From: douglas.hayworth@perbio.com
Date: Fri Sep 26 2003 - 13:06:34 EDT
This distinction Jim makes is more or less correct, but ambiguity in use of
the term "Darwinian" can lead to some false characterization of
evolutionary theory.
I don't think there is an evolutionary biologist alive who doesn't believe
that natural selection is a significant (even the main) mechanism effecting
evolution. Nearly every morphological, physiological, and behavioral
feature that affects how an organism interacts with its environment owes
its properties to the operation of selection. (I say "how the organims
interacts with its environment" because I suppose one could name a number
of features such as silent nucleotide substitutions that don't change the
protein sequence coded as examples where selection is irrelevant to their
fixation or loss in a population). Where people differ is whether and when
other factors are significant alongside selection. For example drift is
very significant in determining the likelihood that a variant will exist
long enough in a population to be able to be selected, but no one really
contends that natural selection is not important.
I think to claim that there is such a wide distinction is a poor
representation of the true consensus of evolutionary biologists.
"Darwinian evolution" is a bad label because it has been used in both
general and specific senses (General=evolution involving natural selection
as a main mechanism. Specific =strong gradualism). This ambiguity of usage
has its origin in evolutionary biology itself; however, the meanings are
distinguished by context within the evolutionary biology discussions. In
wider layperson discussion, the ambiguity adds to confusion, leading people
to think that there isn't much of a consensus in evolutionary biology.
Douglas
"Robert
Schneider" To: <james.behnke@asbury.edu>, <asa@lists.calvin.edu>
<rjschn39@bellso cc:
uth.net> Subject: Darwinian and non-Darwinian (was Re: RFEP & ID)
Sent by:
asa-owner@lists.
calvin.edu
09/26/03 10:54
AM
Jim writes:
> Generally, when we describe someone as a "Darwinian," we are saying that
> they believe that gradualism and selection are the important features in
an
> evolutionary process. It seems that ecologists tend to be hard-core
> Darwinian.
>
> Non-Darwinian biologists view drift, founder effects, macromutations
(those
> with multiple effects) and similar processes as the important mechanisms
in
> an evolutionary pathway. S.J. Gould popularized this in the punctuated
> equilibrium model.
>
> Jim Behnke james.behnke@asbury.edu
> Asbury College
> Wilmore, KY 40390 859-858-3511 x 2232
>
Thanks, Jim. I'm grateful for this statement. But a query. Do not such
phenomena as gene flow, genetic drift, founder effect, etc., still depend
in
some way on selection, as in the establishment of a new population in a new
environment (e.g., migration to an island), even though the rate of
evolutionary change may be much more than gradual? Help me out in
understanding and clarifying this point.
Thanks,
Bob Schneider
(Berea College ex-patriate now in Boone, NC)
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