1312 THE STRUCTURE OF EVOLUTIONARY THEORY
our culturally inherited stories, we should begin to question the complex intellectual
and psychological bases of the hypotheses we have chosen to test.
Moses tried them all (and eventually triumphed, of course). For the most popular
theme of "nuclear winter" and the cutting off of light (and photosynthesis) by a
persisting worldwide dust cloud raised by the impact, "he sent a thick darkness over
all the land, even darkness which might be felt." For acid rain and worldwide fires,
"he gave them hailstones for rain; fire mingled with the hail ran along upon the
ground." For poisoning of the oceans, "he turned their water into blood." For killing
plagues induced by the few successful survivors, "their land brought forth frogs, yea
even unto their King's chambers." And for selective diseases unleashed in this novel
environment, we have the analog of Moses' ultimate weapon: "He smote all the
firstborn of Egypt, the chief of all their strength."
Nonetheless, I do appreciate the undeniably valid part of Glen's contention. For
many scientists and historians have noted that, whereas plate tectonics changed our
view of the earth's structure more profoundly than any previous theory had ever
done—and may even be described as supplying our first adequate account for the
physics of earth-sized bodies in general—plate tectonics also, albeit ironically,
promulgated a conservative reform in not challenging in the slightest way, but rather
supplying a mechanism to validate, the deepest of all geological presuppositions:
uniformitarianism itself. For if the earth's largest mountains can rise as a result of two
plates crunching together at their characteristic moving rate of millimeters per year,
and if the great faultlines, earthquakes and volcanic provinces also mark the edges of
such slowly drifting plates, then the central Lyellian dictum of explaining all grand,
and all apparently quick, events by the accumulation of slow movements, utterly
imperceptible at the scale of our daily lives, gains a kind of planetary and
mathematical validity that can only be deemed awesome in its phenomenological
range and intellectual reach.
On the other hand, Glen continued, the impact theory—even if we never succeed
in establishing this mechanism as a general theory, and even if such catastrophes
remain confined to explanations of particular events—directly fractured Lyellian
uniformity, therefore penetrating far deeper in its iconoclasm than the admittedly
more comprehensive theory of plate tectonics could ever bore. In any case, and in the
terms and concerns of this book, the validation of a truly catastrophic triggering
mechanism for at least some events of mass extinction dramatically fractured the
support that Darwin needed from the kind of geological stage necessarily set for
playing out his preferred game of life. The vital extrapolationist premise of the third
leg on the tripod of essential Darwinian logic must fail if global paroxysm can undo,
redirect, or even substantially impact a pattern of life's history that, in a fully
Darwinian scheme of explanation, must scale up in full continuity from the
microevolutionary realities of competition in observable ecological time.
I have, in my own writings, tried to summarize the theoretical importance of
readmitting truly catastrophic scenarios of mass extinction back into scientific