Wilkins_FM.qxd 6/4/09 8:59 AM Page i SPECIES Wilkins_FM.qxd 6/4/09 8:59 AM Page ii SPECIES AND SYSTEMATICS The Species and Systematics series will investigate fundamental and practical aspects of systematics and taxonomy in a series of comprehensive volumes aimed at students and researchers in systematic biology and in the history and philosophy of biology. The book series will examine the role of descriptive taxonomy, its fusion with cyber-infrastructure, its future within biodiversity studies, and its importance as an empirical science. The philosophical consequences of classification, as well as its history, will be among the themes explored by this series, including systematic methods, empirical studies of taxonomic groups, the history of homology, and its significance in molecular systematics. Editor-in-Chief: Malte C. Ebach (International Institute for Species Exploration, Arizona State University, USA) Editorial Board Marcelo R. de Carvalho (Universidade de São Paulo, Brazil) Anthony C. Gill (Arizona State University, USA) Andrew L. Hamilton (Arizona State University, USA) Brent D. Mishler (University of California, Berkeley, USA) Juan J. Morrone (Universidad Nacional Autónoma de México, Mexico) Lynne R. Parenti (Smithsonian Institution, USA) Quentin D. Wheeler (Arizona State University, USA) John S. Wilkins (University of Sydney, Australia) Kipling Will (University of California, Berkeley, USA) David M. Williams (Natural History Museum, London, UK) University of California Press Editor: Charles R. Crumly Wilkins_FM.qxd 6/4/09 8:59 AM Page iii SPECIES A HISTORY OF THE IDEA John S. Wilkins UNIVERSITY OF CALIFORNIA PRESS BERKELEY LOS ANGELES LONDON Wilkins_FM.qxd 6/8/09 11:36 AM Page iv University of California Press, one of the most distinguished university presses in the United States, enriches lives around the world by advancing scholarship in the humanities, social sciences, and natural sciences. Its activities are supported by the UC Press Foundation and by philanthropic contributions from individuals and institutions. For more informa- tion, visit www.ucpress.edu. Species and Systematics, Vol. 1 University of California Press Berkeley and Los Angeles, California University of California Press, Ltd. London, England © 2009 by the Regents of the University of California Library of Congress Cataloging-in-Publication Data Wilkins, John S., 1955– Species : a history of the idea / John S. Wilkins. p. cm. — (Species and systematics ; v. 1) Includes bibliographical references and index. ISBN 978-0-520-26085-6 (cloth : alk. paper) 1. Species—History. 2. Species—Philosophy. I. Title. QH83.W527 2009 578.01'2—dc22 2009009184 Manufactured in the United States of America 16 15 14 13 12 11 10 09 10987654321 The paper used in this publication meets the minimum requirements of ANSI/NISO Z39.48-1992 (R 1997) (Permanence of Paper). Cover image: Ascidiae (sea squirts and tunicates). From Tafel 85 of Ernst Haeckel, Art Forms in Nature: The Prints of Ernst Haeckel. Courtesy of Prestel: Munich, Berlin, London, New York, 1998, 2009. Wilkins_FM.qxd 6/4/09 8:59 AM Page v Contents Preface vii Acknowledgments xiii Prologue 1 The Classical Era: Science by Division 9 The Medieval Bridge 35 Species and the Birth of Modern Science 47 The Early Nineteenth Century: A Period of Change 97 Darwin and the Darwinians 129 The Species Problem Arises 165 The Synthesis and Species 181 Modern Debates 197 Reproductive Isolation Concepts 197 Evolutionary Species Concepts 201 Phylogenetic Species Concepts 205 Other Species Concepts 216 Historical Summary and Conclusions 227 Notes 235 References 251 Index 289 About the Author 305 Wilkins_FM.qxd 6/4/09 8:59 AM Page vi This Page Left Intentionally Blank Wilkins_FM.qxd 6/4/09 8:59 AM Page vii Preface The history of research into the philosophy of language is full of men (who are rational and mortal animals), bache- lors (who are unmarried adult males), and tigers (though it is not clear whether we should define them as feline animals or big cats with a yellow coat and black stripes). Umberto Eco [1999: 9] “What sort of insects do you rejoice in, where you come from?” the Gnat inquired. “I don’t rejoice in insects at all,” Alice explained, “because I’m rather afraid of them — at least the large kinds. But I can tell you the names of some of them.” “Of course they answer to their names?” the Gnat remarked carelessly. “I never knew them do it.” “What’s the use of their having names,” the Gnat said, “if they won’t answer to them?” “No use to them,” said Alice; “but it’s useful to the people that name them, I suppose. If not, why do things have names at all?” “I can’t say,” the Gnat replied. “Further on, in the wood down there, they’ve got no names.” Lewis Carroll [1962: 225] Why look at one concept in science, out of context of the larger the- ories, practices, and societies in which it occurs? Why trace “species”? This sort of question is raised by both philosophers and historians when histories of scientific ideas are written. Philosophers tend to dislike history for several reasons. One is that they often address issues and ideas as if the opponent is sitting across the symposium table from them, no matter whether that opponent lived last week, last century, or last millennium. Philosophers of science often treat history as a source of anecdotes to illustrate some more general point, such as the way the Copernican revolution changed philosophical un- derstanding or how genes overcame vitalism. Famously or infamously, vii Wilkins_FM.qxd 6/4/09 8:59 AM Page viii viii / PREFACE Imre Lakatos “rationally reconstructed” the history of scientific ideas in a footnote, because history is messy and failed to clearly illustrate the philosophical point. Historians tend to dislike intellectual histories, because such histories treat ideas as free-floating objects (“free-floating rationales,” as Dennett calls them) independent of the individual psychologies and life histories, and of the social conditions in which they were raised and elaborated. Also, histories of ideas are too easy to do. All you need do is find some apparent resemblance between ideas at time a and time b, and you have a narrative. Historians, rightly, want to see actual historical influences and the effects of social and cultural contexts, the differing epistemes at work. Both professions can go too far. I think history comes in a number of scales, which following a practice in ecology, I will call alpha history, beta history, and gamma history. Alpha history is done by investigating archives and looking at locales and artifacts. It is hard and local work, and will give the data of the larger-scale histories. Beta history is done by covering a restricted period, or biography, or event. It relies on the alpha material and synthesizes it into a narrative explanation of the sub- ject. Gamma history, though, is out of fashion. Rather than being a “life and times” or “history of the period,” it attempts to take alpha and beta historical work and synthesize a grand-scale narrative. And because a really grand-scale narrative is almost impossible to do by one person, it pays to limit the subject to something manageable. This book is at the edge (some might uncharitably say, over the edge) of that limit. But if gamma history is not worth doing, why is alpha and beta history? Philosophy of science has become increasingly grounded in history. It is becoming the norm for philosophers of science to appeal closely to the historical development, failures as well as successes, or a given discipline or problem. Majorie Grene and Ian Hacking are perhaps the exemplars of this approach, although David Hull has also made a plea for actual examples in philosophy of biology [Hull 1989a]. And historians of sci- ence such as Polly Winsor and Jan Sapp have offered excellent case stud- ies and narratives of all three kinds for philosophers to use. There is a shift toward this now, and that might justify a conceptual history at this time. However, there’s another reason for writing this now, and that is that if philosophers don’t do this, and historians don’t, the scientists will, and have. A major target of this book is the scientist-developed essen- tialism story of the past fifty years. Polly Winsor and Ron Amundson, among others, have written critiques of the view that before Darwin, Wilkins_FM.qxd 6/4/09 8:59 AM Page ix PREFACE / ix every biologist was held in thrall to Aristotle’s essentialist biology, but there is no overall summary of this. Also, the essentialism story is used to justify or critique various species conceptions by the biologists them- selves. History has a role in scientific debate. Generally, scientists have a “rolling wall of fog” that trails behind them at various distances for different disciplines, above which only the peaks of mountains of the Greats can be seen. In medical biology, for instance, this wall is about five years behind the present. Little is cited before that, and those works that are, are cited by nearly everyone. So there is a ten- dency for what Kuhn called “textbook history” to become the common property of all members of the discipline. However, taxonomy is an un- usual discipline, in that the classical works are more widely cited and appealed to than in most other sciences. The ideas of an eighteenth- century Swede or French author can carry weight in a way that the genetics or physics of that time do not. Partly this is because a large element of taxonomy is conceptual: logical and metaphysical ideas, which change slowly, carry probative force. So asking “What is a species?” is to ask a historical as well as a present question, and how the notion of species arrived at the present debate in part defines that debate.