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Darwin-L Message Log 5:67 (January 1994)

Academic Discussion on the History and Theory of the Historical Sciences

This is one message from the Archives of Darwin-L (1993–1997), a professional discussion group on the history and theory of the historical sciences.

Note: Additional publications on evolution and the historical sciences by the Darwin-L list owner are available on SSRN.


<5:67>From DARWIN@iris.uncg.edu  Wed Jan 12 22:43:49 1994

Date: Wed, 12 Jan 1994 23:49:40 -0500 (EST)
From: DARWIN@iris.uncg.edu
Subject: Re: Status of anti-neo-Darwinism?
To: darwin-l@ukanaix.cc.ukans.edu
Organization: University of NC at Greensboro

It's been a while since I've looked at the Brooks and Wiley work on evolution
and entropy, but I just wanted to put in my two cents on John Wilkins's more
general question about the status of "neodarwinism."

"Neodarwinism" refers to the general understanding of the evolutionary process
that developed first in the period of the "Modern Synthesis" of the 1930s and
1940s.  A tiny sketch of the relevant history would go like this: after 1859
most people accepted the theory of descent but relatively few accepted natural
selection as the mechanism of evolutionary change; fewer and fewer as we
approach 1900.  By 1900 natural selection was very unpopular but descent was
universally accepted.  Round about the 1930s a number of lines of evidence
converged from genetics, biogeography, and population systematics that caused
natural selection to be accepted as the principal mechanism of evolutionary
change once again.  This convergence of a variety of lines of evidence was
called the "Modern Synthesis", and it is usually associated with the work of
people like Mayr, Dobzhansky, Wright, Fisher, Haldane, Simpson, Stebbins, and
many others.  "Neodarwinism" is the term that is usually applied to the views
of this period: "darwinism" because it represented a revival of natural
selection as the principal mechanism of change, and "neo" because it did
replace or discard certain elements of Darwin's own views, most notably
Darwin's belief in "soft inheritance" (Lamarckian inheritance).

In the last ten or twenty years, however, a number of people who have made
an assortment of discoveries have declared as a result of their work that
"neodarwinism is dead!"  The problem with this is that neodarwinism isn't
some singular proposition that can be declared true or false; it's a whole
constellation of work that includes most of 20th-century population genetics,
the rejection of soft ("Lamarckian") inheritance, the notion that speciation
usually requires geographical isolation (allopatry), the adoption of
"population thinking" and the rejection of essentialism, and on and on.
The claim that neodarwinism has been proven false is somewhat like saying:
"Senator X was elected by a majority of the people in his state, but we have
proof that Senator X is an embezzeler.  Thus democracy is a complete failure
as a system of government, because embezzelers are elected to office under
democracy."

"Ah, but the fact that the third position in a DNA codon can drift randomly
and is not subject to selection destroys the whole neodarwinian edifice!"
I don't see how such a claim can be defended when in the very paragraph in the
_Origin_ where Darwin defines natural selection he speaks of variations which
are neither useful nor injurious remaining as a fluctuating element within any
population.

"Ah, but some speciation is not allopatric!"  Of course.  Is that a death-blow
to the modern synthetic theory of evolution?  Hardly.

"Ah, but what about punctuated equilibrium!"  A "minor gloss on neodarwinism"
as someone recently said.

"Ah, but organismal variation is constrained within certain limits; organisms
don't vary equally in all directions and so can't be molded like clay!"  Yes,
that's right.  Did anybody ever really believe otherwise?  (If anybody did
believe otherwise, well, I'm sure the Synthesis folks got a few things wrong
here and there, like we all do.  No big deal.)

Now, are there specific and interesting questions that can be asked about any
of these particular points?  Absolutely.  Just what conditions must be met for
sympatric speciation to occur?  What is the nature of the the constraints on
variation and how do they themselves vary across taxa and through time?  How
important is random drift in populations of different structures and sizes?
All of these are very interesting and valuable questions one may ask.  But
each one of these questions must be framed in a very specific manner.  For a
really good example of interesting questions within the neodarwinian framework
take a look at George C. Williams new book _Natural Selection_ (Oxford Univ.
Press, 1992).  I think Williams's discussion of the notion that particular
taxa have their variation constrained by "bauplans" is particularly good.

Some time last semester _Time_ magazine had a cover story about dinosaurs with
the bold headline "Dinosaurs: Everything you know about them is wrong!"  One
of my students looked at me with a sort of worried look when he saw it and
said "Everything I know is wrong?" I told him not to worry; it's how they sell
magazines.  I guess I feel the same way about "Neodarwinism is dead!": it's an
eye-catcher for sure, but by itself I'm not sure it's a whole lot more.

Bob O'Hara, Darwin-L list owner

Robert J. O'Hara (darwin@iris.uncg.edu)
Center for Critical Inquiry and Department of Biology
100 Foust Building, University of North Carolina at Greensboro
Greensboro, North Carolina 27412 U.S.A.

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