750 THE STRUCTURE OF EVOLUTIONARY THEORY
they do not read. The longterm stasis, following a geologically abrupt origin, of
most fossil morphospecies, has always been recognized by professional
paleontologists, as the previous story of Hugh Falconer testifies. This fact, as
discussed on the next page, established a basis for bistratigraphic practice, the
primary professional role for paleontology during most of its history.
But another reason, beyond tacitly shared knowledge, soon arose to drive
stasis more actively into textual silence. Darwinian evolution became the great
intellectual novelty of the later 19th century, and paleontology held the archives of
life's history. Darwin proclaimed insensibly gradual transition as the canonical
expectation for evolution's expression in the fossil record. He knew, of course, that
the detailed histories of species rarely show such a pattern, so he explained the
literal appearance of stasis and abrupt replacement as an artifact of a woefully
imperfect fossil record. Thus, paleontologists could be good Darwinians and still
acknowledge the primary fact of their profession—but only at the price of
sheepishness or embarrassment. No one can take great comfort when the primary
observation of their discipline becomes an artifact of limited evidence rather than
an expression of nature's ways. Thus, once gradualism emerged as the expected
pattern for documenting evolution—with an evident implication that the fossil
record's dominant signal of stasis and abrupt replacement can only be a sign of
evidentiary poverty—paleontologists became cowed or puzzled, and even less
likely to showcase their primary datum.
But this puzzlement did sometimes break through to overt statement. For
example, in 1903, H. F. Cleland, a paleontologist's paleontologist—that is, a
respected expert on local minutiae, but not a general theorist—wrote of the famous
Devonian Hamilton section in New York State (which has since become the "type"
for an important potential extension of punctuated equilibrium to the integrated
behavior of entire faunas, the hypothesis of "coordinated stasis"—see pp. 916-
922):
In a section such as that of the Hamilton formation at Cayuga Lake ... if the
statement natura non facit saltum is granted, one should, with some
confidence, expect to find many—at least some—evidences of evolution. A
careful examination of the fossils of all the zones, from the lowest to the
highest, failed to reveal any evolutional changes, with the possible
exception of Ambocoelia praeumbona [a brachiopod]. The species are as
distinct or as variable in one portion of the section as in another. Species
varied in shape, in size, and in surface markings, but these changes were
not progressive. The conclusion must be that... the evolution of
brachiopods, gastropods, and pelecypods either does not take place at all or
takes place very seldom, and that it makes little difference how much time
elapses so long as the conditions of environment remain unchanged (quoted
in Brett, Ivany, and Schopf, 1996, p. 2).But far better than such explicit testimonies—and following various
gastronomical metaphors about the primacy of practice (knowing by fruits, proofs
of the pudding, etc.)— the most persuasive testimony about dominant