The counterattack succeeded. Rep. Hensley wrote to me on April 21, 1997: “Because of your efforts, the Bill has now been withdrawn from consideration in the House Education Committee.” Shabby and dishonest argument can win a fragile and transient advantage, but so long as we fight back, we will win. God (who, as a self-respecting deity, must honor and embrace empirical truth) really is on our side.
Punctuated equilibrium in journalism and textbooks
All scientists have read egregiously bad, hyped and distorted press commentaries about the more subtle and nuanced work of their field. I too get annoyed at such stories, but I have also learned to appreciate that most journalists take their job seriously, follow the ethics of the field, and tend to turn out good stories, on balance. When hype occurs, the fault lies just as often with scientists who simplify and over promote their work, as with reporters who [Page 991] accept what they hear too uncritically. (Journalists should check, of course, and must therefore bear part of the blame, but scientists should begin any general critique of the press with an acknowledgment of our own in camera foibles.)
The extensive press coverage of punctuated equilibrium has generally maintained adequate to high quality. Ironically, though, the most common errors — which like the old soldiers, cats and bad pennies of our mottoes, never seem to fade but turn up, however sparsely, again and again with no diminution in frequency — match the mistakes cited by creationists for utterly different purposes. If willful misuse and unintentional, albeit careless, error repeat the same false arguments, then what serves as a common source amidst such different motives (and different frequencies of occurrence, of course — pervasive for creationists, rare for reputable journalists)? Deep constraints on human mentality (common difficulties with concepts of scaling and probability, for example)? Persistent historical and cultural prejudices (about progress and gradualism, for example)? The malfeasance and hyped misleading of original authors (as our severest critics like to claim)? In any case, I am fascinated by the entire issue of commonality in errors across such a maximal range of motives, and I believe that something deep about the nature of mentality and the sociology of knowledge lies exposed therein.
Schemes of oversimplification must rank as the bete noire of journalism, at least in the eyes of scientists and other scholars. Since dichotomization stands as our primary mode of taxonomic oversimplification, probably imposed by the deep structure of the human mind, we should not be surprised that journalists have tended to treat the punctuated equilibrium debate as a dichotomous struggle between gradualists and punctuationalists, superimposed upon another false dichotomy (with supposedly perfect mapping between the two) of Darwinians (read gradualists) against anti-Darwinians (read punctuationalists). This struggle then occurs within a political dichotomy — a genuine division this time — of evolution vs. creationism. (The misappropriation of punctuated equilibrium by creationists, as documented in the last section, violates this last dichotomy and can thus be easily grasped as unfair by nearly everyone.)
The error of dichotomy appears most starkly in the minimal length and maximal hype of advertising copy for books. Pergamon's come-on for Nield and Tucker's Paleontology, for example, promises that “the approach in the evolutionary discussions is fully in line with the most recent understandings of the punctuated equilibrium/phyletic gradualism debate.” The blurb for Oliver Mayo's Natural Selection and Its Constraints proclaims: “Among other topical matters, he touches upon the controversial question of 'punctuated equilibrium' or 'phyletic gradualism' as a mechanism for major evolutionary change.”
A prominent cultural legend (with “The Emperor's New Clothes” as a prototype) celebrates the young and honest naif as exposer of an evident truth that hidebound adults will not or cannot admit. True to this scenario, the Summer 1993 publicity blurb sheet of Mount Holyoke College reports the [Page 992] happy story of Heather Winklemann, a senior who had just won a prestigious Marshall Fellowship for graduate study in England. The article focuses on her intimidating but successful oral interview, held in San Francisco. As a prospective paleontologist, the committee asked her: “Does evolution work by punctuated equilibrium? Answer yes or no?” Ms. Winklemann replied cogently by exposing the dichotomy as false — and she got her fellowship. The article ends: “'That question took me by surprise,' Winklemann recalls, 'because if you know anything about the topic you know it can't be answered with a yes or a no. Were they trying to catch me on the question? I told the committee that I couldn't give a yes-or-no answer and why.' Heather Winklemann's answer evidently was what the committee was hoping to hear.”
Beyond dichotomy, a failure to recognize the theory's proper scale stands as the most common journalistic error about punctuated equilibrium, in accounts both positive and negative. Many reporters continue to regard yearly or generational changes in populations as a crucial test for punctuated equilibrium. Thus, Keith Hindley reported the fascinating work of Peter Grant and colleagues on changes in population means for species of Darwin's Galapagos finches following widespread mortality due to extreme climatic stresses. Hindley placed the entire story in the irrelevant light of punctuated equilibrium (which cannot even “see” such transient fluctuations in population means from year to year): “Striking new evidence has refuelled the heated scientific debate about the process of evolution . . . The followers of Stephen Gould of Harvard claim that such rapid changes or 'jumps,' caused by environmental pressures, are the key to the emergence of new species... This episode has provided Gould's supporters with some of the ammunition their theory has so far lacked: good examples of sudden evolution among species alive today.”
Negative accounts of punctuated equilibrium often make the same error. In reviewing a book by Ernst Mayr in the New York Times, Princeton biologist J. L. Gould (no relation) discusses the link of punctuated equilibrium to Mayr's views on allopatric speciation. But he then attacks punctuated equilibrium because “its authors seem to believe that species-level changes can occur in one generation, presumably by the production of what the embryologist Richard Goldschmidt called 'hopeful monsters.'”
Among human foibles, our tendency to excoriate a bad job in public, but merely to smile in private at good work, imposes a marked asymmetry upon the overt reporting of relative frequencies in human conduct and intellect. In truth, although I have singled out some “howlers” for quotation in this section, most press reports of punctuated equilibrium have been accurate, while a few have been outstanding. Consequently, I close this section on punctuated equilibrium and the press with two extensive quotations from two leading science writers, one British and one American — with thanks for confirming my faith in the coherence and accessibility of the ideas and implications of punctuated equilibrium. In The Listener (magazine of the BBC) for July 19, 1986, Colin Tudge beautifully explains the key concepts and general reforms proposed by punctuated equilibrium, while also giving the critics their due: [Page 993]
A third modification of the neo-Darwinian orthodoxy is embraced in the hypothesis of punctuated equilibrium, proposed in the early 1970's by the American biologists Niles Eldredge and Stephen Jay Gould. The idea of punctuated equilibrium is not intended to dispute Darwin's central notion that the evolutionary destinies of plants and animals are shaped largely or mostly by natural selection. But it does take issue with two of his subsidiary notions: the idea that evolutionary change brought about by natural selection is necessarily gradual; and the idea that natural selection can operate only at the level of the individual.
No idea in biology has caused more contention and indeed rancor over the past 15 years. Some opponents of Gould and Eldredge argue that their observation is just plain wrong — that evolution is gradual. Some argue that even if it were true it would be trivial. And some suggest that even if it were true and not trivial, then it is in any case untestable, and therefore not worth considering.
In truth, the paleontological record sometimes seems to s
how that one form of animal may gradually turn into another, in Darwinian fashion, but often it seems to show precisely the pattern that Gould and Eldredge propose...
It's at this point that some biologists say “So what?” Who ever doubted that evolution can at times proceed more quickly than at others? Even if true (in some cases), the observation is trivial. This, however, is a severe misrepresentation of Gould and Eldredge's idea, for they are not simply making the banal observation that evolution is sometimes fast and sometimes slow. They are suggesting that the “jumps” that can be observed in the fossil record represent the emergence of new species — that is, of groups of organisms that reproduce sexually with each other but not with other groups…
Indeed, Gould and Eldredge go further than this. They suggest that when a species divides to form several new species, this is analogous to the birth of new individuals; and just as natural selection tends to weed out weak individuals in favor of the strong, so it serves to weed out new experimental species. Thus, they suggest, natural selection can operate at the level of the species (“species selection”) and not simply at the level of the individual, as Darwin proposed. This is not a trivial observation....
The attacks on punctuated equilibrium seem powerful. But Gould gives as good as he gets, and my own betting is that the theory of punctuated equilibrium, with a bit more buffering from biologists at large, will take its place as an important modification of Darwin's basic ideas.
In an article on Peter Sheldon's claims for extensive gradualism in trilobites, and therefore generally critical of punctuated equilibrium, James Gleick states that our theory has provoked “the most passionate debate in evolutionary theory over the last decade,” and then provides a fine summary of our key ideas, and of the intellectual depth of the resulting debate (New York Times, December 22, 1987): [Page 994]
Steady flow or fits and starts — the division between these conceptions of evolution has dominated the debate over evolutionary theory. The punctuated equilibrium model has stimulated much research and drawn many adherents. Some of its central notions have taken firm hold.
Even the most traditional Darwinians, for example, acknowledge that punctuated equilibrium has become an important part of the picture of evolution. Some species do little of evolutionary interest for millions of years at a time. ...
But the debate continues to rage, because it concerns far more than speed itself. At stake are the fundamental questions of evolution: when and why does a creature change from one form to another? Is most evolution the slow, unceasing accumulation of the small changes a geneticist sees in laboratory fruit flies, or does it occur in episodes, when a small population, perhaps isolated geographically, suddenly changes enough to give rise to a new species?
Suddenly, in paleontological terms, can mean hundreds of thousands of years . . . Proponents of punctuated equilibrium take pains to stress that such events rely mainly on the Darwinian principles of natural selection among individuals varying randomly from one another. Even so, to some biologists, punctuated equilibrium seems like a resort to some process apart from the usual rules — “mutations that appear to be magic,” Dr. Maynard Smith said.
“They have argued that their results mean that evolution as seen on the large scale is not just the summing up of small events,” he said, “but a series of quite special things that people like me” — population geneticists — “don't see. We don't want to be written out of the script.”
The movement of scientific ideas into textbooks may provide our best insight into social forces that direct the passage from maximal professional independence into the most conservative of print genres. To be successful, textbooks must sell large numbers of copies to audiences highly constrained by set curricula, teachers who hesitate to revise courses and lessons substantially, and conservative communities that shun scholastic novelty. These external reasons reinforce the internal propensities of publishers who are happy to jazz up or dumb down, but not to innovate, and authors who experience great pressure to follow the conventions of textbook cloning, and not to depart from the standard takes, examples, illustrations, and sequences. Did you ever see a high school biology textbook that doesn't start the evolution chapter with Lamarck's errors, Darwin's truths, and giraffes' necks in that order?
In this context, I delight in the rapid passage of punctuated equilibrium from professional debate to nearly obligatory treatment in the evolution chapter of biology textbooks. I could put a cynical spin on this phenomenon, but prefer an interpretation, in my admittedly partisan manner, based on the successful ontogeny of punctuated equilibrium from a controversial idea to a firm item of natural knowledge, however undecided the issues of relative frequency and importance remain. [Page 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 [Page 996] our worst mental habit of interpreting other ranges of size, or other domains of time, in our own limited terms.
> For example, Mettler, Gregg, and Schaffer's textbook on Population Genetics and Evolution (1988, p. 304) states: “The punctuated equilibrium theory, on the other hand, holds that sudden appearance is due to rapid selection, rather than rapid spread, and that stasis results because evolutionary change occurs in large discrete jumps rather than by a series of gene substitutions. There really are no gradual changes or intermediate stages.” In their volume on Sexual Selection for the prestigious Scientific American series (1989, p. 83), Gould and Gould (no relation) write: “The proven ability of selection to operate quickly in at least some cases, has led to the widely publicized theory of punctuated evolution. According to the original version, no intermediate forms are preserved simply because there are no halfway creatures in the first place: new species come into being in single steps.”
The Structure of Evolutionary Theory Page 158
