Punctuated Equilibrium and the Validation of Macroevolutionary Theory 1023
wrestled with good argument and content, not primarily with deprecation and
personal attack.
I have mentioned and cited several of these generous reactions, these fair and
accurate characterizations, throughout this section—the journalistic accounts of
Tudge and Gleick (pp. 993, 994); the excellent textbook epitome of Curtis and Barnes
(p. 998); the generous assessment of punctuated equilibrium's scientific importance
by Rhodes (1983); and the acknowledgement of punctuated equilibrium's prod to
further exploration of formulae in population genetics by Cohen (p. 1022). I also wish
to emphasize that most professional colleagues have always given us generous credit,
and have applauded both the debate and the interest generated by punctuated
equilibrium.
I have particularly appreciated the fairness of severe critics who generally
oppose punctuated equilibrium, but who freely acknowledge its legitimacy as a
potentially important proposition with interesting implications, and as a testable
notion that must be adjudicated in its own macroevolutionary realm. Ayala (1982)
has been especially clear and gracious on this point:
If macroevolutionary theory were deducible from microevolutionary
principles, it would be possible to decide between competing
macroevolutionary models simply by examining the logical implications of
microevolutionary theory. But the theory of population genetics is compatible
with both punctualism and gradualism; and, hence, logically it entails neither.
Whether the tempo and mode of evolution occur predominantly according to
the model of punctuated equilibria or according to the model of phyletic
gradualism is an issue to be decided by studying macroevolutionary patterns,
not by inference from microevolutionary processes. In other words,
macroevolutionary theories are not reducible (at least at the present state of
knowledge) to microevolution. Hence, macroevolution and microevolution are
decoupled in the sense (which is epistemologically most important) that
macroevolution is an autonomous field of study that must develop and test its
own theories.Such statements stand in welcome contrast to the frequent grousing of strict
Darwinians who often say something like: "but we know all this, and I said so right
here in the footnote to page 582 of my 1967 paper; you have stated nothing new,
nothing that can alter the practice of the field." I will never forget the climactic
moment of the Chicago macroevolution meeting, when John Maynard Smith rose to
make such an ungenerous statement about punctuated equilibrium and
macroevolutionary theory in general— and George Oster responded to him: "Yes,
John, you may have had the bicycle, but you didn't ride it." In the same vein, I
appreciate the comment of Marjorie Grene (quoted in Stidd, 1985), a famous
philosopher who has greatly aided the clarification of evolutionary theory:
Yet on both these counts—gradualism and neutralism—evolutionists other
than paleontologists now appear unmoved. Just what we've said all along, they
cry, even though, I swear, I've heard, and seen, them