The Structure of Evolutionary Theory Read online

  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 922

  General Models for Punctuated Equilibrium 922

  Punctuational Change at Other Levels and Scales of Evolution 928

  A Preliminary Note on Homology and Analogy in the Conceptual Realm 928

  Punctuation Below the Species Level 931

  Punctuation Above the Species Level 936

  Stasis Analogs: Trending and Non-Trending in the Geological History of Clades 936

  Punctuational Analogs in Lineages: The Pace of Morphological Innovation 939

  Punctuational Analogs in Faunas and Ecosystems 946

  Punctuational Models in Other Disciplines: Towards a General Theory of Change 952

  Principles for a Choice of Examples 952

  Examples from the History of Human Artifacts and Cultures 952

  Examples from Human Institutions and Theories about the Natural World 957

  [Page xviii]

  Two Concluding Examples, a General Statement, and a Coda 962

  • Appendix: A Largely Sociological (and Fully Partisan) History of the Impact and Critique of Punctuated Equilibrium 972

  The Entrance of Punctuated Equilibrium into Common Language and General Culture 972

  An Episodic History of Punctuated Equilibrium 979

  Early Stages and Future Contexts 979

  Creationist Misappropriation of Punctuated Equilibrium 986

  Punctuated Equilibrium in Journalism and Textbooks 990

  The Personal Aspect of Professional Reaction 999

  The Case Ad Hominem against Punctuated Equilibrium 1000

  An Interlude on Sources of Error 1010

  The Wages of Jealousy 1014

  The Descent to Nastiness 1014

  The Most Unkindest Cut of All 1019

  The Wisdom of Agassiz's and von Baer's Threefold History of Scientific Ideas 1021

  A Coda on the Kindness and Generosity of Most Colleagues 1022

  Chapter 10: The Integration of Constraint and Adaptation (Structure and Function) in Ontogeny and Phylogeny: Historical Constraints and the Evolution of Development 1025

  • Constraint as a Positive Concept 1025

  Two Kinds of Positivity 1025

  An Etymological Introduction 1025

  The First (Empirical) Positive Meaning of Channeling 1027

  The Second (Definitional) Positive Meaning of Causes outside Accepted Mechanisms 1032

  Heterochrony and Allometry as the Locus Classicus of the First Positive (Empirical) Meaning. Channeled Directionality by Constraint. 1037

  The Two Structural Themes of Internally Set Channels and Ease of Transformation as Potentially Synergistic with Functional Causality by Natural Selection: Increasing Shell Stability in the Gryphaea Heterochronocline 1040

  Ontogenetically Channeled Allometric Constraint as a Primary Basis of Expressed Evolutionary Variation: The Full Geographic and Morphological Range of Cerion uva 1045

  [Page xix]

  The Aptive Triangle and the Second Positive Meaning: Constraint as a Theory-Bound Term for Patterns and Directions Not Built Exclusively (Or Sometimes Even at All) by Natural Selection 1051

  The Model of the Aptive Triangle 1051

  Distinguishing and Sharpening the Two Great Questions 1053

  The Structural Vertex 1053

  The Historical Vertex 1055

  An Epitome for the Theory-Bound Nature of Constraint Terminology 1057

  • Deep Homology and Pervasive Parallelism: Historical Constraint as the Primary Gatekeeper and Guardian of Morphospace 1061

  A Historical and Conceptual Analysis of the Underappreciated Importance of Parallelism for Evolutionary Theory 1061

  A Context for Excitement 1061

  A Terminological Excursus on the Meaning of Parallelism 1069

  The Nine Fateful Little Words of E. Ray Lankester 1069

  The Terminological Origin and Debate about the Meaning and Utility of Parallelism 1076

  A Symphony in Four Movements on the Role of Historical Constraint in Evolution: Towards the Harmonious Rebalancing of Form and Function in Evolutionary Theory 1089

  Movement One, Statement: Deep Homology across Phyla: Mayr's Functional Certainty and Geoffroy's Structural Vindication 1089

  Deep Homology, Archetypal Theories, and Historical Constraint 1089

  Mehr Licht (More Light) on Goethe's Angiosperm Archetype 1092

  Hoxology and Geoffroy's First Archetypal Theory of Segmental Homology 1095

  An Epitome and Capsule History of Hoxology 1095

  Vertebrate Homologs in Structure and Action 1101

  Segmental Homologies of Arthropods and Vertebrates: Geoffroy's Vindication 1106

  Rediscovering the Vertebrate Rhombomeres 1107

  More Extensive Homologies throughout the Developing Somites 1109

  Some Caveats and Tentative Conclusions 1112

  Geoffrey's Second Archetypal Theory of Dorso-Ventral Inversion in the Common Bilaterian Groundplan 1117

  [Page xx]

  Movement Two, Elaboration: Parallelism of Underlying Generators: Deep Homology Builds Positive Channels of Constraint 1122

  Parallelism All the Way Down: Shining a Light and Feeding the Walk 1122

  Parallelism in the Large: Pax-6 and the Homology of Developmental Pathways in Homoplastic Eyes of Several Phyla 1123

  Data and Discovery 1123

  Theoretical Issues 1127

  A Question of Priority 1130

  Parallelism in the Small: The Origin of Crustacean Feeding Organs 1132

  Pharaonic Bricks and Corinthian Columns 1134

  Movement Three, Scherzo: Does Evolutionary Change Often Proceed by Saltation Down Channels of Historical Constraint? 1142

  Movement Four, Recapitulation and Summary: Early Establishment of Rules and the Inhomogenous Population of Morphospace: Dobzhansky's Landscape as Primarily Structural and Historical, Not Functional and Immediate 1147

  Bilaterian History as Top-Down by Tinkering of an Initial Set of Rules, Not Bottom-Up by Adding Increments of Complexity 1147

  Setting of Historical Constraints in the Cambrian Explosion 1155

  Channeling the Subsequent Directions of Bilaterian History from the Inside 1161

  An Epilog on Dobzhansky's Landscape and the Dominant Role of Historical Constraint in the Clumped Population of Morphospace 1173

  Chapter 11: The Integration of Constraint and Adaptation (Structure and Function) in Ontogeny and Phylogeny: Structural Constraints, Spandrels, and the Centrality of Exaptation in Macroevolution 1179

  • The Timeless Physics of Evolved Function 1179

  Structuralism's Odd Man Outside 1179

  D'Arcy Thompson's Science of Form 1182

  The Structure of an Argument 1182

  The Tactic and Application of an Argument 1189

  The Admitted Limitation and Ultimate Failure of an Argument 1196

  [Page xxi]

  Odd Man In (D'Arcy Thompson's Structuralist Critique of Darwinism) and Odd Man Out (His Disparagement of Historicism) 1200

  An Epilog to an Argument 1207

  Order for Free and Realms of Relevance for Thompsonian Structuralism 1208

  • Exapting the Rich and Inevitable Spandrels of History 1214

  Nietzsche's Most Important Proposition of Historical Method 1214

  Exaptation and the Principle of Quirky Functional Shift: The Restricted Darwinian Version as the Ground of Contingency 1218

  How Darwin Resolved Mivart's Challenge of Incipient Stages 1218

  The Two Great Historical and Structural Implications of Quirky Functional Shift 1224

  How Exaptation Completes and Rationalizes the Terminology of Evolutionary Change by Functional Shifting 1229

  Key Criteria and Examples of Exaptation 1234

  The Complete Version, Replete with Spandrels
: Exaptation and the Terminology of Nonadaptative Origin 1246

  The More Radical Category of Exapted Features with Truly Nonadaptive Origins as Structural Constraints 1246

  Defining and Defending Spandrels: A Revisit to San Marco 1249

  Three Major Reasons for the Centrality of Spandrels, and Therefore of Nonadaptation, in Evolutionary Theory 1258

  • The Exaptive Pool: The Proper Conceptual Formula and Ground of Evolvability 1270

  Resolving the Paradox of Evolvability and Defining the Exaptive Pool 1270

  The Taxonomy of the Exaptive Pool 1277

  Franklins and Miltons, or Inherent Potentials vs. Available Things 1277

  Choosing a Fundamentum Divisionis for a Taxonomy: An Apparently Arcane and Linguistic Matter That Actually Embodies a Central Scientific Decision 1280

  Cross-Level Effects as Miltonic Spandrels, Not Franklinian Potentials: The Nub of Integration and Radical Importance 1286

  A Closing Comment to Resolve the Macroevolutionary Paradox that Constraint Ensures Flexibility Whereas Selection Crafts Restriction 1294

  [Page xxii]

  Chapter 12: Tiers of Time and Trials of Extrapolationism, With an Epilog on the Interaction of General Theory and Contingent History 1296

  • Failure of Extrapolationism in the Non-Isotropy of Time and Geology 1296

  The Specter of Catastrophic Mass Extinction: Darwin to Chicxulub 1296

  The Paradox of the First Tier: Towards a General Theory of Tiers of Time 1320

  • An Epilog on Theory and History in Creating the Grandeur of This View of Life 1332

  Bibliography 1344

  Illustration Credits 1388

  Index 1393

  About This P2P ePub Edition

  [Page 1]

  CHAPTER ONE

  Defining and Revising

  the Structure of Evolutionary Theory

  Theories Need Both Essences and Histories

  In a famous passage added to later editions of the Origin of Species, Charles Darwin (1872, p. 134) generalized his opening statement on the apparent ab­surdity of evolving a complex eye through a long series of gradual steps by re­minding his readers that they should always treat “obvious” truths with skepticism. In so doing, Darwin also challenged the celebrated definition of science as “organized common sense,” as championed by his dear friend Thomas Henry Huxley. Darwin wrote: “When it was first said that the sun stood still and world turned round, the common sense of mankind declared the doctrine false; but the old saying of Vox populi, vox Dei [the voice of the people is the voice of God], as every philosopher knows, cannot be trusted in science.”

  Despite his firm residence within England's higher social classes, Darwin took a fully egalitarian approach towards sources of expertise, knowing full well that the most dependable data on behavior and breeding of domesticated and cultivated organisms would be obtained from active farmers and hus­bandmen, not from lords of their manors or authors of theoretical treatises. As Ghiselin (1969) so cogently stated, Darwin maintained an uncompromis­ingly “aristocratic” set of values towards judgment of his work — that is, he cared not a whit for the outpourings of vox populi, but fretted endlessly and fearfully about the opinions of a very few key people blessed with the rare mix of intelligence, zeal, and attentive practice that we call expertise (a demo­cratic human property, respecting only the requisite mental skills and emo­tional toughness, and bearing no intrinsic correlation to class, profession or any other fortuity of social circumstance).

  Darwin ranked Hugh Falconer, the Scottish surgeon, paleontologist, and Indian tea grower, within this most discriminating of all his social groups, a panel that included Hooker, Huxley and Lyell as the most prominent mem­bers. Thus, when Falconer wrote his important 1863 paper on American fos­sil elephants (see Chapter 9, pages 745–749, for full discussion of this inci­dent), Darwin flooded himself with anticipatory fear, but then rejoiced in his critic's generally favorable reception of evolution, as embodied in the closing [Page 2] sentence of Falconer's key section: “Darwin has, beyond all his cotemporaries [sic], given an impulse to the philosophical investigation of the most back­ward and obscure branch of the Biological Sciences of his day; he has laid the foundations of a great edifice; but he need not be surprised if, in the progress of erection, the superstructure is altered by his successors, like the Duomo of Milan, from the roman to a different style of architecture.”

  In a letter to Falconer on October 1, 1862 (in F. Darwin, 1903, volume 1, p. 206), Darwin explicitly addressed this passage in Falconer's text. (Darwin had received an advance copy of the manuscript, along with Falconer's re­quest for review and criticism — hence Darwin's reply, in 1862, to a text not printed until the following year): “To return to your concluding sentence: far from being surprised, I look at it as absolutely certain that very much in the Origin will be proved rubbish; but I expect and hope that the framework will stand.”

  The statement that God (or the Devil, in some versions) dwells in the de­tails must rank among the most widely cited intellectual witticisms of our time. As with many clever epigrams that spark the reaction “I wish I'd said that!”, attribution of authorship tends to drift towards appropriate famous sources. (Virtually any nifty evolutionary saying eventually migrates to Т. Н. Huxley, just as vernacular commentary about modern America moves to­wards Mr. Berra.) The apostle of modernism in architecture, Ludwig Mies van der Rohe, may, or may not, have said that “God dwells in the details,” but the plethora of tiny and subtle choices that distinguish the elegance of his great buildings from the utter drabness of superficially similar glass boxes throughout the world surely validates his candidacy for an optimal linkage of word and deed.

  Architecture may assert a more concrete claim, but nothing beats the extraordinary subtlety of language as a medium for expressing the importance of apparently trivial details. The architectural metaphors of Milan's cathe­dral, used by both Falconer and Darwin, may strike us as effectively identical at first read. Falconer says that the foundations will persist as Darwin's leg­acy, but that the superstructure will probably be reconstructed in a quite dif­ferent style. Darwin responds by acknowledging Falconer's conjecture that the theory of natural selection will undergo substantial change; indeed, in his characteristically diffident way, Darwin even professes himself “absolutely certain” that much of the Origin's content will be exposed as “rubbish.” But he then states not only a hope, but also an expectation, that the “framework” will stand.

  We might easily read this correspondence too casually as a polite dialogue between friends, airing a few unimportant disagreements amidst a commit­ment to mutual support. But I think that this exchange between Falconer and Darwin includes a far more “edgy” quality beneath its diplomacy. Consider the different predictions that flow from the disparate metaphors chosen by each author for the Duomo of Milan — Falconer's “foundation” vs. Darwin's “framework.” After all, a foundation is an invisible system of support, sunk into the ground, and intended as protection against sinking or toppling of the [Page 3] overlying public structure. A framework, on the other hand, defines the basic form and outline of the public structure itself. Thus, the two men conjure up very different pictures in their crystal balls. Falconer expects that the underly­ing evolutionary principle of descent with modification will persist as a fac­tual foundation for forthcoming theories devised to explain the genealogical tree of life. Darwin counters that the theory of natural selection will persist as a basic explanation of evolution, — even though many details, and even some subsidiary generalities, cited within the Origin will later be rejected as false, or even illogical.

  I stress this distinction, so verbally and disarmingly trivial at a first and superficial skim through Falconer's and Darwin's words, but so incisive and portentous as contrasting predictions about the history of evolutionary the­ory, because my own position — closer to Falconer than to Darwin, but in ac­cord with Darwin on one key point — led me to write th
is book, while also supplying the organizing principle for the “one long argument” of its entirety. I do believe that the Darwinian framework, and not just the foundation, per­sists in the emerging structure of a more adequate evolutionary theory. But I also hold, with Falconer, that substantial changes, introduced during the last half of the 20th century, have built a structure so expanded beyond the origi­nal Darwinian core, and so enlarged by new principles of macroevolutionary explanation, that the full exposition, while remaining within the domain of Darwinian logic, must be construed as basically different from the canonical theory of natural selection, rather than simply extended.

  A closer study of the material basis for Falconer and Darwin's metaphors — the Duomo (or Cathedral) of Milan — might help to clarify this important distinction. As with so many buildings of such size, expense, and centrality (both geographically and spiritually), the construction of the Duomo occupied sev­eral centuries and included an amalgam of radically changing styles and pur­poses. Construction began at the chevet, or eastern end, of the cathedral in the late 14th century. The tall windows of the chevet, with their glorious flamboyant tracery, strike me as the finest achievement of the entire structure, and as the greatest artistic expression of this highly ornamented latest Gothic style. (The term “flamboyant” literally refers to the flame-shaped element so extensively used in the tracery, but the word then came to mean “richly deco­rated” and “showy,” initially as an apt description of the overall style, but then extended to the more general meaning used today.)

  Coming now to the main point, construction then slowed considerably, and the main western facade and entrance way (Fig. 1-1) dates from the late 16th century, when stylistic preferences had changed drastically from the points, curves and traceries of Gothic to the orthogonal, low-angled or gently rounded lintels and pediments of classical Baroque preferences. Thus, the first two tiers of the main (western) entrance to the Duomo display a style that, in one sense, could not be more formally discordant with Gothic elements of de­sign, but that somehow became integrated into an interesting coherence. (The third tier of the western facade, built much later, returned to a “retro” Gothic style, thus suggesting a metaphorical reversal of phylogenetic conventions, as