Punctuated Equilibrium and the Validation of Macroevolutionary Theory 763
(the "Irish Elk") increased gradually in phylogeny, with positive allometry as body
size enlarged.
Traditional paleontology therefore placed itself into a straight jacket that
made the practice of science effectively impossible: only a tiny percentage of cases
passed muster for study at all, while the stories generated for this minuscule
minority rested so precariously upon hope for finding a rare phenomenon—and
received such limited definition by the primitive statistical methods then available
(or, more commonly, remained unidentified by any statistical practice at all)—that
even these textbook exemplars collapsed upon restudy with proper quantitative
procedures. But consider what might have occurred, if only paleontologists had
recognized that stasis is data (I will grant some validity to the standard rationale for
regarding the second phenomenon of punctuation as an artifact of an imperfect
record). As Hallam said to me many years ago, after he had disproved the classical
story of gradualism in Gryphaea: more than 100 other species of mollusks, many
with records as rich as Gryphaea's, occur in the same Liassic rocks, yet no one
ever documented the stratigraphic history of even a single one in any study of
evolution, for all demonstrate stasis. Scientists picked out the only species that
seemed to illustrate gradualism, and even this case failed.
Despite the widespread use of proper quantitative methods today, and despite
increasing attention to the validity of stasis as an evolutionary phenomenon, this
bias still persists. I do not doubt that several species of Cenozoic planktonic
Foraminifera display gradual transitions (see pp. 803-810), but I know that these
examples have been extracted for study from a much larger potential sample of
species never documented in detail because their apparent stasis seems "boring" to
students of evolution. An eager young statistician goes to a lifelong expert and
says: I want to devote my doctoral thesis to a statistical study of evolution in a
species of foram (the most promising of major taxa, thanks to a hyper abundance
of specimens and excellent stratigraphic data in oceanic cores); which species shall
I choose? And the expert advises: why not study Graduloconoides
gradualississima; I know that this species shows interesting changes during the
upper Miocene in cores A through Z. Meanwhile, poor old boring Stasigerina
punctiphora, just as abundant in the same cores, and just as worthy of study, gets
bypassed in silence.
I find this situation particularly frustrating as paleontology's primary example
of an insidious phenomenon in science that simply has not been recognized for the
serious and distorting results perpetrated under its aegis. Most scientists do not
even recognize the problem—though some do, particularly in the medical and
social sciences, where the error has been named "publication bias," and has
inspired a small but important literature (Begg and Berlin, 1988). In publication
bias, prejudices arising from hope, cultural expectation, or the definitions of a
particular scientific theory dictate that only certain kinds of data will be viewed as
worthy of publication, or even of documentation at all. Publication bias bears no
relationship whatever with the simply immoral practice of fraud; but,
paradoxically, publication bias may exert a far more serious effect (largely because
the phenomenon must be so much