Punctuated Equilibrium and the Validation of Macroevolutionary Theory 779
to explicate and resolve again and again (Gould and Eldredge, 1977, 1993; Gould,
1982c, 1989e), though without conspicuous success—involves the false
assumption that if we are really saying something radical, we must be staking a
claim for a novel mechanism of speciation, or for a different (read non-Darwinian)
style of genetic change. When our critics then join this false assumption to our
terminology of "unresolvable geological moments" or "punctuations," they begin
to fear that the dreaded specter of saltationism must be lurking just around the
corner, trying yet again to raise its ugly head after such a well-deserved burial.
Vituperation then trumps logic, angry assumption precludes careful reading, and
punctuated equilibrium becomes a loathed doctrine of ignorant and grandstanding
paleontologists who ought to stay in their own limited bailiwick, and get on with
the job of documenting large-scale patterns generated by mechanisms that can be
recognized and comprehended only by neontologists.
But punctuated equilibrium makes no iconoclastic claim about speciation at
all. The radicalism of punctuated equilibrium lies in the extensive consequences of
its key implication that conventional mechanisms of speciation scale into
geological time as the observed punctuations and stasis of most species, and not as
the elusive gradualism that a century of largely fruitless paleontological effort had
sought as the only true expression of evolution in the fossil record. The central
intellectual strategy of our original 1972 paper rests upon this premise. We took
Mayr's allopatric theory (as expressed in his classic treatise of 1963, deemed
"magisterial" by Huxley), and tried to elucidate its implied expression when scaled
into geological time. We did not select this theory to fit a paleontological pattern
that we wished to validate. We choose Mayr's formulation because his allopatric
theory represented the most orthodox and conventional view of speciation then
available in neontological literature—and we had been given the task of applying
standard evolutionary views to the fossil record. I recognize, with 30 years of
hindsight, that our original assessment both of Mayr's theory and of professional
consensus may have been both naive and overly dichotomous, but we could not
have stated our intent more clearly—the reform of paleontological practice by the
paradoxical route of applying a fully conventional apparatus of neontological the-
ory. We wrote (1972, p. 94): "During the past thirty years, the allopatric theory has
grown in popularity to become, for the vast majority of biologists, the theory of
speciation. Its only serious challenger is the sympatric theory. Here we discuss
only the implications of the allopatric theory for interpreting the fossil record of
sexually reproducing metazoans. We do this simply because it is the allopatric,
rather than the sympatric, theory that is preferred by biologists."
Mayr's version of allopatry fit the paleontological pattern of punctuation and
stasis particularly well. If most new species arise from small populations
peripherally isolated at the edges of a parental range, then we cannot expect to
document a gradual transition by analyzing the stratigraphic sequence of samples
for a common species. For we will usually be collecting from the population's
central range during its period of stability. Daughter species