PHILOSOPHY OF BIOLOGY SECOND EDITION -i- [This page intentionally left blank.] -ii- Also by Elliott Sober Simplicity The Nature of Selection: Evolutionary Theory in Philosophical Focus Reconstructing the Past: Parsimony, Evolution, and Inference Core Questions in Philosophy Reconstructing Marxism: Explanation and the Theory of History (with Erik Wright and Andrew Levine) From a Biological Point of View: Essays in Evolutionary Philosophy Unto Others: The Evolution and Psychology of Unselfish Behavior (with David Sloan Wilson) -iii- Dimensions of Philosophy Series Norman Danielsand Keith Lehrer, Editors Philosophy of Biology, Second Edition, Elliott Sober Contemporary Continental Philosophy, Robert D'Amico Philosophical Ethics, Stephen Darwall Normative Ethics, Shelly Kagan Introduction to Marx and Engels: A Critical Reconstruction, Second Edition, Richard Schmitt Political Philosophy, Jean Hampton Philosophy of Mind, Jaegwon Kim Philosophy of Social Science, Second Edition, Alexander Rosenberg Philosophy of Education, Nel Noddings Philosophy of Law: An Introduction to Jurisprudence, Revised Edition, Jeffrie G. Murphy and Jules L. Coleman FORTHCOMING Metaphysics, Second Edition, Peter van Inwagen Theory of Knowledge, Second Edition, Keith Lehrer Philosophy of Physics, Revised Edition, Lawrence Sklar Philosophy of Cognitive Science, edited by Barbara Von Eckardt -iv- PHILOSOPHY OF BIOLOGY SECOND EDITION Elliott Sober UNIVERSITY OF WISCONSIN-MADISON Westview PRESS A Member of the Perseus Books Group -v- Dimensions of Philosophy Series All rights reserved. Printed in the United States of America. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system, without permission in writing from the publisher. Copyright © 2000 by Westview Press, A Member of the Perseus Books Group Published in 2000 in the United States of America by Westview Press, 5500 Central Avenue, Boulder, Colorado 80301-2877, and in the United Kingdom by Westview Press, 12 Hid's Copse Road, Cumnor Hill, Oxford OX2 9JJ Find us on the World Wide Web at www.westviewpress.com Library of Congress Cataloging-in-Publication Data Sober, Elliott. Philosophy of biology / Elliott Sober. -- 2nd ed. p. cm. -- (Dimensions of philosophy series) Includes bibliographical references and index. ISBN 0-8133-9126-1 (pbk.) 1. Evolution (Biology)--Philosophy. 2. Creationism. 3. Natural selection--Philosophy. 4. Evolution (Biology)--Religious aspect--Christianity. I. Title. II. Series. QH360.5.S63 1999 578′.01--dc21 99-049091 The paper used in this publication meets the requirements of the American National Standard for Permanence of Paper for Printed Library Materials Z39.48-1984. 10 9 8 7 6 5 4 3 2 1 -vi- For Sam -vii- [This page intentionally left blank.] -viii- CONTENTS List of Boxes and Figures xi Acknowledgments xiii Introduction xv 1 What Is Evolutionary Theory? 1 1.1 What Is Evolution? 1 1.2 The Place of Evolutionary Theory in Biology , 5 1.3 Pattern and Process , 7 1.4 Historical Particulars and General Laws , 14 1.5 The Causes of Evolution , 18 1.6 The Domains of Biology and Physics , 22 1.7 Biological Explanations and Physical Explanations , 25 Suggestions for Further Reading , 26 2 Creationism 27 2.1 The Danger of Anachronism , 27 2.2 Paley's Watch and the Likelihood Principle , 30 2.3 Hume's Critique , 33 2.4 Why Natural Selection Isdt a Random Process , 36 2.5 Two Kinds of Similarity , 39 2.6 The Problem of Predictive Equivalence , 42 2.7 Is the Design Hypothesis Unscientific? 46 2.8 The Incompleteness of Science , 55 Suggestions for Further Reading , 57 3 Fitness 58 3.1 An Idealized Life Cycle , 58 3.2 The Interpretation of Probability , 61 3.3 Two Ways to Find Out About Fitness , 68 3.4 The Tautology Problem , 70 3.5 Supervenience , 74 3.6 Advantageousness and Fitness , 78 -ix- 3.7 Teleology Naturalized , 83 Suggestions for Further Reading , 88 4 The Units of Selection Problem 89 4.1 Hierarchy , 89 4.2 Adaptation and Fortuitous Benefit , 96 4.3 Decoupling Parts and Wholes , 100 4.4 Red Herrings , 102 4.5 Examples , 108 4.6 Correlation, Cost, and Benefit , 111 Suggestions for Further Reading , 119 5 Adaptationism 121 5.1 What Is Adaptationism? 121 5.2 How Genetics Can Get in the Way , 125 5.3 Is Adaptationism Untestable? 130 5.4 The Argument from Complex Traits , 132 5.5 If Optimality Models Are Too Easy to Produce, Let's Make Them Harder , 133 5.6 Game Theory , 138 Suggestions for Further Reading , 145 6 Systematics 146 6.1 The Death of Essentialism , 148 6.2 Individuality and the Species Problem , 152 6.3 Three Systematic Philosophies , 162 6.4 Internal Coherence , 169 6.5 Phylogenetic Inference Based on Overall Similarity , 172 6.6 Parsimony and Phylogenetic Inference , 176 Suggestions for Further Reading , 187 7 Sociobiology and the Extension of Evolutionary Theory 188 7.1 Biological Determinism , 189 7.2 Does Sociobiology Have an Ideological Function? 198 7.3 Anthropomorphism Versus Linguistic Puritanism , 201 7.4 Ethics , 206 7.5 Models of Cultural Evolution , 213 Suggestions for Further Reading , 220 References 221 Index 231 -x- BOXES AND FIGURES Boxes 1.1 Definitions 6 1.2 How Versus Why 8 1.3 Fisher's Sex Ratio Argument 17 2.1 Popper's Asymmetry 50 2.2 The Virtue of Vulnerability 52 3.1 Quine on A Priori Truth 72 3.2 Reduction 80 3.3 Correlation 81 3.4 Hitchhiking and Intelligence 82 4.1 Simpson's Paradox 103 4.2 Junk DNA 109 4.3 The Prisoners' Dilemma 113 4.4 Kin Selection with a Dominant Gene for Altruism 114 5.1 The Two-Horn Rhinoceros Problem 125 5.2 The Flagpole Problem 139 6.1 Monophyly and the Species Problem 166 6.2 "Defining" Monophyletic Groups 182 6.3 Pattern Cladism 186 7.1 The Ought-Implies-Can Principle 199 7.2 Incest 204 Figures 1.1 Heritability 10 1.2 Anagenesis and cladogenesis 12 -xi- 1.3 A double heterozygote undergoing recombination by crossing over 19 1.4 Gamete formation without recombination 20 1.5 Sources and causes in evolutionary theory 22 1.6 Physicalism, vitalism, dualism 23 4.1 A case of evolution in which average fitness increases 97 4.2 A case of evolution in which average fitness remains constant 98 4.3 A case of evolution in which average fitness declines 99 4.4 The Weismann doctrine 104 4.5 Tit-for-Tat versus Always Defect 119 5.1 A case in which the fittest genotype must evolve 127 5.2 A case in which the fittest genotype cannot evolve 128 5.3 A case in which the fittest genotype can evolve 129 5.4 Size differences between the sexes and sex ratios in breeding groups 135 5.5 An optimality model for dung fly copulation time 137 5.6 The Hawk/Dove game 141 6.1 A pure branching process 164 6.2 A reticulating process 165 6.3 Examples of conflict between phenetic and cladistic principles 166 6.4 Homology and homoplasy 167 6.5 The assumption of uniform rates 173 6.6 Sparrows and robins: homology and homoplasy 177 6.7 Sparrows and robins: derived similarity 178 6.8 Lizards and crocodiles: ancestral similarity 180 6.9 The method of outgroup comparison 181 6.10 Transition probabilities for character change in a phylogenetic tree 185 7.1 Possible differences between the sexes concerning time devoted to child care 196 7.2 Incest avoidance 203 7.3 Homology, functionally similar homoplasy, and functionally dissimilar homoplasy 205 7.4 Cultural and biological evolution: three models 215 -xii- ACKNOWLEDGMENTS Robert Boyd, Robert Brandon, David Hull, Robert Jeanne, Philip Kitcher, John Maynard Smith, Robert O'Hara, Steven Hecht Orzack, Peter Richerson, Louise Robbins, Robert Rossi, Michael Ruse, Kim Sterelny, and David Sloan Wilson gave me plenty of useful advice on how earlier drafts of this book could be improved. I am very grateful to them for their help. I also want to thank Peter Godfrey-Smith, Richard Lewontin, Mohan Matthen, Anthony Peressini, Chris Stephens, and Steve Wykstra for their helpful suggestions for this second edition. I have reprinted material in Chapter 5 from an article I coauthored with Steven Hecht Orzack , "Optimality Models and the Long-Run Test of Adaptationism" ( American Naturalist, 1994, 143: 361-380). Chapter 4 contains passages from my essay "The Evolution of Altruism: Correlation, Cost, and Benefit" ( Biology and Philosophy, 1992, 7: 177-187, copyright © 1992 by Kluwer Academic Publishers; reprinted by permission of Kluwer Academic Publishers). In Chapter 7, I have used portions of my essays "Models of Cultural Evolution" (in P. Griffiths, ed., Trees of Life, 1991, pp. 17-39, copyright © 1991 by Kluwer Academic Publishers; reprinted by permission of Kluwer Academic Publishers) and "When Biology and Culture Conflict" (in H. Rolston III, ed., Biology, Ethics, and the Origins of Life, forthcoming). I thank my coauthor and the editors and publishers for permitting me to use these passages. Elliott Sober -xiii- [This page intentionally left blank.] -xiv- INTRODUCTION This book concentrates on philosophical problems raised by the theory of evolution. Chapter 1 describes some of the main features of that theory. What is evolution? What are the principal elements of the theory that Charles Darwin proposed and that subsequent biology has elaborated? How is evolutionary biology divided into subdisciplines? How is evolutionary theory related to the rest of biology and to the subject matter of physics? After this preliminary chapter (some of whose themes are taken up later), the book is divided into three unequal parts. The first concerns the threat from without. Creationists have challenged the theory of evolution by natural selection and have defended the idea that at least some important evolutionary events are due to intelligent design.