find it amusing that work on genetic algorithms is critiqued
>as not providing a complete simulation of all the nuances of
>biological reality when the same critics apparently wish us to
>accept Schutzenberger's even less nuanced simulations as
>relevant. The irony there is precious.
Well since even "Schutzenberger's ... less nuanced simulations" didn't
work either, the "irony" seems to be on Wesley!
WE>Of course, if it hadn't been for Bradbury, I might have missed
>out on that dose of irony completely. I've put Jones in an
>"archive-unread" filter, as well as "DNAunion".
That is fine by me!
WE>The quote with Waddington saying that he wasn't interested in
>Schutzenberger's computers is often quoted out of context.
>In isolation, it makes it look like some distressed non-techie
>biologist is simply frustrated with an elegant argument given
>by Schutzenberger. In fact, though, Waddington had another and
>better reason for being short with Schutzenberger, which was that
>Schutzenberger was digressing away from a concrete biological
>counter-example given by Lewontin. Waddington's interjection
>comes at Schutzenberger's fifth "reply" to Lewontin, which
>nonetheless failed to answer Lewontin's direct question.
Berlinski has a different interpretation:
"This is an observation first made by M. P. Schutzenberger. "If we
try to simulate such a situation [i. e., life] on the computer" he
remarked at the 1966 Wistar Symposium, "we find that we have no
chance even to see what the modified program would compute; it
just jams." Biologists hearing Schutzenberger out with their usual
attitude of anxiety and aggressiveness, misunderstood the point
entirely. Richard Lewontin, for example, - strange how many of
these sad sacks come from Harvard insisted perversely that
whatever works in life, works, a thesis not under dispute. "Can I
give you a practical experience," he argued in full voice, "where
there is no jamming and no loss of meaning?" That practical
experience turned out to be a description of the formation of
tryptophane synthetase. Patiently Schutzenberger explained to
Lewontin that what was at issue was not whether life works, but
how it works, another matter entirely. As the discussion proceeds -
these verbatim records are a source of great amusement- everyone
becomes progressively more befuddled; from time to time,
Schutzenberger managed to swirl his cape to fact the panting
Lewontin, but the artistic effect is spoiled for the reader by the
peevishness of the exchanges." (Berlinski D., "Black Mischief:
Language, Life, Logic, Luck", 1988, p333)
WE>Dr. Alex Fraser contrasted Schutzenberger's simulation scenario,
>which did not work, with a version that did work.
>
>[Quote]
>
>Dr. Fraser: Can I contrast one computer with another? You
>have a computer programmed to examine the statement, "All I am
>allowed to do is change letters and I hope I produce a
>program. Any kind of program will do." This doesn't work.
>We now turn around and set up another computer, and we tell it
>a basic genetic system of plus-minus alleles in which we are
>saying, "Can it produce information?" The decision on whether
>the information is useful will be a selective one of "survive
>or not survive." This is the same kind of decision-making;
>the programs look very similar to those which are being
>constructed to try to produce information-containing programs.
>The principles are very similar.
> However, in the genetic one, the system is that there are
>multiplicities of pathways to suitable answers. The machine
>can gradually, step by step, get there; each step takes it
>toward the answers, and it produces them when all we have fed
>into the machince is a genetic system of essentially complete
>simplicity. What is surprising is how fast rational information
>is produced by the machine within the meaning of the original
>context.
And what, pray tell, are "suitable answers"?
WE>So, if you are going to take a program space and say, "We cannot
>transform it," but leave out of it the means of combination
>and recombination in between and of evolution by selection,
>I am certain that your program will not produce sense; but if
>you put it in there the machine gets there so fast it is
>surprising.
>
>[End Quote - Dr. A Fraser, discussion of Schutzenberger's paper,
>"Mathematical challenges to the Neo-Darwinian interpretation of
>evolution", p.80]
And what was Schutzenberger's reply?
Steve
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"These simulations of prebiotic chemistry began with the efforts of Stanley
Miller in Chicago. In the early 1920s, Miller found that many of the amino
acids used by modern life are formed in unexpected abundance when
mixtures of gases such as, methane, ammonia and water vapour, probably
present in the primordial atmosphere, are exposed to "lightning storms" in
the form of electric sparks. Further simulations by Miller himself and many
other researchers such as Carl Sagan at Cornell and Juan Oro in Houston,
have yielded most of the other building blocks of life. Although some
problems remain (nucleotides, for example, have proved difficult to
produce, and the conditions required to make different important products
sometimes appear incompatible), even critics of the established theories
accept that life's simple building blocks were probably available on the early
Earth. This view is strengthened by the discovery of a wide range of amino
acids, purines, pyrimidines (components of nucleic acids) and other organic
compounds in the meteorites that reach us from space. Difficulties arise
when we try to take the simulation process any farther, by leaving the
amino acids, nucleic acids, fats and carbohydrates lying around in the
conditions expected to have prevailed on primitive Earth. Genes, enzymes,
molecules of transfer RNA and living cells do not, of course, arise with as
much ease as their basic components. The ultimate proof of the modern
theory of genesis-the emergence of life from the "test tube"cannot be made
to work. At least not yet." (Scott A., "Update on Genesis," New Scientist,
Vol. 106, No. 1454, 2 May 1985, pp.30-33, p.30)
Stephen E. Jones | Ph. +61 8 9448 7439 | http://www.iinet.net.au/~sejones
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