Review: The Paleobiological Revolution
Work under Review
For many years we have needed a collection of essays and historical reminiscences on just how the paleobiological revolution, or in another sense the emergence of macroevolution as a field, got started in the 1960s and 1970s. Looking back on the scientific literature of the time, and contrasting it to what came before, is much like looking at the cultural impact on a civilization when it is invaded (by Romans, Americans, or Visigoths — complete your own preferred metaphor). The world of paleontology changed completely because in addition to all the traditional kinds of study in taxonomy, stratigraphy, and so on, here was all this new theory that harnessed an incredible store of information and started asking questions about the major features of life and its environments through time. The chapters in this book remind us not only how far the field has come, but also how incredibly central it is to the study of any kind of evolution, even if most population biologists are oblivious to it. The world of evolutionary biology changed utterly as well, although most evolutionary biologists still do not realize it. This book is a masterpiece, brilliantly conceived and written, and it is essential to the conceptual training of every evolutionary biologist.
The editors are David Sepkoski and Michael Ruse, neither one a biologist or paleontologist. However, David, the son of Jack Sepkoski, clearly absorbed the developing Zeitgeist of the field as he grew up, and the collection of contributing authors is amazing. Not only that: the editors have generally gotten terrific (and usually concordant) historical accounts from the participants. But this is not a collection of “how I won the war”stories.The major participants who launched this field (some not realizing that they were doing so, others very consciously so) were responding to a broad common perception that the basic data of paleontology for too long had been considered incapable of contributing anything to evolutionary theory, and so remained the mere “handmaiden” to geology (in a frequently used phrase) that could only help the real scientists tell them what age their rocks were and who lived in them.
A “turning point” in the recent history of macroevolution as a field, and one on which several authors focus, is the brief essay in Nature in 1984 by the biologist John Maynard Smith. Maynard Smith had been at the now-legendary Macroevolution conference in Chicago in 1980, organized by Joel Cracraft and others, and although he never really understood very well all the things that were going on, he had begun to see the importance of the emergence of this young field. Famously, Maynard Smith remarked at the end of his paper, “Palaeontology has been too long absent from the high table. Welcome back.” That was seen as vindication by many, as snobbism by others, but the interesting thing was that the paleobiologists had been setting their own table for years, and the fare was rather more interesting than what was at the “high table” of population theory and quantitative genetics.
Maynard Smith found punctuated equilibria, the enfant terrible of macroevolutionary theory, among the most promising new developments, although he changed his mind some years later (again, not really understanding the evidence or how to evaluate it) and wound up repeatedly vilifying Stephen Jay Gould in print, for reasons that must have been deeper than mere science. But macroevolution was far more than a reassessment of the tempo of morphological change through time, or even the mode of speciation as seen in the fossil record. It also featured the concerted efforts to understand the actual record of diversity through time and to separate it from various biases; the emergence of the study of extinction — background and mass; the development of the field of paleoecology as a quantitative, experimental, historical science; and the study of the relationship between paleontology’s pattern data of evolution in the long run and population biology’s process data of generational variability and change.
Sociologically and scientifically, it’s interesting to see what has been included in this book and what has been left out. The strong emphasis on paleobiology at the University of Chicago is no accident: that school encompassed the quantitative revolution in the field, and its eponymous journal was begun there. Many of its major thinkers, including Ralph Johnson, Tom Schopf, later Dave Raup and Jack Sepkoski, and later Dave Jablonski, Sue Kidwell, and many others, made Chicago the Action Central of macroevolution (where else to hold the 1980 conference?).
Many contributors to this book detail the geographic currents of cross-fertilization through migrations of students and professors, productive meetings and conferences, and reviews of manuscripts. The emphasis, as a result, is almost entirely on invertebrate paleontology. And this actually explains the omissions. Oddly enough, there is almost no mention of phylogenetic systematics (cladistics), which revolutionized all of biology beginning in the 1970s. However, invertebrate paleontologists were slow to catch on, probably because they thought they could track evolution stratigraphically and did not need independent phylogenetic analysis of characters, and also because most of their critters’ skeletons had far fewer characters to code than those of vertebrates. It took many years before invertebrate specialists moved beyond taxonomy to phylogeny, or used phylogenetic analysis to improve the understanding of missing diversity in their records.
There is in fact very little about fossil vertebrates, plants, or microorganisms in this book, even though specialists in each field contributed heavily to macroevolutionary questions. It is also puzzling why no assessment of Leigh Van Valen’s work is included, inasmuch as his “Red Queen hypothesis”is truly one of the seminal papers of the last century, having influenced macroecology, game theory, sexual selection, extinction theory, and optimality theory. Nor was this his only influential paper. Van Valen, a long-time maverick in Chicago, is often perceived as a radical but is perhaps the most ultra-Darwinian of all evolutionary thinkers. Many have used his work without fully comprehending his compass, which is overdue for assessment.
But these omissions can be explained by a simple fact: the invertebrate folks have most of the best fossils. This gives us the most complete record of layer-by-layer change through time, often with exquisite preservation and copious samples amenable to statistical study as significant as can be done on living organisms (and with much more extensive temporal range). Vertebrate fossils are generally fewer, more poorly constrained stratigraphically, and liable to be scattered or distorted; fossil plants are generally preserved as isolated organs, not whole parts, and so their study has mostly focused on anatomy, morphology, and physiology of individual forms and sometimes communities. But both these fields have been able to do what most studies of invertebrates have not (or not as fully): document the origin and evolution of major adaptations of the major groups through time — another dimension largely omitted from the “official” paleobiological revolution, at least as recorded in these pages.
Stephen Jay Gould is so well known that he can serve as a pretty average example of why the material enables the questions. Gould saw the advantage of the methodological clarity of phylogenetics, but never used it much; he focused on morphological change in stratigraphic context, on morphological theory, and on extinction. He gave little thought to how major groups and major adaptations evolve (apart from the Cambrian Explosion, a subject for several authors here). He did not see how functional morphology could contribute much in the way of new theoretical insights for evolution, which is fair enough, but he also did not see how we could harness the study of functional evolution to phylogenetic trees to test hypotheses about major innovations. He was more interested in extinctions than originations, like most invertebrate paleontologists, and why not? After all, the geologic periods were originally recognized on the basis of invertebrate extinction events. This is not to criticize, but to provide some perspective on why certain questions are (can be) studied based on certain material, and others not. It is equally true that if we are interested in looking at the origin of major adaptive change, we would not choose fruit flies.
There are so many wonderful papers in this book that it is hard to choose favorites, but for me different papers are favorites for different reasons. I will just name several in order of appearance. Patricia Princehouse provides one of the most nuanced and perceptive articles on the evolution and reception of punctuated equilibria ever written, replete with personal interviews that will sometimes surprise. I found myself saying continually, “yes, yes, that’s exactly what happened,” and more of this kind of insight is needed in the history of evolution. Manfred Laublicher and Karl Niklas provide an absolutely exquisite essay on the morphological tradition in German paleontology mostly during the Modern Synthesis, which helps to explain why so much of Europe and so many of the fields allied to it were left out, and why it was so difficult to get back in the game.
I really liked both of David Sepkoski’s essays on the development of paleobiology and especially punctuated equilibria, although I would take issue with him on some interpretations of how “radical” these ideas were meant to be. He is coming out soon with his own book on the history of the field, which is greatly anticipated. Arnold Miller’s contextual and detailed chronicle of the “Consensus Paper” on the shape of invertebrate diversity through time is a real masterpiece, putting everything into perspective and relying on his own experience with the players in question as well as their accounts. Dick Bambach’s essay on his own personal journey from traditional paleoecologist to macroevolutionary theorist is one among many (and perhaps primus inter pares) frank, stimulating, perceptive, self-aware accounts that should inspire any graduate student in any field to learn how truly great scientists develop (other essays by Richard Fortey, Bill Schopf, Jim Valentine, and Tony Hallam also qualify). Rebecca German offers a trenchant and very useful first-hand commentary on the development of the field from her perspective as a student and colleague of many of the major players. And the envoi by David Jablonski on where paleobiology should go from here is about the best possible thing for a working paleontologist, as well as a beginning student, to read in order to learn from a true master where things stand and where the future can be.
The sole clinker in the book is Joe Cain’s screed on Gould’s alleged “ritual patricide” of George Gaylord Simpson, an act that Cain maintains was necessary in order for Gould’s punctuated equilibrium to succeed and replace Simpson’s pioneering work. Cain is allowed vituperative attacks without substantiation, including a table of Gould’s alleged misdeeds with no references or citations at all. He completely misrepresents Gould’s great respect for Simpson (Gould once called Tempo and Mode in Evolution “the closest thing to a one-man show” in the field), ignores Gould’s knowing historiographic contextualization of Simpson’s contributions (including the pressure Simpson faced to water down Tempo and Mode’s emphasis on quantum evolution, rewritten in Major Features of Evolution), and overlooks the universally accepted fact that the extrapolationist role to which Simpson’s paleontology was confined by the Modern Synthesis gurus stalled out any possible theoretical contributions that paleontology could make to evolutionary theory. I did not know Simpson but I knew Gould well, and we discussed his respect for Simpson’s contributions. This essay is character assassination, not scholarship, and the editors should be embarrassed for including it.
Apart from this, the essays in The Paleobiological Revolution should become standard reading for all evolutionary biologists, especially those in the field of paleontology, and the authors and editors should be justifiably proud of the first major treatment of the genesis and history of what has brought the whole field of evolution to a higher table.
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