Re: Adaptationism's Lessons (was Re: Evolution, "adaptation")

John Wilkins (wilkins@wehi.edu.au)
Fri, 13 Sep 1996 13:12:11 +1000

In article <505k5j$du6@argo.unm.edu>, mycol1@unm.edu (Bryant) wrote:

| This new thread is an attempt to clarify some confusing issues about
| adaptationism and Gould's attacks of it. After reading some of my
| exchanges with Lenny, I went back and re-read Gould & Lewontin's 1979
| essay, "The Spandrels of San Marco and the Panglossian Paradigm: A
| Critique of the Adaptationist Programme" (Proc. R. Soc. London, series B,
| 205: 581-598).
|
| I am now thoroughly convinced that the main thrust of the argument in
| that essay is the assertion that adaptationists see wide-spread "perfection"
| (current utility/optimality) everywhere. This is simply untrue.
| Dawkins, one of the "hyper-"adaptationists Gould so dislikes, has
| repeatedly emphasized the role of time lags in evolution.

See also his mentor/inspiration, George C Williams, in the book that
started it all:

"The ground rule -- or perhaps _doctrine_ would be a better term -- is
that adaptation is a special and onerous concept that should be used only
where it is really necessary. When it must be recognized, it should be
attributed to no higher level of organization than is demanded by the
evidence" _Adaptation and Natural Selection_ p 4-5, Princetion UP,
Princeton, NJ, 1966.

This, BTW, is the book where the definition Dawkins so often refers to for
an "evolutionary gene" comes from:

"Any unit of hereditary information for which there is a selection bias
equal to several or many times its rate of endogenous change." 24

This is not the book of a pan-adaptationist, and in his recent book _Why
We Get Sick_, Williams indulges in speculation of adaptationist scenarios
in the full and frank disclosure that it is speculation, not hypothesis,
he and his coauthor are engaging in.

What I think the Williams/Dawkins concept of adaptation requires is that,
if there is a selection bias for a unit of hereditary change (including
cultural units), *then* it must be an adaptation by definition, and what
remains for the researcher is to explain why that unit results in higher
rates of replication (and is therefore by definition an adaptation). The
null hypothesis would be that a structure or function is the result of
history, drift, allometry, etc, etc, which does not require an
adaptationist scenario.

Gould and Vrba's concept of "exaptation" strikes me as relevant here: why
was it proposed? Adaptationists have always recognised that some
adaptations are in fact holdovers from earlier rather than present
selection pressures. I suspect that it was to imply without actually
saying so that selection is insufficient to account for all structures.
Which is true, and not to be denied by anyone.

On pages 20-21 of Williams 1966 book, he says that some biologists (he is
referring to group selectionists and those who refer to NS as anticipating
the needs of a species) tend to make of natural selection the trimmings
for manifestly unDarwinian explanations - "adorning ... arguments with the
forms and symbols of natural selection". But that any useful function that
contributes now or in the past to survival is or was an adaptation is
undeniable overall. Otherwise, it is either the pleiotropic effect of
selection, or is a random or neutral function.
|
| Helena Cronin (author of the adaptationist _Ant and Peacock_, Cambridge,
| 1991), summarizes evolutionists' thinking on the matter thusly:
|
| "Organisms inherit adaptations not to their own environments but those of
| previous generations--and the two may be crucially different." So much
| for current utility and optimality.
|
| Mocking the adaptationist program, Gould & Lewontin quote Voltaire's Dr.
| Pangloss, who said "Things cannot be other than they are...
| Everything is made for the best purpose. Our noses were made to carry
| spectacles..." ...and so on. This is simply not an accurate
| characterization of most neo-Darwinians' position (adaptationism).
|
| As Cronin says more articulately than I could, the problem is that
| critics "are conflating the claim that natural selection is the only
| [creative] evolutionary force with the claim that all characteristics of
| organisms must be adaptive" (p. 86).

Hear, hear

-- 

John Wilkins, Head of Communication Services, Walter and Eliza

Hall Institute of Medical Research

<http://www.wehi.edu.au/~wilkins/www.html><mailto:wilkins@wehi.edu.au>

It is the glory of science that it finds the patterns 

in spite of the noise - Daniel Dennett