798 THE STRUCTURE OF EVOLUTIONARY THEORY
some validity, and might now be subject to overly curt and confident dismissal.)
This situation creates a paradox for our theory. The pattern of punctuated
equilibrium has been well documented and shown to predominate in many
situations (see pp. 822-874), but its most obvious theoretical rationale has now
fallen under strong skepticism. So either punctuated equilibrium is wrong—a
proposition that this partisan views as unlikely (although obviously possible),
especially in the face of such strong documentation—or we must identify another
reason for the prominence of punctuated equilibrium as a pattern in the history of
life. In our article on the "majority" (21st birthday!) of punctuated equilibrium,
Eldredge and I expressed this dilemma in the following manner (Gould and
Eldredge, 1993, p. 226): "The pattern of punctuated equilibrium exists (at
predominant relative frequency, we would argue) and is robust. Eppur non si
muove; but why then? For the association of morphological change with speciation
remains as a major pattern in the fossil record." (Our Italian parody, missed by
many readers of the original article, alters Galileo's famous, but almost surely
legendary, rebuke to the Inquisition, delivered secretly and sotto voce after he had
been forced to recant his Copernican views in public: Eppur si muove—
nevertheless it does move. Our parody says "nevertheless it does not move"—a
reference to the overwhelming evidence for predominant stasis in the history of
species, even if our original evolutionary rationale, based on population size, must
be reassessed.)
This paradox permits several approaches, including the following two that I
would not favor. One might simply argue that the pattern of punctuated
equilibrium demonstrably exists, so the task falls to evolutionary theorists to find a
proper explanation. The current absence of a satisfactory account does not threaten
the empirical record, but rather directs inquiry by posing a problem. Or one might
doubt that any single explanation can render the phenomenon, and suspect that
many rationales will yield the observed pattern (including Mayrian genetic
revolutions, even if we now regard their relative frequency as low). Thus, we need
to identify a set of enabling criteria from evolutionary theory, and then argue that
their combination may render the observed phenomena of the fossil record.
Most researchers would regard a third approach as preferable in science: an
alternate general explanation of different form from the previous, but now rejected,
leading candidate. I believe that such a resolution has been provided by Douglas
Futuyma (1986,1988a and b, but especially 1987), * although his
- Futuyma remains quite skeptical of punctuated equilibrium in general, and I would
place him more among our critics than our supporters. But he does accept the empirical
pattern, and he is an expert on speciation. Thus, when he developed an original way to
resolve the paradox of why punctuations might correlate with events of speciation, even if
processes of speciation don't accelerate the rate of evolution, he published his ideas as a
constructive contribution to the general debate. Even though Futuyma disagrees with our
claims for the general importance of punctuated equilibrium (while he, obviously, does not
deny the phenomenon), he has granted us serious attention and has acknowledged the
intellectual interest of the debate we provoked—and no one could ask for more from a good
critic. Futuyma wrote (1988, p. 225), in stressing the need to integrate "synchronic"
approaches