Tiers of Time and Trials of Extrapolationism 1305
Lyell, as well known and recorded (see Gould, 1987b, for example), named the
epochs of the Tertiary Era by a statistical method based on the percentage of
molluscan species still extant—from Eocene (or "dawn of the recent" for the lowest
percentage) to Pliocene (or "more of the recent" for the much higher percentages of
later strata). He then noted that the uppermost Cretaceous (Maastrichtian) and
lowermost Tertiary beds held no species in common at all. By his argument of
statistical gradualism, this complete non-overlap could only be explained by a vast
gap of missing time—a period long enough to remove all Cretaceous species, one by
one, at the same rate as the Tertiary demise. But since the entire Tertiary did not
suffice to overturn the molluscan fauna completely (as a few Eocene species still
survive), Lyell reasoned that a globally unrecorded interval of time, longer than the
full Tertiary span (so well represented by a voluminous paleontological record
throughout the world), probably intervened between the latest Cretaceous and earliest
Tertiary strata. As Lyell's hypothetical missing interval of more than 65 million years
actually spans only a geological moment under the impact scenario, I would nominate
Lyell's following statement (1833, p. 328) as the worst forecast ever made under the
uniformitarian method of extrapolating from a range of observed rates!
There appears, then, to be a greater chasm between the organic remains of the
Eocene and Maastricht beds, than between the Eocene and Recent strata; for
there are some living shells in the Eocene formations, while there are no
Eocene fossils in the newest secondary [that is, Maastrichtian or uppermost
Cretaceous] group. It is not improbable that a greater interval of time may be
indicated by this greater dissimilarity in fossil remains ... We may, perhaps,
hereafter detect an equal, or even greater series, intermediate between the
Maastricht beds and the Eocene strata.Despite the uniformitarian consensus from Darwin's time until the late 20th
century, occasional scholars of high reputation continued to float catastrophic
proposals for the unresolved puzzle of mass extinctions that, despite the orthodox
conviction about "spreading out" into missing geological time, never meshed well
with gradualist presuppositions and continued, like the proverbial sore thumb, to stick
out above a comfortable background. But, in fairness, we cannot blame geologists
and paleontologists for rejecting these proposals because, to cite a familiar motto,
extraordinary claims require extraordinary evidence—and these attempts to
resuscitate catastrophism remained entirely speculative (or at least undocumented by
anything beyond the basic data for mass extinction itself, an evidentiary source that
had already, to the satisfaction of an entire profession, been rendered consistent with
uniformitarian presuppositions).
To cite the two most notable examples from the generation before Alvarez,
Schindewolf (1963), in an article entitled "Neokatastrophismus," proposed bursts of
cosmic radiation as the paroxysmal mechanism of mass extinction—with direct
nuclear death (for the exterminations) and vast increases in mutation rates among
survivors (for subsequent replacements by highly altered forms).