Change over time v. Gene freqs?

Sun, 10 Mar 1996 09:03:00 CDT

This is one of the things that causes us trouble in getting people to understand
(and accept evolution). As someone pointed out so eloquently, most creationists
have no trouble with the idea that gene frquencies change -- the sort of
microevolutionary things that population geneticists study. They would argue,
however, that these changes do not and cannot (and there is no proof that they
can or do) translate into the emergence of new species and new biological forms
or functions.

I perceive a problem with the minimalist definition of evolution as a "change in
gene frequencies." After all, the genes in the North American branch of my
family certainly display different frequencies from those in Tuscany. Can we
be said to have "evolved" in the last 8 decades? If not, then how should the
distinction be understood?

One solution, I think, is to make it clear that changing genes (and gene
frequencies) are a *mechanism* by which evolutionary change occurs -- after all,
we still are convinced that the structures and functions we can observe are
somehow expressed out of genetic information -- but we also recognize that a lot
of variations occur in gene frequencies that we would not qualify as
*evolutionary* change, except in the very loosest sense.

THe changes in gene frequencies that ARE related to evolution are those that
result (ultimately) in the appearance of new species (or new higher taxa), new
structures and/or new functions in gross or molecular perspective. The problem,
of course, is that we can never tell whether any specific pattern of genetic
change will lead to evolutionary change -- at least not while it is happening.

So, the "fact" of evolution is that we look back over the history of the earth
and see the emergence of new forms of life and new structures. We know that the
genes are the things that are responsible for the construction, development,
operation, and change in these structures. *We* make the connection between
genes and evolution -- a reasonable analysis to be sure -- but they are not the
same thing. As Jon MArks has said so many times, for all we know about genes
and sequences and DNA, we still have no more idea about how to make a nose than
Mendel did over a century ago. We know that the genes are important --
essential -- to this process, but that is about as far as it goes.

Andrew J. Petto, Editor, National Center for Science Ed.
c/o Dept. of Anthropology, University of Wisconsin
1180 Observatory Drive, MADISON WI 53706-1393
voice: 608/259-2926; fax:608/258-2415
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