Darwin-L Message Log 5:79 (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.

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<5:79>From KIMLER@social.chass.ncsu.edu  Fri Jan 14 14:13:34 1994

From: KIMLER@social.chass.ncsu.edu
To: darwin-l@ukanaix.cc.ukans.edu
Date: Fri, 14 Jan 1994 15:22:16 EST5EDT
Subject: Re: NeoDarwinism debates

I hasten to post this _before_ Ron Amundson provides his
bibliography of recent developmentalist challenges to the Modern
Synthesis, because I don't want it to be seen as discussing
particular, individual cases of research and interpretation.  Rather,
this is a general historical and analytical comment about the scope
and defense of NeoDarwinism.  The issue has some relevance for the
comparisons of biological evolution to linguistics and other Darwin-L
topics.  Put most bluntly, the argument in the founding of the modern
theory (roughly, 1930s) was about (1) the control of the direction of
evolution, and (2) the adequacy of natural selection to direct
change.  The second point was demonstrated in population genetics
theory and practice, and I don't believe that any serious challenge
has yet denied that demonstration.  Organismic selection has been
supplemented by other mechanisms that could also be operating, or
especially by other levels at which selection could or does work.

Most current or recent "challenges" to the adequacy of Darwinism
have attempted to put some real substance into the vaguely
articulated, usually invoked caveat that there exist "constraints" on
the full randomness of variation.  This issue must, however, be
expressed in terms that capture the essence of modern Darwinism, or
else people talk past each other.  Anyone who watches the debates
from the outside will notice a maddening inability to clearly define
camps, or opposition. Punctuated equilibrium, for instance, is
suggested by some adherents to be a radical overthrow of conventional
Darwinism, but seen by other adherents as just a necessary wrinkle on
standard theory, elevating to notice pieces that were undervalued.
That, of course, is a line taken by many critics of punctuated
equilibrium as well.  The same general situation, it seems to me,
exists for "developmental constraints." Traditional Modern Synthesis
proponents say, oh sure, we've always admitted that.  Some
developmentalists say, o.k., but now take us seriously.  Others claim
to be radical and overthrowing NeoDarwinism [it seems that getting
notice by claiming to be a radical is a recurrent theme on Darwin-L].

To this historian, one way out of conceptual confusion is to step
back and use different labels, to highlight the underlying issue.
In this case, there already exist labels used by the biologists
themselves in first arguing the issue.  At Oxford, Edward Poulton in
the early 1900s identified the problem in the process of evolution
as control of its direction, and called it Externalism versus
Internalism.  The selectionists were thus posed against
orthogeneticists, because the latter used internal rules of
direction, no matter what their particular mechanism (genetic,
developmental, inherent life-spans of species or higher taxa).  The
new Mutationstheorie and Mendelism were both Internalist: they
granted the control of evolution to internal directors, making
selection at best a minor refiner of species traits.  The only
Externalist competitor to natural selection was Lamarckism, which
was being rejected by both selectionists and internalists.
Internalists lost the early round because they couldn't identify the
rules or cellular mechanisms, nor explain how ecological adaptation
came about from internally driven directions.

The possibilities still are externalist natural selection and a
number of internalist mechanisms suggested to be powerful enough to
be the true director of evolution.  I submit that the Synthesists
knew that there had to be practical constraints (cf. Fisher's
argument for the necessity of gradualism, if you want an ironic
twist), but that (1) their rhetorical enterprise was rescuing
selection from nearly complete neglect, and (2) the fields of
developmental biology and genetics could provide no good cases of
overwhelming the importance of selection.  The job for modern
challengers to the primacy of selection is provide cases. How much
can be made explicit about rules, to force the issue beyond generic
statements on the existence of constraints?  I'm rather skeptical of
most claims of being radical or revolutionary, and in this case am
not sure that NeoDarwinism is being overthrown anyway. Selection has
been demonstrated to be powerful.  Expansive, still consistent theory
can incorporate when and where other biological processes step in to
be more important as the "director."  There will always need to be a
selectionist caveat among internalists: in what ways are internal
rules a matter of selective processes at molecular or cellular levels
(a question posed by Weismann, by the way)?  Biologists have figured
out by now that it's a terribly messy world.

On a related point, Poulton in the 1890s, and then his intellectual
successor E. B. Ford in the 1930s, used the existence of
developmental constraints to argue FOR selection as the most
important director.  They both worked on the coloration of
butterflies, and problems of convergence.  Internalists wanted to
explain similar colors in different species by invoking parallel
physiological or genetic rules.  Poulton and Ford examined a few
cases of similar colors appearing in taxonomically unrelated species,
found the biochemical nature of the color, and showed how each had a
different biochemical lineage but had been molded to mimetic
convergence by natural selection.  Though giving up an infinitely
plastic supply of variation and molding, they still needed selection
to explain why the species fit the world in particular ways.

Where's the connection for non-biologist readers of the List?  It
seems that most historical processes need to be examined with the
dualism of internal rules and external circumstances.  Identifying
oneself as internalist or externalist is a way of quickly evoking
what one thinks the primary or exclusive directing mechanism.  If you
believe it's of course both, then call yourself an historian!

William Kimler
Department of History
North Carolina State University

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