758 THE STRUCTURE OF EVOLUTIONARY THEORY
is supposed to be written, being more or less different in the interrupted
succession of chapters, may represent the apparently abruptly changed
forms of life, entombed in our consecutive, but widely separated,
formations.In epitomizing both geological chapters, Darwin begins with a long list of
reasons for such an imperfect record, and then concludes with his characteristic
honesty (1859, p. 342): "All these causes taken conjointly, must have tended to
make the geological record extremely imperfect, and will to a large extent explain
why we do not find interminable varieties, connecting together all the extinct and
existing forms of life by the finest graduated steps. He who rejects these views on
the nature of the geological record will rightly reject my whole theory." (Huxley
must have been thinking of this line when he issued his warning that Darwin's
unswerving support of natura non facit saltum represented "an unnecessary
difficulty." Darwin's "whole theory"— the mechanism of natural selection—does
not require, as Huxley pointed out, this geological style of gradualism in rate.)
The paradoxes set by Darwin's solution for the current practice of
paleontology and macroevolutionary theory receive their clearest expression in
another remarkable statement from the Origin of Species (1859, p. 302), a
testimony to Darwin's sophisticated understanding that nature's "facts" do not stand
before us in pristine objectivity, but must be embedded within theories to make any
sense, or even to be "seen" at all. Darwin acknowledges that he only understood
the extreme imperfection of the geological record when paleontological evidence
of stasis and abrupt appearance threatened to confute the gradualism that he
"knew" to be true: "But I do not pretend that I should ever have suspected how
poor a record of the mutations of life, the best preserved geological section
presented, had not the difficulty of our not discovering innumerable transitional
links between the species which appeared at the commencement and close of each
formation, pressed so hardly on my theory."
The paradox of insulation from disproof
The "argument from imperfection" (with its preposition purposefully chosen by
analogy to the "argument from design") works adequately as a device to save
gradualism in the face of an empirical signal of quite stunning contrariness when
read at face value. But if we adopt openness to empirical falsification as a criterion
for strong and active theories in science, consider the empty protection awarded to
gradualism by Darwin's strategy. For the data that should, prima facie, rank as the
most basic empirical counterweight to gradualism—namely the catalog of cases,
and the resulting relative frequency, for observed stasis and geologically abrupt
appearances of fossil morphospecies—receive a priori interpretation as signs of an
inadequate empirical record. How then could gradualism be refuted from within?
The situation became even more insidious in subtle practice than a bald
statement of the dilemma might suggest. Abrupt appearance (the punctuations