The Structure of Evolutionary Theory Page 9

  I must also confess to some preconditioning beyond punctuated equilib­rium. I had admired Wynne-Edwards's pluck (1962) from the start, even though I agreed with Williams's (1966) trenchant criticisms of his particular defenses for group selection, rooted in the ability of populations to regulate their own numbers in the interests of group advantage. Still, I felt, for no rea­son beyond vague intuition, that group selection made logical sense and might well find other domains and formulations of greater validity — a feeling that has now been cashed out by modern reformulations of evolutionary the­ory (see especially Wilson and Sober, 1998, and Chapters 8 and 9 herein).

  My odyssey on the second branch of balancing internal constraint with external adaptation in understanding the patterning and creative population of novel places in evolutionary morphospace followed a much more com­plex, meandering and diverse set of pathways. As an undergraduate, I loved D'Arcy Thompson's Growth and Form (1917; see Gould, 1971b, for my first “literary” paper), and wrote a senior thesis on his theory of morphology. But I thought that I admired the book only for its incomparable prose, and I at­tacked the anti-Darwinian (and structuralist) components of his theory un­mercifully. I then took up allometry for my first empirical studies, somehow fascinated by structural constraint and correlation of growth, but thinking all the while that my task must center on a restoration of adaptationist themes to this “holdout” bastion of formalist thought — particularly the achievement of biomechanical optima consistent with the Galilean principle of decreasing surface/volume ratios with increasing size in isometric forms. I remain proud of my first review article, dedicated to this subject (Gould, 1966), written when I was still a graduate student, but I am now embarrassed by the fervor of my adaptationist convictions.

  I emphasized allometric analysis, now in a directly multivariate reformulation, in my first set of empirical studies on the Bermudian pulmonate snail Poecilozonites (see especially Gould, 1969 — the published version of my Ph.D. dissertation). And yet, of all the long and largely adaptationist treatises in this series, and for some reason that I could not identify at the time, the conclusion that I reached with most satisfaction, and that I somehow re­garded as most theoretically innovative (without knowing why), resided in a short, and otherwise insignificant, article that I wrote for a specialized pale-ontological journal on a case of convergence produced by structural necessity, given modes of coiling and allometry in this genus, rather than by selectionist honing (for some cases rested upon ecophenotypic expression, others on paedomorphosis, and still others on gradual change that could be read as conventionally adaptive): “Precise but fortuitous convergence in Pleistocene land snails” (Gould, 1971c).

  Five disparate reasons underlie my more explicit recognition, during the 1970's and early 1980's, of the importance and theoretical interest (and [Page 43] iconoclasm versus Darwinian traditions) of nonadaptationist themes rooted in structural and historical constraint. First, I stood under the dome of San Marco during a meeting in Venice and then wrote a notorious paper with Dick Lewontin on the subject of spandrels, or nonadaptive sequelae of prior structural decisions (Gould and Lewontin, 1979 — see Chapter 11, pp. 1246–1258). Second, I recognized, with Elisabeth Vrba, that the lexicon of evolu­tionary biology possessed no term for the evidently important phenomenon of structures coopted for utility from different sources of origin (including nonadaptive spandrels), and not directly built as adaptations for their cur­rent function. We therefore devised the term “exaptation” (Gould and Vrba, 1982) and explored its implications for structuralist revisions to pure Dar­winian functionalism. Third, I worked with a group of paleontological colleagues (Raup et al, 1973; Raup and Gould, 1974; Gould et al., 1977) to develop more rigorous criteria for identifying the signals that required selec­tionist, rather than stochastic, explanation of apparent order in phyletic pat­terns. This work left me humbled by the insight that our brains seek pattern, while our cultures favor particular kinds of stories for explaining these pat­terns — thus imposing a powerful bias for ascribing conventional determinis­tic causes, particularly adaptationist scenarios in our Darwinian traditions, to patterns well within the range of expected outcomes in purely stochastic sys­tems. This work sobered me against such a priori preferences for adaptation­ist solutions, so often based upon plausible stories about results, rather than rigorous documentation of mechanisms.

  Fourth, and most importantly, I read the great European structuralist literatures in writing my book on Ontogeny and Phylogeny (Gould, 1977b). I don't see how anyone could read, from Goethe and Geoffroy down through Severtzov, Remane and Riedl, without developing some appreciation for the plausibility, or at least for the sheer intellectual power, of morphological ex­planations outside the domain of Darwinian functionalism — although my resulting book, for the last time in my career, stuck closely to selectionist or­thodoxy, while describing these alternatives in an accurate and sympathetic manner. Fifth, my growing unhappiness with the speculative character of many adaptationist scenarios increased when, starting in the mid 1970's, the growing vernacular (and some of the technical) literature on sociobiology touted conclusions that struck me as implausible, and that also (in some cases) ran counter to my political and social beliefs as well.

  Personal distaste, needless to say, bears no necessary relationship to scien­tific validity. After all, what could be more unpleasant, but also more fac­tually undeniable, than personal mortality? But when distasteful conclusions gain popularity by appealing to supposedly scientific support, and when this “support” rests upon little more than favored speculation in an orthodox mode of increasingly dubious status, then popular misuse can legitimately sharpen a scientist's sense of unhappiness with the flawed theoretical basis be­hind a particular misuse. In any case, I trust that this compendium of reasons will dispel Cain's (1979) hurtful assertion that Lewontin, I, and other evolu­tionists who questioned early forms of sociobiology by developing a general [Page 44] critique of adaptationism, had acted cynically, and even anti-scientifically, in opposing biological theories that we knew to be true because we disliked their political implications for explaining human behavior. My own growing doubts about adaptationism arose from several roots, mostly paleontological, with any displeasure about sociobiology serving as a late and minor spur to further examination and synthesis.

  I then tried to apply my general critique of pure Darwinian functionalism, and my conviction that important and positive constraints could be actively identified by quantitative morphometric study (and not merely passively in­ferred from failures of adaptationist scenarios) in my work on “covariance sets” in the growth, variation, and evolution of the West Indian pulmonate Cerion (Gould, 1984b and c), a snail that encompasses its maximal diver­sity in overt form among populations within a constraining set of pervasive allometries in growth. I discuss some of this work in my text on the empirical validation of positive constraint (see Chapter 10, pages 1045–1051).

  My doubts on the third branch of extrapolationism and uniformity began even earlier, and in a more inchoate way, but then gained expression in my ef­forts in the history of science, and not so much in my direct empirical work — hence, in part, the reduced attention devoted to this theme (Chapters 6 and 12) compared with the first two branches of selection's agency and efficacy. On a fieldtrip in my freshman geology course, my professor took us to a trav­ertine mound and argued that the deposit must be about 11,000 years old because he had measured the current rate of accumulation and then extrapo­lated back to a beginning. When I asked how he could assume such con­stancy of rate, he replied that the fundamental rule of geological inference, something called “the principle of uniformitarianism” permitted such infer­ences because we must regard the laws of nature as constant if we wish to reach any scientific conclusions about the past. This argument struck me as logically incorrect, and I pledged myself to making a rigorous analysis of the reasons.

  As a joint major in geology and philosophy, I studied th
is issue throughout my undergraduate years, producing a paper entitled “Hume and uniform­itarianism” that eventually transmogrified into my first publication (Gould, 1965), “Is uniformitarianism necessary?” (Norman Newell, my graduate ad­visor, urged me to send the paper to Science where, as I learned to my amuse­ment much later, my future “boss” at Harvard, the senior paleontology pro­fessor Bernie Kummel, rejected it roundly as a reviewer. Properly humbled — although I still regard his reasons as ill founded — I then sent the paper to a specialty journal in geology.)

  May I share one shameful memory of this otherwise iconoclastic first paper, from which I still draw some pride? In my undergraduate work on this theme, I made a personal discovery (as others did independently) that became impor­tant in late 20th-century studies of the history of geology. I had been schooled in the conventional view that the catastrophists (aka “bad guys”) had in­voked supernatural sources of paroxysmal dynamics in order to compress the earth's history into the strictures of biblical chronology. I read and reread all [Page 45] the classical texts of late 18th and early 19th century catastrophism in their original languages — and I could find no claim for supernatural influences upon the history of the earth. In fact, the catastrophists seemed to be advanc­ing the opposite claim that we should base our causal conclusions upon a lit­eral reading of the empirical record, whereas the uniformitarians (aka “good guys”) seemed to be arguing, in an opposing claim less congenial with the ste­reotypical empiricism of science, that we must make hypothetical inferences about the gradualistic mechanics that a woefully imperfect record does not permit us to observe directly.

  But, although I had developed and presented an iconoclastic exegesis of Lyell, I simply lacked the courage to state so general a claim for inverting the standard view about uniformitarians and catastrophists. I assumed that I must be wrong, and that I must have misunderstood catastrophism because I had not read enough, or could not comprehend the subtleties at this fledgling state of a career. So I scoured the catastrophist literature again until I found a quote from William Buckland (both a leading divine and the first reader in ge­ology at Oxford) that could be interpreted as a defense of supernaturalism. I cited the quotation (Gould, 1965, p. 223) and stuck to convention on this broader issue, while presenting an original analysis of multiple meanings — some valid (like the invariance of law) and some invalid (like my professor's claim for constancy in range of rates) — subsumed by Lyell under the singular description of “uniformity” in nature.

  This work led me, partly from shame at my initial cowardice, and as others reassessed the scientific character of catastrophism, to a more general analysis of the potential validity of catastrophic claims, and particularly to an under­standing of how assumptions of gradualism had so stymied and constrained our comprehension of the earth's much richer history. These ideas forced me to question the necessary basis for Darwin's key assumption that observable, small-scale processes of microevolution could, by extension through the im­mensity of geological time, explain all patterns in the history of life — namely, the Lyellian belief in uniformity of rate (one of the invalid meanings of the hy­brid concept of uniformitarianism). This exegesis led to a technical book about concepts of time and direction in geology (Gould, 1987b), to an en­larged view that encouraged the development of punctuated equilibrium, and to a position of cautious favor towards such truly catastrophic proposals as the Alvarez theory of mass extinction by extraterrestrial impact — a concept ridiculed by nearly all other paleontologists when first proposed (Alvarez et a., 1980), but now affirmed for the K-T event, and accepted as an empirical basis for expanding our range of scientifically legitimate hypotheses beyond the smooth extrapolationism demanded by this third branch of Darwinian central logic.

  In addition to these disparate accretions of revisionism on the three branches of Darwinian central logic, one further domain — my studies in the history of evolutionary thought — served as a sine qua поп for wresting a co­herent critique from such an inchoate jumble of disparate items. Above all, if I had not studied Darwin's persona and social context so intensely, I doubt [Page 46] that I would ever have understood the motivations and consistencies — also the idiosyncrasies of time, place and manner — behind the abstract grandeur of his view of life. History, as I argued before (see p. 35), must not be dis­missed as a humanistic frill upon the adamantine solidity of “real” science, but must be embraced as the coordinating context for any broad view of the logic and reasoning behind a subject so close to the bone of human concern as the science of life's nature and structure. (Of the two greatest revolutions in scientific thought, Darwin surely trumps Copernicus in raw emotional im­pact, if only because the older transition spoke mainly of real estate, and the later of essence.)

  Some of my historical writing appeared in the standard professional litera­ture, particularly my thesis about the “hardening” of the Modern Synthesis (Gould, 1980e, 1982a, 1983b), a trend (but also, in part, a drift) towards a stricter and less pluralistic Darwinism. Several full-time historians of science then affirmed this hypothesis (Provine, 1986; Beatty, 1988; Smocovitis, 1996). But much of the historical analysis behind the basic argument of this book had its roots (in my consciousness at least) in the 300 consecutive monthly essays that I wrote from 1974 to 2001 in the popular forum of Nat­ural History magazine, where I tried to develop a distinctive style of “mini in­tellectual biography” in essay form — attempts to epitomize the key ideas of a professional career in a biographic context, and within the strictures of a few thousand words. By thus forcing myself to emphasize essentials and to discard peripherals (while always searching out the truly lovely details that best exemplify any abstraction), I think that I came to understand the ma­jor ideological contrasts between the defining features of Darwinian theory and the centerpieces of alternative views. In this format, I first studied such structuralist alternatives as Goethe's theory of the archetypal leaf, Geoffroy's hypothesis on the vertebral underpinning of all animals, and on dorsoventral inversion of arthropods and vertebrates, and Owen's uncharacteristic English support for this continental view of life. I also developed immense sympathy for the beauty and raw intellectual power of various alternatives, even if I eventually found them wanting in empirical terms. And I came to understand the partial validity, and even the moral suasion, in certain proposals unfairly ridiculed by history's later victors — as in reconsidering the great hippocam­pus debate between Huxley and Owen, and recognizing how Owen used his (ultimately false) view in the service of racial egalitarianism, while Huxley misused his (ultimately correct) interpretation in a fallacious defense of tradi­tional racial ranking.

  Finally, my general love of history in the broadest sense spilled over into my empirical work as I began to explore the role of history's great theoretical theme in my empirical work as well — contingency, or the tendency of com­plex systems with substantial stochastic components, and intricate nonlinear interactions among components, to be unpredictable in principle from full knowledge of antecedent conditions, but fully explainable after time's actual unfoldings. This work led to two books on the pageant of life's history (Gould, 1989c; Gould, 1996a). Although this book, by contrast, treats [Page 47] general theory and its broad results (pattern vs. pageant in the terms of this text), rather than contingency and the explanation of life's particulars, the science of contingency must ultimately be integrated with the more conventional sci­ence of general theory as explored in this book — for we shall thus attain our best possible understanding of both pattern and pageant, and their different attributes and predictabilities. The closing section of the book (pp. 1332–1343 of Chapter 12) offers some suggestions for these future efforts.

  When I ask myself how all these disparate thoughts and items fell together into the one long argument of this book, I can only cite — and I don't know how else to put this — my love of Darwin and the power of his genius. Only he could have presented such a fecund framework of a fully consistent
theory, so radical in form, so complete in logic, and so expansive in implication. No other early evolutionary thinker ever developed such a rich and comprehen­sive starting point. From this inception, I only had to explicate the full origi­nal version, tease out the central elements and commitments, and discuss the subsequent history of debate and revision for these essential features, culmi­nating in a consistent reformulation of the full corpus in a helpful way that leaves Darwin's foundation intact while constructing a larger edifice of in­terestingly different form thereupon. Clearly I do not honor Darwin by hagiography, if only because such obsequious efforts would make any honest character cringe (and would surely cause Darwin to spin in his grave, thus up­setting both the tourists in Westminster Abbey and the adjacent bones of Isaac Newton). I honor Darwin's struggles as much as his successes, and I fo­cus on his few weaknesses as entry points for needed revision — his acknowledged failure to solve the “problem of diversity,” or his special pleading for progress in the absence of any explicit rationale from the operation of his central mechanism of natural selection.

  As a final comment, if this section has violated the norms of scientific discourse (at least in our contemporary world, although not in Darwin's age) by the liberty that I have taken in explicating personal motives, errors and cor­rections, at least I have shown how we all grope upward from initial stupid­ity, and how we would never be able to climb without the help and collabora­tion of innumerable colleagues, all engaged in the intensely social enterprise called modern science. I experienced no eureka moment in developing the long argument of this book. I forged the chain link by link, from initial pos­session of a few separate items that I didn't even appreciate as pieces of a sin­gle chain, or of any chain at all. I made my linkages one by one, and then of­ten cut the segments apart, in order to refashion the totality in a different order. So many people helped me along the way — from long dead antecedents by their wise words to younger colleagues by their wisecracks — that I must view this outcome as a social project, even though I, the most arrogant of lite­rati, insisted on writing every word. Perhaps I can best express my profound thanks to the members of such an intellectual collectivity by stating, in the most literal sense, that this book would not exist without their aid and sufferance. My formal dedication to my two dearest and closest paleontological collaborators in this effort to formulate macroevolutionary theory records [Page 48] the worthy apex of an extensive pyramid. Scientists fight and squabble as all folks do (and I have scarcely avoided a substantial documentation thereof in this book). But we are, in general, a reasonably honorable lot, and we do em­brace a tendency to help each other because we really do revel in the under­standing of nature's facts and ways — and most of us will even trade some per­sonal acclaim for the goal of faster and firmer learning. For all the tensions and unhappinesses in any life, I can at least say, with all my heart, that I chose to work in the best of all enterprises at the best of all possible times. May our contingent future only improve this matrix for my successors.