Wonderful Life: The Burgess Shale and the Nature of History

  But historical science is not worse, more restricted, or less capable of achieving firm conclusions because experiment, prediction, and subsumption under invariant laws of nature do not represent its usual working methods. The sciences of history use a different mode of explanation, rooted in the comparative and observational richness of our data. We cannot see a past event directly, but science is usually based on inference, not unvarnished observation (you don’t see electrons, gravity, or black holes either).

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  A PLEA FOR THE HIGH STATUS OF NATURAL HISTORY

  In no other way but this false ordering by status among the sciences can I understand the curious phenomenon that led me to write this book in the first place—namely, that the Burgess revision has been so little noticed by the public in general and also by scientists in other disciplines. Yes, I understand that science writers don’t consult the Philosophical Transactions of the Royal Society, London, and that hundred-page anatomical monographs can seem rather daunting to those unschooled in the jargon. But we cannot charge Whittington and colleagues with hiding the good news. They have also published in the general journals that science writers do read—principally Science and Nature. They have written half a dozen prominent “review articles” for scientific colleagues. They have also composed a good deal for general audiences, including articles for Scientific American and Natural History, and a popular guide for Parks Canada. They know the implications of their work, and they have tried to get the message across; others have also aided (I have written four essays on the Burgess Shale for Natural History). Why has the story not taken hold, or been regarded as momentous?

  An interesting contrast, hinting at a solution, might be drawn between the Burgess revision and the Alvarez theory linking the Cretaceous extinction to extraterrestrial impact. I regard these two as the most important paleontological discoveries of the past twenty years. I think that they are equal in significance and that they tell the same basic story (as illustrations of the extreme chanciness and contingency of life’s history: decimate the Burgess differently and we never evolve; send those comets into harmless orbits and dinosaurs still rule the earth, precluding the rise of large mammals, including humans). I hold that both are now well documented, the Burgess revision probably better than the Alvarez claim. Yet the asymmetry of public attention has been astonishing. Alvarez’s impact theory has graced the cover of Time, been featured in several television documentaries, and been a subject of comment and controversy wherever science achieves serious discussion. Few nonprofessionals have ever heard of the Burgess Shale—making this book necessary.

  I do understand that part of this difference in attention simply reflects our parochial fascination with the big and the fierce. Dinosaurs are destined for more attention than two-inch “worms.” But I believe that the major ingredient—particularly in the decision of science writers to avoid the Burgess Shale—lies with the stereotype of the scientific method, and the false ordering of sciences by status. Luis Alvarez, who died as I was writing this book, was a Nobel laureate and one of the most brilliant physicists of our century; he was, in short, a prince of science at the highest conventional grade. The evidence for his theory lies in the usual stuff of the laboratory—precise measurements made with expensive machinery on minute quantities of iridium. The impact theory has everything for public acclaim—white coats, numbers, Nobel renown, and location at the top of the ladder of status. The Burgess redescriptions, on the other hand, struck many observers as one funny thing after another—just descriptions of some previously unappreciated, odd animals from early in life’s history.

  I loved Luie Alvarez for the excitement that he injected into my field. Our personal relationship was warm, for I was one of the few paleontologists who liked what he had to say from the outset (though not always, in retrospect, for good reasons). Yet, de mortuis nil nisi bonum notwithstanding, I must report that Luie could also be part of the problem. I do appreciate his frustration with so many paleontologists who, caught by traditions of gradualism and terrestrial causation, never paid proper attention to his evidence. Yet Luie often lashed out at the entire profession, and at historical science in general, claiming, for example, in an already infamous interview with the New York Times, “I don’t like to say bad things about paleontologists, but they’re really not very good scientists. They’re more like stamp collectors.”

  I give Luie credit for saying out loud what many scientists of the stereotype think but dare not say, in the interests of harmony. The common epithet linking historical explanation with stamp collecting represents the classic arrogance of a field that does not understand the historian’s attention to comparison among detailed particulars, all different. This taxonomic activity is not equivalent to licking hinges and placing bits of colored paper in preassigned places in a book. The historical scientist focuses on detailed particulars—one funny thing after another—because their coordination and comparison permits us, by consilience of induction, to explain the past with as much confidence (if the evidence is good) as Luie Alvarez could ever muster for his asteroid by chemical measurement.

  We shall never be able to appreciate the full range and meaning of science until we shatter the stereotype of ordering by status and understand the different forms of historical explanation as activities equal in merit to anything done by physics or chemistry. When we achieve this new taxonomic arrangement of plurality among the sciences, then, and only then, will the importance of the Burgess Shale leap out. We shall then finally understand that the answer to such questions as “Why can humans reason?” lies as much (and as deeply) in the quirky pathways of contingent history as in the physiology of neurons.

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  The firm requirement for all science—whether stereotypical or historical—lies in secure testability, not direct observation. We must be able to determine whether our hypotheses are definitely wrong or probably correct (we leave assertions of certainty to preachers and politicians). History’s richness drives us to different methods of testing, but testability is our criterion as well. We work with our strength of rich and diverse data recording the consequences of past events; we do not bewail our inability to see the past directly. We search for repeated pattern, shown by evidence so abundant and so diverse that no other coordinating interpretation could stand, even though any item, taken separately, would not provide conclusive proof.

  The great nineteenth-century philosopher of science William Whewell devised the word consilience, meaning “jumping together,” to designate the confidence gained when many independent sources “conspire” to indicate a particular historical pattern. He called the strategy of coordinating disparate results from multifarious sources consilience of induction.

  I regard Charles Darwin as the greatest of all historical scientists. Not only did he develop convincing evidence for evolution as the coordinating principle of life’s history, but he also chose as a conscious and central theme for all his writings—the treatises on worms, coral reefs, and orchids, as well as the great volumes on evolution—the development of a different but equally rigorous methodology for historical science (Gould, 1986). Darwin explored a variety of modes for historical explanation, each appropriate for differing densities of preserved information (Gould, 1986, pp. 60–64), but his central argument rested on Whewell’s consilience. We know that evolution must underlie the order of life because no other explanation can coordinate the disparate data of embryology, biogeography, the fossil record, vestigial organs, taxonomic relationships, and so on. Darwin explicitly rejected the naive but widely held notion that a cause must be seen directly in order to qualify as a scientific explanation. He wrote about the proper testing of natural selection, invoking the idea of consilience for historical explanation:

  Now this hypothesis may be tested—and this seems to me the only fair and legitimate manner of considering the whole question—by trying whether it explains several large and independent classes of facts; such as the geological succession o
f organic beings, their distribution in past and present times, and their mutual affinities and homologies. If the principle of natural selection does explain these and other large bodies of facts, it ought to be received (1868, vol. 1, p. 657).

  But historical scientists must then proceed beyond the simple demonstration that their explanations can be tested by equally rigorous procedures different from the stereotype of the “scientific method”; they must also convince other scientists that explanations of this historical type are both interesting and vitally informative. When we have established “just history” as the only complete and acceptable explanation for phenomena that everyone judges important—the evolution of the human intelligence, or of any self-conscious life on earth, for example—then we shall have won.

  Historical explanations take the form of narrative: E, the phenomenon to be explained, arose because D came before, preceded by C, B, and A. If any of these earlier stages had not occurred, or had transpired in a different way, then E would not exist (or would be present in a substantially altered form, E’, requiring a different explanation). Thus, E makes sense and can be explained rigorously as the outcome of A through D. But no law of nature enjoined E; any variant E’ arising from an altered set of antecedents, would have been equally explicable, though massively different in form and effect.

  I am not speaking of randomness (for E had to arise, as a consequence of A through D), but of the central principle of all history—contingency. A historical explanation does not rest on direct deductions from laws of nature, but on an unpredictable sequence of antecedent states, where any major change in any step of the sequence would have altered the final result. This final result is therefore dependent, or contingent, upon everything that came before—the unerasable and determining signature of history.

  Many scientists and interested laypeople, caught by the stereotype of the “scientific method,” find such contingent explanations less interesting or less “scientific,” even when their appropriateness and essential correctness must be acknowledged. The South lost the Civil War with a kind of relentless inevitability once hundreds of particular events happened as they did—Pickett’s charge failed, Lincoln won the election of 1864, etc., etc., etc. But wind the tape of American history back to the Louisiana Purchase, the Dred Scott decision, or even only to Fort Sumter, let it run again with just a few small and judicious changes (plus their cascade of consequences), and a different outcome, including the opposite resolution, might have occurred with equal relentlessness past a certain point. (I used to believe that Northern superiority in population and industry had virtually guaranteed the result from the start. But I have been persuaded by recent scholarship that wars for recognition rather than conquest can be won by purposeful minorities. The South was not trying to overrun the North, but merely to secure its own declared borders and win acknowledgment as an independent state. Majorities, even in the midst of occupation, can be rendered sufficiently war-weary and prone to withdraw by insurgencies, particularly in guerilla form, that will not relent.)

  Suppose, then, that we have a set of historical explanations, as well documented as anything in conventional science. These results do not arise as deducible consequences from any law of nature; they are not even predictable from any general or abstract property of the larger system (as superiority in population or industry). How can we deny such explanations a role every bit as interesting and important as a more conventional scientific conclusion? I hold that we must grant equal status for three basic reasons.

  1. A question of reliability. The documentation of evidence, and probability of truth by disproof of alternatives, may be every bit as conclusive as for any explanation in traditional science.

  2. A matter of importance. The equal impact of historically contingent explanations can scarcely be denied. The Civil War is the focus and turning point of American history. Such central matters as race, regionalism, and economic power owe their present shape to this great event that need not have occurred. If the current taxonomic order and relative diversity of life are more a consequence of “just history” than a potential deduction from general principles of evolution, then contingency sets the basic pattern of nature.

  3. A psychological point. I have been too apologetic so far. I have even slipped into the rhetoric of inferiority—by starting from the premise that historical explanations may be less interesting and then pugnaciously fighting for equality. No such apologies need be made. Historical explanations are endlessly fascinating in themselves, in many ways more intriguing to the human psyche than the inexorable consequences of nature’s laws. We are especially moved by events that did not have to be, but that occurred for identifiable reasons subject to endless mulling and stewing. By contrast, both ends of the usual dichotomy—the inevitable and the truly random—usually make less impact on our emotions because they cannot be controlled by history’s agents and objects, and are therefore either channeled or buffeted, without much hope for pushing back. But, with contingency, we are drawn in; we become involved; we share the pain of triumph or tragedy. When we realize that the actual outcome did not have to be, that any alteration in any step along the way would have unleashed a cascade down a different channel, we grasp the causal power of individual events. We can argue, lament, or exult over each detail—because each holds the power of transformation. Contingency is the affirmation of control by immediate events over destiny, the kingdom lost for want of a horseshoe nail. The Civil War is an especially poignant tragedy because a replay of the tape might have saved a half million lives for a thousand different reasons—and we would not find a statue of a soldier, with names of the dead engraved on the pedestal below, on every village green and before every county courthouse in old America. Our own evolution is a joy and a wonder because such a curious chain of events would probably never happen again, but having occurred, makes eminent sense. Contingency is a license to participate in history, and our psyche responds.

  The theme of contingency, so poorly understood and explored by science, has long been a mainstay of literature. We note here a situation that might help to breach the false boundaries between art and nature, and even allow literature to enlighten science. Contingency is Tolstoy’s cardinal theme in all his great novels. Contingency is the source of tension and intrigue in many fine works of suspense, most notably in a recent masterpiece by Ruth Rendell (writing as Barbara Vine), A Fatal Inversion (1987)—a chilling book describing a tragedy that engulfs the lives and futures of a small community through an escalating series of tiny events, each peculiar and improbable (but perfectly plausible) in itself, and each entraining a suite of even stranger consequences. A Fatal Inversion is so artfully and intricately plotted by this device that I must view Rendell’s finest work as a conscious text on the nature of history.

  Two popular novels of the past five years have selected Darwinian theory as their major theme. I am especially intrigued and pleased that both accept and explore contingency as the theory’s major consequence for our lives. In this correct decision, Stephen King and Kurt Vonnegut surpass many scientists in their understanding of evolution’s deeper meanings.

  King’s The Tommyknockers (1987) fractures a tradition in science fiction by treating extraterrestrial “higher intelligences” not as superior in general, wiser, or more powerful, but merely as quirky hangers-on in the great Darwinian game of adaptation by differential reproductive success in certain environments. (King refers to this persistence as “dumb evolution”; I just call it Darwinism.)* Such equivocal success by endless and immediate adjustment breeds contingency, which then becomes the controlling theme of The Tommyknockers—as the aliens fail in their plans for earth, thanks largely to evasive action by one usually ineffective, cynical, and dipsomaniacal English professor. King muses on the nature of controlling events in contingent sequences, and on their level of perceived importance at various scales:

  I would not be the one to tell you there are no planets anywhere in the universe that are not l
arge dead cinders floating in space because a war over who was or was not hogging too many dryers in the local Laundromat escalated into Doomsville. No one ever really knows where things will end—or if they will.… Of course we may blow up our world someday with no outside help at all, for reasons which look every bit as trivial from a standpoint of light-years; from where we rotate far out on one spoke of the Milky Way in the Lesser Magellanic Cloud, whether or not the Russians invade the Iranian oilfields or whether NATO decides to install American-made Cruise missiles in West Germany may seem every bit as important as whose turn it is to pick up the tab for five coffees and a like number of Danish.

  Kurt Vonnegut’s Galápagos (1985) is an even more conscious and direct commentary on the meaning of evolution from a writer’s standpoint. I feel especially gratified that a cruise to the Galápagos, a major source of Vonnegut’s decision to write the book, should have suggested contingency as the cardinal theme taught by Darwin’s geographic shrine. In Vonnegut’s novel, the pathways of history may be broadly constrained by such general principles as natural selection, but contingency has so much maneuvering room within these boundaries that any particular outcome owes more to a quirky series of antecedent events than to channels set by nature’s laws. Galápagos, in fact, is a novel about the nature of history in Darwin’s world. I would (and do) assign it to students in science courses as a guide to understanding the meaning of contingency.