Punctuated Equilibrium and the Validation of Macroevolutionary Theory 1015
single point (for example, see Gruber [1974] and Mayr [1982b]), it is the
importance and pervasiveness of Darwin's gradualism—a commitment far
stronger than his allegiance to natural selection as an evolutionary mechanism.Fortunately, one needn't take my partisan word in refutation. Frank Rhodes, then
the president of Cornell University, but a distinguished paleontologist by training and
first career, became interested in punctuated equilibrium and its links to the history of
evolutionary thought. He therefore spent a sabbatical term researching the
relationship of Darwin's thinking to the claims and tenets of punctuated equilibrium.
He did find many genuine Darwinian resonances, while affirming our originality and
concluding, "the hypothesis of punctuated equilibrium is of major importance for
paleontological theory and practice" (Rhodes, 1983, p. 272).
When Gingerich (1984, p. 116) wrote a commentary on Rhodes's article,
dedicated to denying our originality and asserting once again that Darwin had said it
all before, Rhodes replied with generosity and firmness (under Gingerich, 1985, p.
116):
I do argue that punctuated equilibrium—whether true or false—is a
"hypothesis of major importance" and that it has had a beneficial impact on
the quality of recent paleontological studies. Gingerich asks, "Which nuances
[of punctuated equilibrium] were unanticipated by Darwin?" From a long list,
I suggest the following: its relationship to the genetics of stasis and the
punctuation, morphological stasis and developmental constraints, evolutionary
models in relation to paleoecology, stratigraphical correlation, species
selection, mathematical models of evolutionary rates, selection of RNA
molecules, phylogenetic divergence, and the evolution of communities. These
topics, and many more studied from the viewpoint of punctuated equilibrium,
have been the subject of recent papers ... To suggest that there was no nuance
of punctuated equilibrium which was "unanticipated by Darwin" is to make an
icon of Darwin and to adopt an extravagantly Whiggish view of the history of
Darwin's particular contribution—great as that was.Some critics then followed a substitutional strategy: if one denigration fails, try
another in the same form. If "Darwin said it all" fails as an optimal dismissal, then try
the best available paleontological version: "G. G. Simpson said it all." Again, the
search for reinterpretations and footnotes began, as this new version of denigration
began to coagulate among our most committed detractors: Simpson (1944) devoted
his seminal book to documenting the great variation in evolutionary rates, and
punctuated equilibrium therefore has nothing new to say.
But, punctuated equilibrium was never formulated as a hypothesis about great
variability in anagenetic rates (which, indeed, everyone has long acknowledged).
Punctuated equilibrium presents a specific hypothesis about the location of most
evolutionary change in punctuational cladogenesis, followed