The Essence of Darwinism and the Basis of Modern Orthodoxy 149
reference to natural selection. Gradualism had been equated with rationality itself
by Darwin's chief guru, Charles Lyell (see Chapter 6). All scholars have noted the
centrality of gradualism, both in the ontogeny (Gruber and Barrett, 1974) and logic
(Mayr, 1991) of Darwin's thought.
I will not play "duelling quotations" with "citation grazers," though a full
tabulation of relative frequencies could easily bury their claims under a mountain
of statements. For the present assessment of branch two ("creativity of natural
selection") on the coral of essential Darwinian logic, the necessity of gradualism
will suffice. Selection becomes creative only if it can impart direction to evolution
by superintending the slow and steady accumulation of favored subsets from an
isotropic pool of variation. If gradualism does not accompany this process of
change, selection must relinquish this creative role and Darwinism then fails as a
creative source of evolutionary novelty. If important new features, or entire new
taxa, arise as large and discontinuous variations, then creativity lies in production
of the variation itself. Natural selection no longer causes evolution, and can only
act as a headsman for the unfit, thus promoting changes that originated in other
ways. Gradualism therefore becomes a logical consequence of the operation of
natural selection in Darwin's creative mode. Gradualism also pervades the
methodological pole of Darwin's greatness because the uniformitarian argument of
extrapolation will not work unless change at the grandest scale arises by the
summation through time of small, immediate, and palpable variations.
Gradualism, for Darwin, represents a complex doctrine with several layers of
meaning, all interconnected, while remaining independent in some important
senses. I shall consider three increasing levels of specificity, arguing, on the
Goldilocks model, that one meaning is too nebulous, another overly wrought, but
the third (in the middle) "just right" as the crucial validator of natural selection
(whereas the other two meanings play equally crucial roles for other aspects of
Darwin's view of life).
HISTORICAL CONTINUITY OF STUFF AND INFORMATION. At the broadest level,
gradualism merely asserts unbroken historical connectedness between putative
ancestor and descendant, without characterizing the mode or rate of transition. If
new species originate as creations ex nihilo by a divine power, then connectivity
fails. The assertion of gradualism in this broadest meaning encapsulates the chief
defense for the factuality of evolution. Such a contention could not be more vital to
Darwin's revolution of course, but this sense of gradualism only asserts that
evolution occurred, while telling us nothing about how evolution happens; the
logical tie of gradualism to natural selection cannot reside here.* Thus, this first, or
"too big," sense of gradualism
*Some modern evolutionists have made the error of assuming that contemporary de-
bates about gradualism engage this now obvious and entirely uncontroversial meaning. Thus
Gingerich (1984a), abandoning his earlier and properly empirical approach to gradualism
(sense iii of p. 152) vs. punctuation (1976), argues that gradualism must be true a priori, as
equivalent to "empiricism" in paleontology. He then provides a curious definition of stasis as
"gradualism at zero rate"—an oxymoron with respect to the definition of gradualism that
punctuated equilibrium opposes with a prediction of stasis. I was, at first, deeply