756 THE STRUCTURE OF EVOLUTIONARY THEORY
and precluding the explanation of trends and other macroevolutionary patterns as
extrapolations of anagenesis within populations.
Rather, punctuated equilibrium refutes the third and most general meaning of
Darwinian gradualism, designated in Chapter 2 (see pp. 152-155) as "slowness and
smoothness (but not constancy) of rate." Natural selection does not require or
imply this degree of geological sloth and smoothness, though Darwin frequently,
and falsely, linked the two concepts—as Huxley tried so forcefully to advise him,
though in vain, with his famous warning: "you have loaded yourself with an
unnecessary difficulty in adopting Natura non facit saltum so unreservedly." The
crucial error of Dawkins (1986) and several other critics’ lies in their failure to
recognize the theoretical importance of this third meaning, the domain that
punctuated equilibrium does challenge. Dawkins correctly notes that we do not
question the second meaning of insensible intermediacy. But since his
extrapolationist view leads him to regard only this second meaning as vital to the
rule of natural selection, he dismisses the third meaning—which we do confute—
as trivial. Since Dawkins rejects the hierarchical model of selection, he does not
grant himself the conceptual space for weighing the claim that punctuated
equilibrium's critique of the third meaning undermines the crucial Darwinian
strategy for rendering all scales of evolution by smooth extrapolation from the
organismic level. For this refutation of extrapolation by punctuated equilibrium
validates the treatment of species as evolutionary individuals, and establishes the
level of species selection as a potentially important contributor to
macroevolutionary pattern.
This broadest third meaning of gradualism may not be required for natural
selection at the organismic level, but gradualism as slowness and smoothness of
rate (not just as insensible intermediacy between endpoints of a transition) forms
the centerpiece of Darwin's larger worldview, indeed of his entire ontology—as
illustrated (again, see Chapter 2) in the crucial role played by this style of
gradualism throughout the corpus of his works—from his first book on the origin
of coral atolls (1842) to his last on the formation of topsoil by the action of worms
(1881).
Lest anyone doubt that Darwin strongly advocated this most inclusive form of
gradualism as slowness and smoothness (in addition to the less comprehensive
claim for insensible intermediacy of transitions), I shall cite a few examples from
the full documentation of Chapter 2—cases where Darwin clearly meant "slow and
steady over geological scales," not just "insensibly intermediate at whatever rate."
For example Darwin argues that species may arise so slowly that the process
generally takes longer than the entire duration of a geological formation (usually
several million years)—thus explaining apparent stasis within a formation as
gradual evolution over insufficient time to record visible change! Darwin writes
(1859, p. 293): "Although each formation may mark a very long lapse of years,
each perhaps is short compared with the period requisite to change one species into
another." Darwin even argued that the pace of evolutionary change might be
sufficiently steady to serve as a rough geological