Tiers of Time and Trials of Extrapolationism 1309
the same scientific language (most notably of Linnaean Latin vs. Newtonian triple
integral signs). Paleontologists met, and even eventually published papers with,
colleagues who had formerly received little more than a grunted "hello" in 20 years of
hallway passing, or who had only been seen as strangers across a crowded room
during some unenchanted evening at a faculty party. The several Snowbird
conferences in Utah will never be forgotten by anyone who enjoyed the privilege of
attendance, and who participated in the warm fellowship, and sometimes-antic
debate, with (among many others) nuclear physicists, taxonomic paleontologists, and
historians of science.
- Most importantly, and diagnostically for scientific practice, the impact
hypothesis proved its mettle (at least for me) in the explicit suggestions and prods
that it provided for particular (and ultimately highly fruitful and exciting)
paleontological research that would never even have been conceptualized without its
nudge and encouragement. I have argued throughout this book that the broad world-
views of scientists (with gradualism, uniformitarianism, and strict Darwinian
adaptationism as the major examples in this context) do not merely act as passive
summaries of general beliefs, but serve as active definers of permissible subjects for
study, and modes for their examination. At best, a potent context continually
provokes more fruitful work. But at worst, and (unfortunately) ever so often in the
history of science, such world-views direct and constrain research by actively
defining out of existence, or simply placing outside the realm of conceptualization, a
large set of interesting subjects and approaches, often including the very classes of
data best suited to act as potential refutations of the world-view. Such self-referential
affirmations are not promoted cynically, or (for the most part) even consciously, but
they do, nonetheless, operate as strong impediments to scientific change.
As argued throughout Chapter 9, my greatest pride in punctuated equilibrium
lies in the theoretical space it created for active study of subjects that could win
neither definition nor existence under gradualistic presuppositions: particularly stasis
(previously viewed as an embarrassing failure to detect evolution, and therefore as a
non-subject), now generally seen as an important and surprising result at several
levels in the history of life; and the punctuational explanation of trends by differential
success of species treated as discrete Darwinian individuals (an alternative with
explanatory options that simply didn't exist under older models of trends defined
exclusively as anagenetic transformation). In several similar ways—I will cite just
two here—the catastrophic impact hypothesis of mass extinction created an enlarged
intellectual space that forced paleontologists to reevaluate data once viewed as
comfortably consistent with gradualist assumptions, but clearly subject to extension
and better definition as tests for gradualism vs. catastrophe. In this vital way, self-
fulfilling claims for convention became sources for discrimination among rival
hypotheses about some of the most important questions in the history of life.
For example, in a justly influential paper, Signor and Lipps (1982) recognized
that the well-documented literal signal of taxa slowly "petering out" in the
stratigraphic record before a mass extinction boundary might actually