Punctuated Equilibrium and the Validation of Macroevolutionary Theory 995
But I am also not surprised that textbooks encourage promulgation of standard
errors—a tendency arising from pressures to simplify ideas, downplay controversy,
favor bland consensus, and generate a fairly uniform treatment from text to text. We
often encounter, for example, the same oversimplification by dichotomy that
compromises so many press reports. Villee and collaborators (1989) state, for
example: "Some scientists believe that evolution is a gradual process, while others
think evolution occurs in a series of rapid changes." The headings of entire sections
often bear this burden, as in Tamarin's (1986) title for his pages on evolutionary rates:
"Phyletic Gradualism Versus Punctuated Equilibrium."
However, the bland consensus favored by textbooks (and euphemistically called
"balance") often imposes a peculiar resolution foreign to most journalistic accounts,
where controversy tends to be exaggerated rather than defanged to a weak and
toothless smile of agreement at a meaningless center. Textbooks therefore tend to
present the dichotomy and then to state that "I am right and you are right and
everything is quite correct," to quote Pish-Tush in The Mikado—as average reality
rests upon the blandest version of a meaningless golden mean. The 1996 edition of J.
L. Gould and W. T. Keeton proclaims (p. 511) that "the usual tempo of speciation
probably lies somewhere between the gradual-change and the punctuated equilibrium
models." (But such a various phenomenon as speciation has no "usual tempo," or any
single meaningful measure of central tendency at all. Blandness, in this case, reduces
to incoherence.)
In another example, Levin (1991, p. 112) concludes with pure textbook
boilerplate that could be glued over almost any scientific controversy: "The final
chapter on the question of punctuated evolution versus phyletic gradualism has not
been written. At present, the proponents of punctuated evolution appear to be more
numerous than those of phyletic gradualism. Like most controversies in science,
however, the answer need not lie totally in one camp, and it is evident that instances
of phyletic gradualism can also be recognized in the fossil record of certain groups of
plants and animals."
If we consider dichotomy as a general mental error of oversimplified
organizational logic, then the most common scientific fallacy in textbook accounts of
punctuated equilibrium resides, once again, in false scaling by application of the
theory to levels either below or above the appropriate subject of speciation in
geological time. As before, the conflation of punctuated equilibrium (speciation in
geological moments) with true saltation (speciation in a single generation, or moment
of human perception) persists as the greatest of all scaling errors. I am discouraged by
this error for three basic reasons: (1) It has been exposed and explained so many
times, both by the authors of punctuated equilibrium and by many others; so
continued propagation can only record carelessness. (2) Saltation at any appreciable
relative frequency surely represents a false theory; so punctuated equilibrium
becomes tied to a patently erroneous idea; whereas misapplication of punctuated
equilibrium to higher levels may at least misassociate the name with a true
phenomenon (like catastrophic mass extinction). (3) This particular error of scaling
embodies