1024 THE STRUCTURE OF EVOLUTIONARY THEORY
emphatically assert just the opposite, time and time again. No sudden changes,
no non-adaptive changes, they used to exclaim, while now they ask
cheerfully: why not stasis, sudden change, and neutral mutations all over the
place except for an adaptive innovation here and there, now and then? We
always knew it was like that. Nothing really new, no revolution here.Finally, I am heartened by the many top-ranking biologists who have found
fruitful ideas and new wrinkles in the concept of punctuated equilibrium and its
macroevolutionary implications—for utility in practice remains the ultimate criterion
of judgment in science. I appreciate Dan Janzen's affirmation in his article "on
ecological fitting" (Janzen, 1985, p. 308): "I suddenly realize that I have blundered
through the front door of the turmoil over punctuated equilibria. We don't have to dig
at the fossil record; punctuated equilibria are right here in front of us, represented by
most of the species that you and I have anything to do with."
I welcome the generous assessment of Kenneth Korey (1984) in the preface to
his compendium of Darwin's best writing, The Essential Darwin:
Unquestionably no single challenge to the synthesis has provoked more
attention than the theory of punctuated equilibrium advanced by Niles
Eldredge and Stephen Gould. ... It is true that punctuated equilibrium was not
a prediction of the synthesis; on the contrary, Simpson emphasized
continuous, phyletic evolution as the most pervasive feature of evolution at
this level... On the macroevolutionary front... punctuated equilibrium as an
empirical proposition is not, perforce, in conflict with the synthesis, although
if its wide province becomes established, then a more complete theoretical
explanation for stasis will certainly be wanted. Species selection, in its present
form, would seem to require the most profound reworking of evolutionary
theory.And I thank Paul Ehrlich (1986) for recognizing the genuine novelty and utility
of punctuated equilibrium in his book, The Machinery of Nature:
The jury is not in on the punctuated-equilibria controversy. That the "snapshot" of
differentiation we see today seems to reveal all stages of differentiation does not
necessarily signal a win for the gradualists... And it is not fair to swallow the
punctuationist view within the gradualist orthodoxy simply because the possibility
of rapid speciation has always been part of that orthodoxy. The punctuationist view
is about dominant patterns, not about what is possible—and it represents a genuine
challenge to one widely held tenet within evolutionary theory.It has been a wonderful ride on Oster's bicycle, and we still have such a long
road to travel.