950 THE STRUCTURE OF EVOLUTIONARY THEORY
spread of the great Paleozoic marine invertebrate fauna, and the Mesozoic
"modernization" of invertebrate predators and prey (the classic example of a
supposed biotic and gradualistic "arms race")—now seem to occur far more
abruptly in each separate geographic region, with the previous impression of
gradual construction based on a blurring of the different times of transition in each
region (Jablonski, 1999, p. 2114).
In an important paper, Miller (1998) has generalized this claim by
summarizing the increasing evidence for punctuational tempos in faunal change
(both locally and regionally, and for both extinctions and the necessarily slower
rediversifications)—with our conventional notions of gradual flux, particularly for
build-ups, arising as an artifact of summation over displaced timings for rapid
pulses in several regions. Miller first states the general observation and emerging
principles (1998, pp. 1158-1159): "In recent years, local and regional studies of
marine faunal patterns have converged on a similar theme—that biotic turnover
occurred episodically through investigated stratigraphic intervals. There were
comparatively broad intervals with little net turnover, punctuated by narrower
intervals in which many taxa either emigrated or became extinct and were replaced
by a roster of taxa that either originated in the area or immigrated into it. ...
Episodicity appears to be a general feature of regional stratigraphic packages." He
then uses this finding to correct what may be a substantial error in traditional views
(1998, p. 1159): "Thus, major faunal transitions in global-scale compilations,
which seem to have transpired over protracted intervals of geological time, took
place far more rapidly and episodically when evaluated regionally or locally. The
transitions only appear gradual on a global scale because of variations in their
timing from venue to venue."
Finally, Miller asserts a general "fractal" conclusion about punctuational
change (ibid., p. 1159): "The processes that produced major mass extinctions
simply represented the largest and most globally extensive of a spectrum of
perturbations that produced episodic biotic transitions."
As a closing note in this context, Miller also offers a similar punctuational
reinterpretation for the putatively best documented and most widely accepted case
of global, geologically gradual, and broadly progressive change in life's history—
the pattern that Vermeij (1987) has called "escalation" (largely, and with good
reason, to avoid false implications and arguments in the traditional notion of
"progress"), based on relayed "arms race" between predators and their prey, and on
other kinds of similarly reciprocal biotic interaction through extensive time. This
entirely sensible concept of escalation seemed to provide the best available
argument for two deeply rooted and strongly held themes of traditional Darwinian
extrapolationism: the predominant power of biotic interactions to shape patterns in
the history of life, and trends towards the slow accumulation of biomechanically
improved designs in major lineages.
The general argument sounds so reasonable, but when we rethink
macroevolution as a process based upon geologically rapid production of higher-
level individuals by punctuational speciation as the primary units of change,