One could argue, I suppose, that these instances of conservation only record adaptation, unchanged through all of life’s vicissitudes because their optimality can’t be improved. But most biologists feel that such stability acts primarily as a constraint upon the range and potentiality of adaptation, for if organisms of such different function and ecology must build bodies along the same basic pathways, then limitation of possibilities rather than adaptive honing to perfection becomes a dominant theme in evolution. At a minimum, in explaining evolutionary pathways through time, the constraints imposed by history rise to equal prominence with the immediate advantages of adaptation.
My own field of paleontology has strongly challenged the Darwinian premise that life’s major transformations can be explained by adding up, through the immensity of geological time, the successive tiny changes produced generation after generation by natural selection. The extended stability of most species, and the branching off of new species in geological moments (however slow by the irrelevant scale of a human life)—the pattern known as punctuated equilibrium—requires that long-term evolutionary trends be explained as the distinctive success of some species versus others, and not as a gradual accumulation of adaptations generated by organisms within a continuously evolving population. A trend may be set by high rates of branching in certain species within a larger group. But individual organisms do not branch; only populations do—and the causes of a population’s branching can rarely be reduced to the adaptive improvement of its individuals.
The study of mass extinction has also disturbed the ultra-Darwinian consensus. We now know, at least for the terminal Cretaceous event some 65 million years ago that wiped out dinosaurs along with about 50 percent of marine invertebrate species, that some episodes of mass extinction are both truly catastrophic and set off by extraterrestrial impact. The death of some groups (like dinosaurs) in mass extinctions and the survival of others (like mammals), while surely not random, probably bears little relationship to the evolved, adaptive reasons for success of lineages in normal Darwinian times dominated by competition. Perhaps mammals survived (and humans ultimately evolved) because small creatures are more resistant to catastrophic extinction. And perhaps Cretaceous mammals were small primarily because they could not compete successfully in the larger size ranges of dominant dinosaurs. Immediate adaptation may bear no relationship to success over immensely long periods of geological change.
Why then should Darwinian fundamentalism be expressing itself so stridently when most evolutionary biologists have become more pluralistic in the light of these new discoveries and theories? I am no psychologist, but I suppose that the devotees of any superficially attractive cult must dig in when a general threat arises. “That old time religion; it’s good enough for me.” There is something immensely beguiling about strict adaptationism—the dream of an underpinning simplicity for an enormously complex and various world. If evolution were powered by a single force producing one kind of result, and if life’s long and messy history could therefore be explained by extending small and orderly increments of adaptation through the immensity of geological time, then an explanatory simplicity might descend upon evolution’s overt richness. Evolution then might become “algorithmic,” a surefire logical procedure, as in Daniel Dennett’s reverie. But what is wrong with messy richness, so long as we can construct an equally rich texture of satisfying explanation?
Daniel Dennett’s 1995 book, Darwin’s Dangerous Idea, presents itself as the ultras’ philosophical manifesto of pure adaptationism. Dennett explains the strict adaptationist view well enough, but he defends a miserly and blinkered picture of evolution in assuming that all important phenomena can be explained thereby. His limited and superficial book reads like a caricature of a caricature—for if Richard Dawkins has trivialized Darwin’s richness by adhering to the strictest form of adaptationist argument in a maximally reductionist mode, then Dennett, as Dawkins’s publicist, manages to convert an already vitiated and improbable account into an even more simplistic and uncompromising doctrine. If history, as often noted, replays grandeurs as farces, and if T.H. Huxley truly acted as “Darwin’s bulldog,” then it is hard to resist thinking of Dennett, in this book, as “Dawkins’s lapdog.”
Dennett bases his argument on three images or metaphors, all sharing the common error of assuming that conventional natural selection, working in the adaptationist mode, can account for all evolution by extension—so that the entire history of life becomes one grand solution to problems in design. “Biology is engineering,” Dennett tells us again and again. In a devastating review, published in the leading professional journal Evolution, and titled “Dennett’s Dangerous Idea,” H. Allen Orr notes:
His review of attempts by biologists to circumscribe the role of natural selection borders on a zealous defense of panselectionism. It is also absurdly unfair…. Dennett fundamentally misunderstands biologists’ worries about adaptationism. Evolutionists are essentially unanimous that—where there is “intelligent Design”—it is caused by natural selection…. Our problem is that, in many adaptive stories, the protagonist does not show dead-obvious signs of Design.
In his first metaphor, Dennett describes Darwin’s dangerous idea of natural selection as a “universal acid”—to honor both its ubiquity and its power to corrode traditional Western beliefs. Speaking of adaptation, natural selection’s main consequence, Dennett writes: “It plays a crucial role in the analysis of every biological event at every scale from the creation of the first self-replicating macromolecule on up.” I certainly accept the acidic designation—for the power and influence of the idea of natural selection does lie in its radical philosophical content—but few biologists would defend the blithe claim for ubiquity. If Dennett chooses to restrict his personal interest to the engineering side of biology—the part that natural selection does construct—then he is welcome to do so. But he may not impose this limitation upon others, who know that the record of life contains many more evolutionary things than are dreamt of in Dennett’s philosophy.
Natural selection does not explain why many evolutionary transitions from one nucleotide to another are neutral, and therefore nonadaptive. Natural selection does not explain why a meteor crashed into the earth 65 million years ago, setting in motion the extinction of half the world’s species. As Orr points out, Dennett’s disabling parochialism lies most clearly exposed in his failure to discuss the neutral theory of molecular evolution, or even to mention the name of its founder, the great Japanese geneticist Motoo Kimura—for few evolutionary biologists would deny that this theory ranks among the most interesting and powerful adjuncts to evolutionary explanation since Darwin’s formulation of natural selection. You don’t have to like the idea, but how can you possibly leave it out?
In a second metaphor, Dennett continually invokes an image of cranes and skyhooks. In his reductionist account of evolution, cranes build the good design of organisms upward from nature’s physicochemical substrate. Cranes are good. Natural selection is evolution’s basic crane; all other cranes (sexual reproduction, for example) act as mere auxiliaries to boost the speed or power of natural selection in constructing organisms of good design. Skyhooks, on the other hand, are spurious forms of special pleading that reach down from the numinous heavens and try to build organic complexity with ad hoc fallacies and speculations unlinked to other proven causes. Skyhooks, of course, are bad. Everything that isn’t natural selection, or an aid to the operation of natural selection, is a skyhook.
If you think that I am being simplistic or unfair to Dennett in this characterization, read his book and see if you can detect anything more substantial in this metaphor. I could only find a rhetorical stick for beating pluralists into line. Can’t Dennett see that a third (and correct) option exists to his oddly dichotomous Hobson’s choice: either accept the idea of one basic crane with auxiliaries, or believe in skyhooks. May I suggest that the platform of evolutionary explanation houses an assortment of basic cranes, all helping to build the edifice of life’s history in its full grandeur (not only the architecture of well-engineered organisms). Natural selection may be the biggest crane with the largest set of auxiliaries, but Kimura’s theory of neutralism is also a crane; so is punctuated equilibrium; so is the channelling of evolutionary change by developmental constraints. “In my father’s house are many mansions”—and you need a lot of cranes to build something so splendid and variegated.
For his third metaphor—though he would demur and falsely label the claim as a fundamental statement about causes—Dennett describes evolution as an “algorithmic process.” Algorithms are abstract rules of calculation, and fully general in making no reference to particular content. In Dennett’s words: “An algorithm is a certain sort of formal process that can be counted on—logically—to yield a certain sort of result whenever it is ‘run’ or instantiated.” If evolution truly works by an algorithm, then all else in Dennett’s simplistic system follows: we need only one kind of crane to supply the universal acid.
I am perfectly happy to allow—indeed I do not see how anyone could deny—that natural selection, operating by its bare-bones mechanics, is algorithmic: variation proposes and selection disposes. So if natural selection builds all of evolution, without the interposition of auxiliary processes or intermediary complexities, then I suppose that evolution is algorithmic too. But—and here we encounter Dennett’s disabling error once again—evolution includes so much more than natural selection that it cannot be algorithmic in Dennett’s simple calculational sense.
Yet Dennett yearns to subsume all the phenomenology of nature under the limited aegis of adaptation as an algorithmic result of natural selection. He writes: “Here, then, is Darwin’s dangerous idea: the algorithmic level is the level that best accounts for the speed of the antelope, the wing of the eagle, the shape of the orchid, the diversity of species, and all the other occasions for wonder in the world of nature” (Dennett’s italics). I will grant the antelope’s run, the eagle’s wing, and much of the orchid’s shape—for these are adaptations, produced by natural selection, and therefore legitimately in the algorithmic domain. But can Dennett really believe his own imperialistic extensions? Is the diversity of species no more than a calculational consequence of natural selection? Can anyone really believe, beyond the hype of rhetoric, that “all the other occasions for wonder in the world of nature” flow from adaptation?
Perhaps Dennett only gets excited when he can observe adaptive design, the legitimate algorithmic domain; but such an attitude surely represents a blinkered view of nature’s potential interest. I regard the neutral substitution of nucleotides as an “occasion for wonder in the world of nature.” And Imarvel at the probability that the impact of a meteor wiped out dinosaurs and gave mammals a chance. If this contingent event had not occurred, and imparted a distinctive pattern to the evolution of life, we would not be here to wonder about anything at all!
“Straight is the gate, and narrow is the way.” Fundamentalists of all stripes live by this venerable motto, and must therefore wield their unsleeping swords in constant mental fight against contrary opinions of apostates and opponents (who usually make up a sizable majority—for, as Jesus also noted, “Wide is the gate, and broad is the way, that leadeth to destruction”). The favored fate for the nonelect varies, according to the temperament and power of true believers, from the kindness of simple pity to the refiner’s fire of extirpation. But the basic ideological weapon of fundamentalism rarely departs much from the tried and true techniques of anathematization.
Unfortunately, at least for the ideals of intellectual discourse, anathematization rarely follows the dictates of logic or evidence, and nearly always scores distressingly high in heat/light ratio. Anathema also requires an anathemee—and I seem to have been elected. (Whatever my professional contributions to proper Darwinian pluralism, I stand convicted, Isuggest, primarily for my efforts to bring the full scope of technical debate, with all its complexities and messiness, but without loss of substance, to general readers.)
Personal attack generally deserves silence by way of response. But as two old troupers (Noam Chomsky and Salvador Luria) once advised me in my only comparable earlier incident, an exception must be made in one and only one circumstance: when denigrators float a demonstrably false charge that, if unanswered, may acquire a “life of its own.” A false fact can be refuted, a false argument exposed; but how can one respond to a purely ad hominem attack? This harder, and altogether more discouraging, task may best be achieved by exposing internal inconsistency and unfairness of rhetoric.
John Maynard Smith, Emeritus Professor at Sussex and dean of British ultra-Darwinians, reviewed Dennett’s book in this publication—thus providing small prospect for critical commentary. Maynard Smith began his supposed analysis of ultraDarwinian criticism with the following gratuitous remark:
Gould occupies a rather curious position, particularly on his side of the Atlantic. Because of the excellence of his essays, he has come to be seen by non-biologists as the preeminent evolutionary theorist. In contrast, the evolutionary biologists with whom I have discussed his work tend to see him as a man whose ideas are so confused as to be hardly worth bothering with, but as one who should not be publicly criticized because he is at least on our side against the creationists.3
It seems futile to reply to an attack so empty of content, and based only on comments by anonymous critics; if they were named, they would, Isuspect, turn out to be a very small circle of true believers. And if I may beg the editor’s indulgence for one emotional outburst, may I say, at least, that I resent Maynard Smith’s pompous offer of grudging acceptance for my utility in fighting creationism. I did not do so to win entry into his circle of genuine professionals (for I think that we both hold honored union cards therein), but rather as a member of the larger scientific community, and as a small contribution to the continual struggle of people who cherish rationality. We will not win this most important of all battles if we descend to the same tactics of backbiting and anathematization that characterize our true opponents.
Instead of responding to Maynard Smith’s attack against my integrity and scholarship, citing people unknown and with arguments unmentioned, let me, instead, merely remind him of the blatant inconsistency between his admirable past and lamentable present. Some sixteen years ago he wrote a highly critical but wonderfully supportive review of my early book of essays, The Panda’s Thumb, stating: “I hope it will be obvious that my wish to argue with Gould is a compliment, not a criticism.”4 He then attended my series of Tanner Lectures at Cambridge in 1984 and wrote in a report for Nature, and under the remarkable title “Paleontology at the High Table,” the kindest and most supportive critical commentary I have ever received. He argued that the work of a small group of American paleobiologists had brought the entire subject back to theoretical centrality within the evolutionary sciences.
The attitude of population geneticists to any palaeontologist rash enough to offer a contribution to evolutionary theory has been to tell him to go away and find another fossil, and not to bother the grownups.
In the last ten years, however, this situation has changed by the work of a group of palaeontologists, of whom Gould has been a leading figure.
He ended the article with a quintessential Oxbridge metaphor: “The Tanner lectures were an entertaining and stimulating occasion. The palaeontologists have too long been missing from the high table. Welcome back.”
Maynard Smith then republished both papers (along with two others that cast my work in the central role of a section entitled “Did Darwin Get it Right?”) in his 1988 volume of essays, Did Darwin Get it Right? Essays on Games, Sex and Evolution. Most remarkably of all, he then reviewed two books on dinosaurs for this journal and devoted more than half his space (much to the distress, I am sure, of the authors of the books supposedly under review) to a trenchant critique of my views on adaptation. He began by writing: “When, as often happens, I find myself dissenting from something written by Stephen Jay Gould, I remind myself that we share a common childhood experience. We were both dinosaur nuts.” And he ended with an apology: “I fear that what started out as a review of two books about dinosaurs has wandered off into a discussion of the functional and adaptationist approaches to anatomy.”5
So we face the enigma of a man who has written numerous articles, amounting to tens of thousands of words, about my work—always strongly and incisively critical, always richly informed (and always, I might add, enormously appreciated by me). But now Maynard Smith needs to canvass unnamed colleagues to find out that my ideas are “hardly worth bothering with.” He really ought to be asking himself why he has been bothering about my work so intensely, and for so many years. Why this dramatic change? Has he been caught up in apocalyptic ultra-Darwinian fervor? I am, in any case, saddened that his once genuinely impressive critical abilities seem to have become submerged within the simplistic dogmatism epitomized by Darwin’s Dangerous Idea, a dogmatism that threatens to compromise the true complexity, subtlety (and beauty) of evolutionary theory and the explanation of life’s history. I shall examine this Darwinian fundamentalism further in a second, and concluding, article in the next issue.
The New York Review, November 30, 1995.↩
London Review of Books, September 17-30, 1981.↩
The New York Review, April 25, 1991.↩
Evolutionary Psychology: An Exchange October 9, 1997