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From: ethan@utastro.UUCP (Ethan Vishniac)
Newsgroups: net.origins
Subject: predicting the course of events
Message-ID: <137@utastro.UUCP>
Date: Fri, 24-May-85 14:56:19 EDT
Article-I.D.: utastro.137
Posted: Fri May 24 14:56:19 1985
Date-Received: Mon, 27-May-85 06:39:50 EDT
Distribution: net
Organization: U. Texas, Astronomy, Austin, TX
Lines: 35

[]
     One consistent argument in this newsgroup has been over the predictive
value of evolutionary theory.  The point has been made that we cannot
predict the course of evolution based on our present knowledge.  The
creationists on the net seem to feel that this implies that the theory
is devoid of predictive value.  A number of people have pointed out that
the theory has nevertheless been used, with considerable success, to
predict data having to do with evolution (e.g. the sequence of fossils,
biochemical relationships, the correspondence between the geological
column and the ages of rocks etc.).

    I wish to address the original point, that evolution is not a predictive
theory in the sense of predicting future evolution.  Many people, of all
persuasions, seem to be willing to accept this.  I think that this is not
true in principle, but only in practice (at present).  After all, we know
that genes carry most of the crucial information about an organism from
one generation to the next.  We are in the process of finding the exact
genetic information carried by a number of simple organisms.  We have begun
to learn how these genes express themselves, and we know how they mutate.
The fact that the mutations are random is irrelevant.  The expression
of the mutations is selected upon.  Although some randomness is built in
to the process, one should be able, eventually, to derive a probabilistic
prediction of future evolution in any specified ecosystem.  If the rate
of evolution is really determined only by the mutation rate and gradualism
is correct, then the probability distribution will tend to be broad.  Although
it should still carry considerable information.  If PE is correct than 
considerably more precise predicitions will be possible.  The point is that
such predictions are not impossible on an a priori basis and we have every
reason to expect that they will become possible eventually.  Verifying such
predictions does appear to have problems.

"Don't argue with a fool.      Ethan Vishniac
 Borrow his money."            {charm,ut-sally,ut-ngp,noao}!utastro!ethan
                               Department of Astronomy
                               University of Texas