Originally published as the central chapter in the late author's critically acclaimed study, The Structure of Evolutionary Theory, a critical challenge to a core tenet of Darwin's theory of evolution explores the nature of biological change and its influence on evolutionary patterns and processes. Original. In 1972 Gould took the scientific world by storm with a paper on punctuated equilibrium that launched the controversial idea that the majority of species originate in geological moments (punctuations) and persist in stasis. Here he offers a book-length testament on a theory he fiercely promoted, repeatedly refined, and tirelessly defended. INTRODUCTION 1 1 WHAT EVERY PALEONTOLOGIST KNOWS 14 An Introductory Example 14 Testimonials to Common Knowledge 20 Darwinian Solutions and Paradoxes 26 The Paradox of Insulation from Disproof 30 The Paradox of Stymied Practice 33 2 THE PRIMARY CLAIMS OF PUNCTUATED EQUILIBRIUM 39 Data and Definitions 39 Microevolutionary Links 49 Macroevolutionary Implications 57 Tempo and the Significance of Stasis 59 Mode and the Speciational Foundation of Macroevolution 60 3 THE SCIENTIFIC DEBATE ON PUNCTUATED EQUILIBRIUM: CRITIQUES AND RESPONSES 62 Critiques Based on the Definability of Paleontological Species 62 Empirical Affirmation 62 Reasons for a Potential Systematic Underestimation of Biospecies by Paleospecies 68 Reasons for a Potential Systematic Overestimation of Biospecies by Paleospecies 72 Reasons Why an Observed Punctuational Pattern Might Not Represent Speciation 73 Critiques Based on Denying Events of Speciation as the Primary Locus of Change 77 Critiques Based on Supposed Failures of Empirical Results to Affirm Predictions of Punctuated Equilibrium 84 Claims for Empirical Refutation by Cases 84 PHENOTYPES 84 GENOTYPES 94 Empirical Tests of Conformity with Models 96 4 SOURCES OF DATA FOR TESTING PUNCTUATED EQUILIBRIUM 109 Preamble 109 The Equilibrium in Punctuated Equilibrium: Quantitatively Documented Patterns of Stasis in Unbranched Segments of Lineages 111 The Punctuations of Punctuated Equilibrium: Tempo and Mode in the Origin of Paleospecies 129 The Inference of Cladogenesis by the Criterion of Ancestral Survival 130 The "Dissection" of Punctuations to Infer Both Existence and Modality 143 TIME 143 GEOGRAPHY 145 MORPHOMETRIC MODE 145 Proper and Adequate Tests of Relative Frequencies: The Strong Empirical Validation of Punctuated Equilibrium 147 The Indispensability of Data on Relative Frequencies 147 Relative Frequencies for Higher Taxa in Entire Biotas 149 Relative Frequencies for Entire Clades 161 Causal Clues from Differential Patterns of Relative Frequencies 167 5 THE BROADER IMPLICATIONS OF PUNCTUATED EQUILIBRIUM FOR EVOLUTIONARY THEORY AND GENERAL NOTIONS OF CHANGE 172 What Changes May Punctuated Equilibrium Instigate in Our Views about Evolutionary Mechanisms and the History of Life? 172 The Explanation and Broader Meaning of Stasis 172 FREQUENCY 173 GENERALITY 174 CAUSALITY 175 Punctuation, the Origin of New Macroevolutionary Individuals, and Resulting Implications for Evolutionary Theory 185 TRENDS 186 THE SPECIATIONAL REFORMULATION OF MACROEVOLUTION 194 ECOLOGICAL AND HIGHER-LEVEL EXTENSIONS 222 Punctuation All the Way Up and Down? The Generalization and Broader Utility of Punctuated Equilibrium (in More Than a Metaphorical Sense) at Other Levels of Evolution, and for Other Disciplines In and Outside the Natural Sciences 229 General Models for Punctuated Equilibrium 229 Punctuational Change at Other Levels and Scales of Evolution 236 A PRELIMINARY NOTE ON HOMOLOGY AND ANALOGY IN THE CONCEPTUAL REALM 236 PUNCTUATION BELOW THE SPECIES LEVEL 240 PUNCTUATION ABOVE THE SPECIES LEVEL 245 Punctuational Models in Other Disciplines: Towards a General Theory of Change 265 PRINCIPLES FOR A CHOICE OF EXAMPLES 265 EXAMPLES FROM THE HISTORY OF HUMAN ARTIFACTS AND CULTURES 266 EXAMPLES FROM HUMAN INSTITUTIONS AND THEORIES ABOUT THE NATURAL WORLD 271 TWO CONCLUDING EXAMPLES, A GENERAL STATEMENT, AND A CODA 277 APPENDIX: A LARGELY SOCIOLOGICAL (AND FULLY PARTISAN) HISTORY OF THE IMPACT AND CRITIQUE OF PUNCTUATED EQUILIBRIUM 293 The Entrance of Punctuated Equilibrium into Common Language and General Culture 293 An Episodic History of Punctuated Equilibrium 301 Early Stages and Future Contexts 301 Creationist Misappropriation of Punctuated Equilibrium 309 Punctuated Equilibrium in Journalism and Textbooks 315 The Personal Aspect of Professional Reaction 325 The Case Ad Hominem against Punctuated Equilibrium 326 An Interlude on Sources of Error 338 The Wages of Jealousy 343 THE DESCENT TO NASTINESS 343 THE MOST UNKINDEST CUT OF ALL 349 THE WISDOM OF AGASSIZ'S AND VON BAER'S THREEFOLD HISTORY OF SCIENTIFIC IDEAS 352 A CODA ON THE KINDNESS AND GENEROSITY OF MOST COLLEAGUES 353 NOTES 357 BIBLIOGRAPHY 362 ILLUSTRATION CREDITS 382 INDEX 385