The Structure of Evolutionary Theory

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The Structure of Evolutionary Theory Page 154

by Stephen Jay Gould


  In an obviously imagistic metaphor with no causal meaning, Thurow identifies the five “economic tectonic plates” that will incite the next punctuation by crunching and grinding as their rigid borders crash: “the end of commu­nism,” “the technological shift to an era dominated by man-made brain­power industries,” “a demography never before seen” (increasing average age, greater movement of populations to cities, etc.), “a global economy,” and “an era where there is no dominant economic, political or military power” (pp. 8-9).

  But his invocation of punctuated equilibrium shows more structural and causal connection to the “parent” phenomenon from the natural sciences. Thurow (p. 7) notes both the long plateaus and the tendency for rapid histori­cal shifts in transitions between macroeconomic systems that organize entire societies:

  Periods of punctuated equilibrium are equally visible in human history. Although they came almost two thousand years later, Napoleon's armies could move no faster than those of Julius Caesar — both depended upon horses and carts. But seventy years after Napoleon's death, steam trains could reach speeds of over 112 miles per hour. The industrial revolution was well under way and the economic era of agriculture, thousands of years old, was in less than a century replaced by the industrial age. A survival-of-the-fittest social system, feudalism that had lasted for hundred of years were quickly replaced by capitalism.

  More notably, and marking Thurow's fruitful use, he stresses important conjoints of punctuated equilibrium as the most relevant — and practical — themes for our current and dangerous situation. First, the common phenotype of punctuation leads him to recognize that general structural rules must underlie both the maintenance of stasis and, through their fracturing, the epi­sodes of punctuation as well. The rules will differ in social and natural sys­tems, but the general principle applies across domains. Thurow argues that stasis requires a meshing of technology and ideology, while their radical di­vergence initiates punctuation, a situation that we face today. (Marx, in an entirely different context, held a similar view about both the character of the rule and the punctuational outcome.)

  Technology and ideology are shaking the foundations of twenty-first-century capitalism. Technology is making skills and knowledge the only sources of sustainable strategic advantage. Abetted by the electronic me­dia, ideology is moving toward a radical form of short-run individual [Page 966] consumption maximization at precisely a time when economic success will depend upon the willingness and ability to make long-run social investments in skills, education, knowledge, and infrastructure. When technology and ideology start moving apart, the only question is when will the “big one” (the earthquake that rocks the system) occur. Para­doxically, at precisely the time when capitalism finds itself with no social competitors — its former competitors, socialism or communism, having died — it will have to undergo a profound metamorphosis (p. 326).

  Second, Thurow continually stresses the contingency implied by the scale change between causes of alteration in “normal” times (with greater poten­tial and range in social than in natural systems due to the Lamarckian char­acter of cultural inheritance) and the different modes and mechanisms of punctuational episodes. Thus, the rules we may establish from our experience of ordinary times cannot predict the nature or direction of any forthcoming punctuation.

  In a period of punctuated equilibrium no one knows that new social behavior patterns will allow humans to prosper and survive. But since old patterns don't seem to be working, experiments with different new ones have to be tried (p. 236) . . . How is capitalism to function when the important types of capital cannot be owned? Who is going to make the necessary long-run investments in skills, infrastructure, and research and de­velopment? How do the skilled teams that are necessary for success get formed? In periods of punctuated equilibrium there are questions with­out obvious answers that have to be answered (p. 309).

  Thurow therefore stresses the virtues of flexibility, ending his book (pp. 326-327) with an appropriate image for “the period of punctuated equi­librium” that “the tectonic forces altering the economic surface of the earth have created”:

  Columbus knew that the world was round, but he ... thought that the diameter of the world was only three quarters as big as it really is. He also overestimated the eastward land distance to Asia and therefore by subtraction grossly underestimated the westward water distance to Asia . . . Given the amount of water put on board, without the Americas Co­lumbus and all his men would have died of thirst and been unknown in our history books. Columbus goes down in history as the world's great­est explorer ... because he found the completely unexpected, the Ameri­cas, and they happened to be full of gold. One moral of the story is that it is important to be smart, but that it is even more important to be lucky. But ultimately Columbus did not succeed because he was lucky. He suc­ceeded because he made the effort to set sail in a direction never before taken despite a lot of resistance from those around him. Without that enormous effort he could not have been in the position to have a colossal piece of good luck. [Page 967]

  To end on a more personal note, if I were to cite any one factor as probably most important among the numerous influences that predisposed my own mind toward joining Niles Eldredge in the formulation of punctuated equilib­rium, I would mention my reading, as a first year graduate student in 1963, of one of the 20th century's most influential works at the interface of philoso­phy, sociology and the history of ideas: Thomas S. Kuhn's The Structure of Scientific Revolutions (1962). (My friend Mike Ross, then studying with the eminent sociologist of science R. K. Merton in the building next to Colum­bia's geology department, ran up to me one day in excitement, saying “you just have to read this book right away.” I usually ignore such breathless ad­monitions, but I respected Mike's judgment, and I'm surely glad that I fol­lowed his advice. In fact, I went right to the bookstore and bought a copy of Kuhn's slim volume.)

  Of course, Kuhn's notion of the history of change in scientific concepts advances a punctuational theory for the history of ideas — going from stable “paradigms” of “normal science” in the “puzzle solving” mode, through accumulating anomalies that build anxiety but do not yet force the basic struc­ture to change, through rapid transitions to new paradigms so different from the old that even “conserved” technical terms change their meaning to a suf­ficient extent that the two successive theories become “incommensurable.” The book has also served, I suspect, as the single most important scholarly impetus towards punctuational thinking in other disciplines.

  Since the appearance of our initial paper on punctuated equilibrium in 1972, several colleagues have pointed out to me that Kuhn himself, in a single passage, used the word “punctuated” to epitomize the style of change de­scribed by his theory. These colleagues have wondered if I borrowed the term, either consciously or unconsciously, from this foundational source. But I could not have done so. (I do not say this in an exculpatory way — for if I had so borrowed, I would be honored to say so, given my enormous respect and personal affection for Kuhn, and the pleasure I take in being part of his intel­lectual lineage. We did, but in an entirely different discussion about the defini­tion of paradigms, cite Kuhn's book in our 1972 paper.) Kuhn used the word “punctuated” in the 1969 “postscript” that he added to the second edition of his book (see quotation below). In 1972, I had only read the first edition.

  I mention this final point not as pure self-indulgence, but largely because Kuhn's single use of the word “punctuated,” located in the closing para­graphs of the seventh and last section (entitled “the nature of science”) of his postscript, expresses a surprising opinion that seems eminently exaptable as an appropriate finale to this chapter. Like all scholars whose works become widely known through constantly degraded repetition that strays further and further from unread original sources, Kuhn could become quite prickly about fallacious interpretations, and even more perturbed by bastardized and sim­plistic readings that caricatured h
is original richness.

  He therefore ended his postscript by discussing two “recurrent reactions” (1969, p. 207) to his original text. He regarded the first reaction (irrelevant to this chapter) as simply unwarranted, so he just tried to correct his critics. But [Page 968] the second reaction bothered him more — as “favorable” (p. 207) to his work but, in his view, “not quite right” in granting him too much credit. He states that, whereas he had certainly hoped to catch the attention of scientists, he cannot understand why scholars in nonscientific disciplines should have found his work enlightening. After all, he claims (p. 208), he had only tried to explain the classical punctuational views of the arts and humanities to practi­tioners of another field — science — where social and philosophical tradition had long clouded this evident point. (The word “punctuated” appears in this passage):

  To one last reaction to this book, my answer must be of a different sort. A number of those who have taken pleasure from it have done so less be­cause it illuminates science than because they read its main theses as ap­plicable to many other fields as well. I see what they mean and would not like to discourage their attempts to extend the position, but their reac­tion has nevertheless puzzled me. To the extent that the book portrays scientific development as a succession of tradition-bound periods punc­tuated by noncumulative breaks, its theses are undoubtedly of wide ap­plicability. But they should be, for they are borrowed from other fields. Historians of literature, of music, of the arts, of political development, and of many other human activities have long described their subjects in the same way. Periodization in terms of revolutionary breaks in style, taste, and institutional structure have been among their standard tools. If I have been original with respect to concepts like these, it has mainly been by applying them to the sciences, fields which had been widely thought to develop in a different way.

  To this passage, I can only respond that I see what be means, but I also think that Kuhn undercuts the range of his own originality and influence by misreading the very social context that inspired his work. Indeed, the ethos of science — the conviction that our history may be read as an ever closer ap­proach to an objective natural reality obtained by making better and better factual observations under the unvarying guidance of a timeless and rational procedure called “the scientific method” — does establish the most receptive context imaginable for mistaken notions about gradualistic and linear progressionism in the history of human thought. Indeed also, the traditions of disciplines that practice or study human artistic creativity — with their con­cepts of discrete styles and revolutionary breaks triggered by “genius” inno­vators — should have established punctuational models as preferable, if not canonical.

  But, as Kuhn acknowledges, his book enjoyed a substantial vogue among artists and humanists, who also felt surprised and enlightened by his punc­tuational theory for the history of ideas. I think that Kuhn underestimated the “back influence” of science upon preexisting fields in humanistic study. Eiseley (1958) labeled the formative era of evolutionary theory as “Darwin's century,” and we must never underestimate the influence of the Darwinian revolution, and of other 19th century notions, particularly the uniformitarian [Page 969] geology of Lyell, upon reconceptualizations of modes of discovery and forms of content in other disciplines, no matter how distant. Progressivistic gradual­ism — so central to most late 19th century versions of biological and geologi­cal history, and so strongly abetted by the appearance of “progress” (at least to Westerners) in the industrial and colonial expansion of Western nations, at least before the senseless destruction of the First World War shattered all such illusions forever — became a paradigm for all disciplines, not just for the sci­ences. Kuhn may have called upon some classical notions from the arts and humanities to construct a great reform for science; but his corrective also, and legitimately, worked back upon a source that had strayed from a crucial root idea to become beguiled by a contrary notion about change that seemed more “modern” and “prestigious.”*

  In addition, and finally, I think that Kuhn underestimated the potential role of scientific ideas in resolving old puzzles that have long stymied humanistic understanding of artistic creativity, and that remain seriously burdened by the hold of theories as ancient as the Platonic notion of essences and universals. In a lovely passage, directly following the “punctuational” quotation just cited, Kuhn acknowledges that the Darwinian concept of species as varying [Page 970] populations without essences (and even without abstractions, like mean val­ues, to act as preferred or defining states) might break through a powerful and constraining prejudice, ultimately rooted in Platonic essentialism, that leads us to search for chimaerical idealizations as ultimate standards of com­parison in the definition and evaluation of artistic “style.” Kuhn writes, now viewing styles as paradigms and paradigms as higher level individuals like bi­ological species (pp. 208-209): “Conceivably the notion of a paradigm as a concrete achievement, an exemplar, is a second contribution [of my book]. I suspect, for example, that some of the notorious difficulties surrounding the notion of style in the arts may vanish if paintings can be seen to be modeled on one another rather than produced in conformity to some abstracted can­ons of style.”

  Punctuated equilibrium represents just one localized contribution, from one level of one discipline, to a much broader punctuational paradigm about the nature of change — a worldview that may, among scholars of the new mil­lennium, be judged as a distinctive and important movement within the intel­lectual history of the later 20th century. I am pleased that our particular formulation did gain a hearing and did, for that reason, encourage other scholars over a wide range of scientific and nonscientific disciplines (as illus­trated in this chapter) to consider the larger implications of the more general punctuational model for change. I am especially gratified that many of these scholars did not just borrow punctuated equilibrium as a vague metaphor, however useful, but also understood, and found fruitful, some of the more specific “conjoints” distinctive to the level and phenomenon of punctuated equilibrium, but also applicable elsewhere. For the punctuational paradigm encompasses much more than a loose and purely descriptive claim about phenotypes of pulsed change, but also embodies a set of convictions about how the structures and processes of nature must be organized across all scales and causes to yield this commonality of observed results. Only in this sense — punctuated equilibrium as a distinctive contribution to a much larger and ongoing effort — can I understand Ruse's gracious reappraisal of his initial negativity toward punctuated equilibrium: “Grant then that there is indeed something going on that looks like a paradigm (or paradigm difference) in ac­tion. People (like my former self) who dismissed the idea were wrong — and missing something rather interesting to boot” (Ruse, 1992, p. 162).

  From the more restricted perspective of the aims of this particular book, I can at least assert that punctuated equilibrium unites the three definitive themes of this volume — the three legs of my tripod of support for an expan­sion of Darwinian theory, thereby leading me to conclude that an empirically legitimate and logically sound structure does encompass and unite these three arguments into a coherent and general reformulation and extension of the Darwinian paradigm: the hierarchical theory of selection on leg one, the structuralist critique of Darwinian functionalism and adaptationism on leg two, and the paleontologist's conviction (leg three) that general macroevolutionary processes and mechanisms cannot be fully elucidated by uniformitarian [Page 971] extrapolation from the smallest scale of our experiments and personal observations. Punctuated equilibrium has proven its mettle in:

  1. Elucidating and epitomizing what may be the primary process of a distinctive level in the evolutionary hierarchy: the role of species as Darwin­ian individuals, and the speciational reformulation of macroevolution — for leg one.

  2. Defining (and, in part, thereby creating) the issue of stasis as a subject for study, and in helping to explicate the structural ru
les that hold entities in ac­tive stasis at various levels, but then permit rapid transition to qualitatively different states — for leg two.

  3. Stressing that level-bound punctuational breaks preclude the prediction or full understanding of extensive temporal change from principles of anagenetic transformation at the lowest level (a mode of evolution, moreover, that punctuated equilibrium regards as rare in any case), thus emphasizing contingency and denying extrapolationist premises and methodologies — for leg three.

  In developing this set of implications, I do hold, in my obviously biased way, that punctuated equilibrium has performed some worthy intellectual service. The relative frequency of its truth-value, of course, must be regarded as another matter entirely, and an issue that only time can fully resolve. But I would maintain that, in the quarter century following its original formula­tion, punctuated equilibrium has at least prevailed, against an initial skepti­cism of active and general force and frequency, in three central empirical claims (quite independent of any theoretical weight that evolutionary biology may ultimately wish to assign): (1) documentation of the basic mechanism in cases now too numerous and too minutely affirmed to deny status as an im­portant phenomenon in macroevolutionary pattern; (2) validation of stasis as a genuine, pervasive, and active phenomenon in the geological history of most species; and (3) establishment of predominant relative frequency in enough comprehensive and well-bounded domains to assure the control of punctuated equilibrium over substantial aspects of the phyletic geometry of macroevolution. A fourth, and ultimately more important, issue for evolu­tionary theory remains unresolved: the implications of these empirical find­ings for the role of genuine selection among species-individuals (rather than merely descriptive species-sorting as an upwardly cascading expression of conventional Darwinian selection acting at the organismic level) as the causal foundation of macroevolutionary pattern.

 

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