Re: Constraints (was Re: Adaptationism's Lessons)

Bryant (
14 Sep 1996 18:36:00 -0600

Paul Gallagher <> wrote:
> Selection may be the sole cause of adaptation, but the constraints
>on the path of selection may be more interesting as determinants of form.

Or at least *as* interesting.

When I bitch about constraint story telling (Gould's "just how" stories),
I'm talking about folks who present "phylogenetic constraint" as if it's an
*alternative* to adaptationist hypotheses.

What anti-adaptationists seem to miss is the obvious fact that
adaptationism has been a tremendously successful tool for evolutionists.
Little wonder, then, that we're reluctant to return to the bad old days,
described by Mayr (1982), when evolutionists tended to "ascribe to
genetic drift almost any puzzling evolutionary phenomenon."

If selection were not so powerful a force, the randomizing forces of
mutation and drift would preclude functional organisms in the first place!

I find it highly ironic that Gould & Lewontin (in their infamous
spandrels paper) quote Wallace's comments on land snail shell banding as the
epitome of "Panglossian hyperadaptationism," only to have Wallace proven
correct a few years later!

Likewise, Arrow (1951) concluded that beetles' horns in _Bolitotherus_
were incidental side effects of developmental processes. The result,
as Thornhill & Alcock describe in their _Evolution of Insect Mating
Systems_ (1983), was for research on the trait to cease. Only three
decades later did Eberhard and Brown show that males use their horns to remove
copulating competitors from females. The horns were not designed for
impaling, but as levers.

Now days, drift's the explanation of last resort, after testable adaptation
hypotheses are abandoned. As it should be. Otherwise, we abandon
prediction-testing science and become conjecturing historians of life.

Gould's indeed contributed to evolutionary theory. But he has, as others
have pointed out, offered mostly minor corrections, not revolutionary
insights. Most of these corrections were articulated long before Gould,
yet he still credits himself with them (e.g., the "Panda Principle" I
mentioned earlier in this thread). (That's ok; the notions which Dawkins
became famously associated with were first articulated by Williams!)



Arrow, 1951. _Horned Beetles_. The Hague: Dr. W. Junk.

Mayr, 1982. _The Growth of Biological Thought_. Harvard Univ. Press.