Eternal Ephemera: Adaptation and the Origin of Species from the Nineteenth Century through Punctuated Equilibria and Beyond

NOTES

In this section, I briefly cite some of the books, articles, manuscripts, and letters that either are discussed in the text or served as sources for my presentation of the specific contributions of the works of the scientists, philosophers, and historians who, in my opinion, were the most important shapers of evolutionary biology in general—and specifically of the taxic evolutionary perspective. Detailed citations of all these works are in the bibliography.

I also append some notes and reflections tied to the relevant portions of the text.

This book relies first and foremost on primary literature: it represents my considered understanding of what my predecessors and, in due course, my contemporaneous colleagues and my younger successors have to say about the evolutionary—especially taxic—issues discussed in the text. Perhaps the most difficult part of writing this narrative was trying to bring the same level of critical analysis to my own work as I sought to present for everyone else.

I am extremely grateful to Tom Baione, Mai Reitmeyer, and the entire staff of the library of the American Museum of Natural History—one of the great natural history libraries in the world—for all their help over the years. And I extend my thanks as well to the staff of the Rare Book Collection at Cambridge University Library for their hospitality and help when I read through Charles Darwin’s Geological Diary and Geological Notes under the superb guidance of historian David Kohn early in 2006.

Nowadays, much (but not all!) of the critically important works by not only Darwin but also his predecessors, contemporaries, and successors is freely available online. Specific Web sites are cited in the bibliography, but I will mention as well Google Books and Google Scholar as treasure troves whose riches increase seemingly on a daily basis.

Except where noted, all the many quoted passages throughout the text are taken directly from the original (or reprinted) sources.

INTRODUCTION

The thoughts on taxic versus transformational approaches developed in my lecture at the University of Rochester were an outgrowth of thinking about the ramifications of, as well as the spirited objections to, the notion of “punctuated equilibria,” as developed earlier in the 1970s (Eldredge 1971a; Eldredge and Gould 1972a, 1972b; Gould and Eldredge 1977). I remain grateful to colleagues H. B. Rollins and J. S. Schwartz for inviting me to participate in a symposium at the University of Pittsburgh, where I developed these thoughts further, leading to the publication of my paper “Alternative Approaches to Evolutionary Theory” (Eldredge 1979). All these papers (as well as many others of mine) can be found in downloadable format at www.NilesEldredge.com.

The voluminous notes, correspondence, and books by Charles Darwin relied on in this book are discussed in detail, and referenced, in chapters 2 and 3. Suffice it to say, at this point in the narrative, that the digital revolution has enabled Darwin historians such as David Kohn to publish scholarly transcriptions of many of Darwin’s notes and unpublished (in his lifetime) manuscripts; it is now even possible to download a complete edition of On the Origin of Species. The most important Web sites for accessing this treasure trove of Darwiniana are the Darwin Manuscripts Project (darwin.amnh.org) and the Darwin Correspondence Project (www.darwinproject.ac.uk).

The most influential, and generally excellent, biographies of Darwin in recent times are Janet Browne’s Charles Darwin: Voyaging (1995) and Charles Darwin: The Power of Place (2002), and Adrian Desmond and James Moore’s Darwin: The Life of a Tormented Evolutionist (1991).

1. THE ADVENT OF THE MODERN FAUNA

Baron Georges Cuvier (1769–1832) was a French zoologist and paleontologist, sometimes called the “Father of Comparative Anatomy.” Historian Martin Rudwick’s account of Cuvier and his works, Georges Cuvier, Fossil Bones, and Geological Catastrophes: New Translations and Interpretations of the Primary Texts (1997), remains the key resource on this important figure. Cuvier was a colleague of Jean-Baptiste Lamarck (1744–1829) at the Jardin des Plantes, the Parisian center for research on and exhibitions of France’s growing natural history collections. Although Cuvier was opposed to Lamarckian evolution, his influence on scientists such as Lamarck, Giambattista Brocchi, and Charles Darwin was enormous. Cuvier was a catastrophist, interpreting the fossil record of the history of life as showing numerous global extinction events, most of which he deemed to have been catastrophic, followed by the appearance, through unspecified means, of succeeding species. Cuvier established the reality of extinction to the satisfaction of most of his contemporaries. He published Recherches sur les ossemens fossiles de quadrupèdes in 1812; the “Preliminary Discourse” introducing that great work was widely read and was translated into English. Rudwick reports that Cuvier began pointing to the progressive “younging” of successions of species as early as 1812, in the “Preliminary Discourse.”

Robert Jameson (1774–1854), as we shall see in some detail in this chapter, was arguably the most important proponent of transmutational ideas in Great Britain in the 1820s. He was a geologist but also a physician on the faculty of the medical school in Edinburgh. His translation of Cuvier’s “Preliminary Discourse” into English was published as Essay on the Theory of the Earth. With Geological Illustrations by Professor Jameson (1813). Darwin took Jameson’s course on natural history and is known to have read the fifth edition of Essay on the Theory of the Earth (1827).

Charles Lyell (1797–1875), often considered the founder of modern geology, wrote the three-volume Principles of Geology (1830–1833). The impact of these works (especially, though by no means exclusively, volume 2 on transmutation) on the young Charles Darwin emerges especially in chapter 2 of this book. For convenience, I have relied heavily on a single-volume edition of Principles of Geology (1997) edited by historian James Secord, whose introduction on Lyell and the Principles is invaluable.

John Herschel’s letter to Lyell was published in Charles Babbage’s The Ninth Bridgewater Treatise (1838), but the passage had appeared in print earlier. Darwin’s exultant comment on the “mystery of mysteries” appears in Notebook E (1839) opposite page 58, on which is his succinct reduction of natural selection to three terse sentences.

Lyell specifically extols the importance and utility of focusing on fossil molluscan species to define the subdivisions, utilizing the collections of the French paleontologist Gérard Deshayes—but neither Lamarck’s nor Brocchi’s names appear in this section of Lyell’s text. According to Rudwick in Worlds Before Adam, some of the names of the subdivisions had actually been coined by William Whewell. See also William B. N. Berry’s informative Growth of a Prehistoric Time Scale (1968).

Brocchian Transmutation

I first encountered Brocchi’s name and core ideas in volume 2 of Lyell’s Principles of Geology. As discussed in chapter 2, Brocchi’s analogy is clearly present in Darwin’s essay “February 1835,” in the latter half of his Red Notebook (1836–1837), in some of his Transmutation Notebooks, and in an especially revelatory letter to Leonard Jenyns (Darwin 1844b)—with vestiges remaining in his “Pencil Sketch” (1842), his “Essay” (1844a), and On the Origin of Species (1859). Yet Darwin never cites Brocchi by name. I linked Brocchi to Darwin via Lyell in “Experimenting with Transmutation: Darwin, the Beagle, and Evolution” (Eldredge 2009a). Stefano Dominici and I investigated the paper trail linking Brocchi to Darwin in the literature, largely published in Edinburgh between 1816 and the late 1820s. We reported the results in “Brocchi, Darwin, and Transmutation: Phylogenetics and Paleontology at the Dawn of Evolutionary Biology” (Dominici and Eldredge 2010), the basis of the somewhat expanded account presented in this book.

Brocchi appears prominently in the two magnificent volumes by Martin Rudwick: Bursting the Limits of Time: The Reconstruction of Geohistory in the Age of Revolution (2005) and Worlds Before Adam: The Reconstruction of Geohistory in the Age of Reform (2008). In the former volume, Rudwick discusses Brocchi’s analogy, saying that it “respected the reality of species as discrete entities or natural kinds, rather than dissolving them in an endless flux of transmutation. It also suggested, though less explicitly, that the origin of species, might have an equally natural, yet episodic, mechanism, analogous to the birth of individuals” (527).

The descriptions of plant and animal species by the Swedish naturalist Carolus Linnaeus (born Karl von Linné) set the standards for modern systematic biology. Although he appeared to waver somewhat toward the end of his life, Linnaeus was not an evolutionist (transmutationist). One hundred and one years after Linnaeus published Systema naturae. Darwin, who essentially founded the modern science of evolutionary biology, published On the Origin of Species. The question that drives this section of my narrative becomes, then, what happened between 1758 and 1859? Specifically, when, where, and by whom was the pursuit of a non-miraculous causal explanation for the origin of modern species first developed?

The details of Darwin’s paleontological discoveries at Bahia Blanca in 1832 (and then again in 1833) are presented, with full citations, in chapter 2. The point here is that the early transmutationists such as Brocchi, Jameson (as we shall soon see), and Darwin used the persistence of genera—as opposed to the persistence of their component species—to broach the delicate subject of patterns of apparent births of descendant species from antecedent, congeneric species.

Robert Jameson, Robert Grant . . . and Charles Robert Darwin

Charles Darwin (1809–1882) wrote his Autobiography in 1876. According to his son Francis Darwin (1848–1925)—arguably the first of a still-growing horde of Darwin scholars, and the original editor of the Autobiography—Darwin intended his autobiographical sketch to be read only by members of his family. The version I have utilized was bundled with other Darwiniana by paleontologist George Gaylord Simpson and published as Charles Darwin’s Autobiography, with His Notes and Letters Depicting the Growth of the Origin of Species (Darwin [1876] 1950), while Darwin’s granddaughter Nora Barlow edited another edition, The Autobiography of Charles Darwin, 1809–1882 (1958).

The Edinburgh New Philosophical Journal has emerged as the hotbed of the publication of radical, transmutational thinking in Edinburgh—and thus in Great Britain. I was fortunate to discover that a complete run of these journals is housed in the library of the American Museum of Natural History, but they have yet to appear in their entirety on Internet sites such as Google Books.

Darwin’s student book list is available at the Darwin Correspondence Project (www.darwinproject.ac.uk).

2. DARWIN AND THE BEAGLE

Chapter 2 is devoted entirely to the nearly five years (1831–1836) of Charles Darwin’s experiences as naturalist and companion to Captain Robert FitzRoy on HMS Beagle, and to the relatively brief period on his arrival home when he was overtly (albeit to himself) developing a theory of transmutation from a primarily taxic perspective.

The account begins, substantively, with Darwin’s initial geological and paleontological observations and deductions on the Atlantic island of St. Jago (in the Cape Verde Islands) in early 1832. It ends with his letter to Leonard Jenyns, in which Darwin (1844b) makes it clear that it was Giambattista Brocchi’s analogy that first convinced him of transmutation.

The evidence is all in Darwin’s own handwriting. There are several distinct categories of Darwin’s manuscripts, books, letters, and notes that, together, yield the picture of his work on the Beagle expedition and shortly thereafter. I have (Eldredge 2009a; see also Dominici and Eldredge 2010) presented in abbreviated form my analysis based on the entire gamut of these documents:

• Correspondence. Darwin’s letters, especially, though not exclusively, to his mentor, John Stevens Henslow, reveal valuable insights into Darwin’s transmutational thinking while he was on the Beagle. Nora Barlow, Darwin’s granddaughter, edited a useful compendium of Darwin’s correspondence with Henslow: Darwin and Henslow: The Growth of an Idea (1967); a handy recent source is The ‘Beagle’ Letters (2008), edited by Frederick Burkhardt; and the correspondence is available at the Darwin Correspondence Project (www.darwinproject.ac.uk).

• Diary. Although the Diary that Darwin kept while on the Beagle is not particularly rich in purely scientific observations and conclusions, exceptions do occur—as in his mention of the snake at Bahia Blanca. Barlow edited and published Charles Darwin’s Diary of the Voyage of H.M.S. Beagle (1934), and Richard Keynes, Darwin’s great-grandson, edited another edition: Charles Darwin’s Beagle Diary (1988), which is rendered more valuable by occasional notes from what Keynes calls “The Down House Notebooks”: Darwin’s pocket-size Field Notebooks, in the collection at Down House, Kent, which have been edited and published by Gordon Chancellor and John van Wyhe as Charles Darwin’s Notebooks from the Voyage of the ‘Beagle’ (2009) and are available at Darwin Online (darwin-online.org.uk).

• Geological Diary/Geological Notes. These documents have yet to be fully published and, in any case, have never before been rigorously analyzed from a transmutational perspective for reasons discussed briefly in the text. The originals are in the Cambridge University Library; the portions most directly relevant to my text (those pertaining to South America) are catalogued as DAR 32–42. A transcription is available at Darwin Online (darwin-online.org.uk).

Historian Sandra Herbert is an exception to the generalization that scholars have almost completely ignored Darwin’s Geological Diary. Her book Charles Darwin, Geologist (2005) covers many aspects of Darwin’s geological work, including his paleontological experiences, especially in Patagonia. Herbert hints at the possible transmutational relevance of the Geological Diary, but stops short of concluding that it in fact shows the development of Darwin’s transmutational thinking while he was on the Beagle.

Two essays in the Earthquake Portfolio (DAR 42) are catalogued after the Geological Diary. The first of these is “Reflection on Reading my Geological Notes” (DAR 42:93–96), which Herbert has transcribed and analyzed in “From Charles Darwin’s Portfolio: An Early Essay on South American Geology and Species” (1995).

Herbert’s transcription and annotation of the Red Notebook—in The Red Notebook of Charles Darwin (1980) and “Red Notebook” (1987)—is also critical, as it represents the most explicit rendering of Darwin’s paleontological and zoological discoveries in South America in transmutational terms—albeit written some six months after his return to England.

The other, later essay in the Earthquake Portfolio is, along with Darwin’s paleontological experiences at Bahia Blanca in 1832 (with a return trip and ruminations a year later), the most important component of the Geological Diary/Geological Notes. Called simply “February 1835” (DAR 42:97–99), it has been transcribed and analyzed by historian M. J. S. Hodge in “Darwin and the Laws of the Animate Part of the Terrestrial System (1835–1837): On the Lyellian Origins of His Explanatory Program” (1983), and transcribed by David Kohn (Darwin Manuscripts Project, darwin.amnh.org).

• Zoological Notes. Keynes, himself a zoologist, did much to explicate his great-grandfather’s work—especially in the Beagle years. Charles Darwin’s Zoology Notes & Specimen Lists from H.M.S. Beagle (2000), edited by Keynes, does for the Zoological Notes (DAR 29–31) what remains to be done for the Geological Diary/Geological Notes: a lucid transcription accompanied by many notes and penetrating observations. It is available at Darwin Online (darwin-online.org.uk).

• Rewritten and compiled Zoological Notes: Animal Notes and Ornithological Notes. Toward the end of the Beagle voyage, Darwin organized and compiled much of his zoological data. Barlow transcribed and annotated Ornithological Notes (DAR 29.2) and published them as “Darwin’s Ornithological Notes” (1963), which is available at the Darwin Manuscript Project (darwin.amnh.org). Animal Notes (DAR 29.1:A1–19) can be found at Darwin Online (darwin-online.org.uk).

• Transmutation Notebooks (Notebooks B–E). Darwin’s Transmutation Notebooks (DAR 121–124), dealt with at the end of this chapter and in chapter 3, record the development of his transmutational thinking and, by Notebooks D and E, his change of emphasis from a taxic to a transformational perspective. They were written between 1837 and 1839. Embryologist and Darwin enthusiast Gavin de Beer published a version of these notebooks as “Darwin’s Notebooks on Transmutation of Species: Parts I–IV” (1960–1961) and, with M. J. Rowlands, “Darwin’s Notebooks on Transmutation of Species: Addenda and Corrigenda” (1960–1961), while the definitive transcription and scholarly annotation is by David Kohn: “Notebook B–Notebook E” (1987).

• Journal of Researches. In 1839, Darwin combined his Diary with his scientific observations into this monumental, informative, and downright delightful book, which has come to be known as The Voyage of the Beagle. The book summarizes his experiences in the field, with but a few hints of the transmutational thoughts that Darwin harbored. To disguise his ideas on the births and deaths of species through natural causes, as he compared his fossils with elements of the living South American fauna, Darwin developed his Law of Succession, which boils down simply to the taxic pattern of clearly related, endemic species replacing one another up through the stratigraphic record to modern times.

Yet Darwin, in the unanimous opinion of all Darwin scholars, was a convinced transmutationist at least by early 1837, based on evidence in the Red Notebook (as the text shows, I am convinced that he was at least taking a hard look at transmutation as early as 1832), and had discovered natural selection at least a year before The Voyage of the Beagle appeared. This disingenuous approach in public, in my opinion, is a mere extension of his secretive style developed in his notes while on the Beagle.

The second edition of Journal of Researches, with still more sly hints on evolution, appeared in 1845. Unlike the Diary, neither edition of the Voyage is to be taken as a literal sequential narrative of that journey: for example, Darwin does not reveal that his initial visit to Bahia Blanca—when he recovered his critically important fossils—actually occurred in 1832, not in 1833, when he returned for a second look. Readers of the Voyage will come away thinking that Darwin did not get to Bahia Blanca until 1833.

Bahia Blanca

The Fossils—and Shades of Giambattista Brocchi

George Gaylord Simpson’s first book Attending Marvels: A Patagonian Journal (1934) is a good adventure story—interspersing accounts of his paleontological experiences with vignettes of gunfire in the rebellious streets of Buenos Aires. Although he says little about evolution—and nothing about Darwin—in the pages of this book, Simpson does reveal his predilection for gradualist, transformational evolutionary thinking in several striking passages, discussed in “A Question of Individuality: Charles Darwin, George Gaylord Simpson, and Transitional Fossils” (Eldredge 2009b).

For an interesting recent look at Darwin’s (vertebrate) paleontological work in South America, and its relevance to the formation of Darwin’s evolutionary views, see Paul Brinkman’s “Charles Darwin’s Beagle Voyage, Fossil Vertebrate Succession, and ‘The Gradual Birth & Death of Species’” (2009).

In Journal of Researches (1839:209), Darwin, following Richard Owen’s identifications, changed the identification of the small rodent fossils found at Monte Hermoso from Cavia (the fossil and recent cavy species) to Ctenomys (the fossil and recent tucutucu species), using them as an example of his Law of Succession—and the probable source of Simpson’s grudging admission that these fossils may have played a role in the emergence of Darwin’s evolutionary thinking.

The portion of the Geological Notes dealing with the rocks and fossils at Bahia Blanca (Punta Alta and Monte Hermoso), as well as the notes from Darwin’s return trip in 1833 (labeled “Appendix”) are catalogued as DAR 32.1.61–74. All quotes in this section are from those pages.

Darwin and the Geographic Replacement of Closely Allied Species in Patagonia

In “Darwin’s Ornithological Notes” (1963:273–278), Nora Barlow follows up, closing with an appendix that is an even more comprehensive summary of Darwin’s writings on the rheas. She includes Darwin’s account of eating the specimen of the smaller, southern species of rhea shot for Christmas dinner—before he realized what it must be.

Crossing the Andes, Then on to the Galápagos

The bicentennial of Darwin’s birth in 2009 was marked, of course, by many lectures, symposia, articles, and books (even museum exhibitions!). One of the most useful is “Darwin en Argentina,” a special issue, available in English as well as Spanish, of the Revista de la Asociación Geológica Argentina (Aguirre-Urreta, Griffin, and Ramos 2009). Among many gems, there are accounts of Darwin’s trek across the Andes and of his work there and its relation to modern understanding of Andean uplift. The outcrops (including the newly discovered human and megafaunal footprint sites) at Bahia Blanca are also included in this wonderful compendium.

3. ENTER ADAPTATION AND THE CONFLICT BETWEEN ISOLATION AND GRADUAL ADAPTIVE CHANGE

It is tempting to think that Darwin was being a bit sarcastic, linking William Paley with Euclid as a source of “delight.” Yet Paley’s book was taken sufficiently seriously that, as I propose, his “argument from design” pretty much inhibited explanation of adaptations through natural causes for the first two or three decades of the nineteenth century.

Adaptation and Natural Selection in Speciation and Gradual Phyletic Change

David Kohn’s “Notebook B–Notebook E” (1987) is the source of all citations in this chapter. Given the large number of quoted passages in my text, I have inserted the numbers of the relevant Notebook page (not of Kohn’s transcription), directly in association with each quotation. Kohn’s introductory essay to each of the four Transmutation Notebooks serves as an invaluable consideration of the rich content of these notebooks, which more than any of Darwin’s other writings together reveal the order and logic underlying Darwin’s creation of the structure and content of his later two essays in the 1840s—“Pencil Sketch” (1842) and “Essay” (1844a)—and so, too, of the unfinished “Big Species Book” of the mid-1850s and, ultimately, of On the Origin of Species (1859) itself. I learned how to read Darwin’s handwriting by working with Kohn in the rare book room at the Cambridge University Library in 2006, reading Darwin’s Geological Notes and other manuscripts. Kohn is a master at deciphering Darwin’s handwriting, but in the transcription of the passage from page 155 of Notebook B, I beg to differ on one word: I read the word “spots” where Kohn has rendered it “sports.” Though either word is plausible, “spots” make more sense in this geographic context. The reader can judge by examining the image of this passage at the Darwin Manuscripts Project (darwin.amnh.org).

Darwin’s Evolutionary Texts

“Pencil Sketch”

Francis Darwin—Charles and Emma Darwin’s seventh child, and a noted zoologist in his own right—was arguably the first Darwin scholar of worth. In 1909, he published The Foundations of the Origin of Species: Two Essays Written in 1842 and 1844 in honor, simultaneously, of the hundredth anniversary of his father’s birth and the fiftieth anniversary of the publication of On the Origin of Species. The book consists of Francis Darwin’s transcriptions of the “Pencil Sketch” and the “Essay.”

These transcriptions, with a few editorial changes in the “Essay,” were republished under the editorship of embryologist Gavin de Beer, in Evolution by Natural Selection [by] Charles Darwin and Alfred Russel Wallace (Darwin 1958), and are available at Darwin Online (darwin-online.org.uk). I have relied on Francis Darwin’s transcription, as edited by de Beer (Darwin 1958), for the purposes of this narrative, and the page numbers for the quoted text refer to this edition. A new transcription, by Kohn, of these two manuscripts is available at the Darwin Manuscripts Project (darwin.amnh.org).

“Essay”

The “Fair Copy” of the manuscript of the “Essay” (Darwin 1844a) was written out by an amanuensis and intended, possibly, for future publication. Darwin made some annotations, including the important one singled out here, published as a footnote by Francis Darwin in 1909. To my knowledge not yet transcribed and published, the original is available at the Darwin Manuscripts Project (darwin.amnh.org).

Volume 1 of Alcide d’Orbigny’s (1802–1857) monumental Paléontologie française (1842) is dedicated to Jurassic cephalopods (mainly ammonoids) and is famous as his first articulation of the concept, and delimitation, of sequential étages in the Jurassic rocks of France and surrounding regions. The version consulted here, ironically, is Darwin’s very own copy, which is available at the Biodiversity Heritage Library (biodiversitylibrary.org/item/106856#page/7/mode/1up). For more on d’Orbigny’s life and work, see Marie-Thérèse Vénec-Peyré, “Beyond Frontiers and Time: The Scientific and Cultural Heritage of Alcide d’Orbigny (1802–1857)” (2004).

Darwin’s Principle of Divergence

In 1975, historian R. C. Stauffer published Charles Darwin’s Natural Selection: Being the Second Part of His Big Species Book Written from 1856 to 1858. The only published source of Darwin’s manuscript, which was not published in his lifetime, the book is available at Darwin Online (darwin-online.org.uk).

Darwin’s On the Origin of Species was, of course, first published in 1859. The sixth edition (1872) is important because it is the version that most subsequent readers had available to them, roughly until 1959—the centennial of the original publication of the Origin of Species. Evolutionary biologist Ernst Mayr wrote the introduction to a facsimile edition of the first edition, published in 1959. Both editions (plus others) are available at Darwin Online (darwin-online.org.uk) and the Darwin Manuscripts Project (darwin.amnh.org).

I have discussed all the texts, in a somewhat broader context than in this chapter narrative focusing on the taxic perspective in evolutionary biology, in Darwin: Discovering the Tree of Life (Eldredge 2005).

PART II. REBELLION AND REINVENTION

I find it deeply ironic that, until very recently, it was next to impossible for someone not affiliated with a university or another form of research institution to have access to most of the important early writings on evolutionary biology. Indeed, in some instances, such as Darwin’s early notes, one had to travel to the rare book room of Cambridge University Library and to Down House. All that has changed, as my text and the accompanying notes for the introduction and chapters 1 to 3 of this narrative have made clear: the Internet has made virtually everything of importance available to anyone with a computer and Internet service.

Not so, ironically, of the literature of the twenty and twenty-first centuries! To be sure, copies of Theodosius Dobzhansky’s, Ernst Mayr’s, and George Gaylord Simpson’s most important books are usually available, often at no great expense, through used book dealers.

That leaves scientific, historical, and philosophical papers published in technical journals. Some of these are available through “open access” platforms, such as all the back issues of Evolution: Education and Outreach, where Stefano Dominici’s “Brocchi’s Subapennine Fossil Conchology” (2010) and Dominici and Niles Eldredge’s “Brocchi, Darwin, and Transmutation: Phylogenetics and Paleontology at the Dawn of Evolutionary Biology” (2010), as well as other papers by me and other authors cited in the bibliography are freely available. But otherwise, and for the most part, one needs to have access to a major library to find articles published in such journals as Evolution, American Naturalist, Science, and Nature. Even though all of these journals are now archived and continuously available online, potential readers must be affiliated with institutions that provide access to archival organizations such as JSTOR. Otherwise, there is a hefty cost to download each pertinent article from the evolutionary literature from 1935 (where this narrative resumes) right down to the present moment.

I can but cite these papers and hope that readers can find them without too much difficulty.

4. SPECIES AND SPECIATION RECONSIDERED

In my opinion, Theodosius Dobzhansky’s “A Critique of the Species Concept in Biology” (1935), discussed extensively in this chapter, triggered the renaissance in taxic evolutionary thinking.

In Genetics and the Origin of Species (1937), Dobzhansky remarks that if this “maxim is taken too literally, it overshoots the mark,” as G. J. Romanes was apparently suggesting that adaptive change is indeed causally connected with speciation-in-isolation—the strong version of the importance of isolation in the generation of adaptive change that Darwin himself saw in the late 1830s, but later abandoned. Stephen Jay Gould and I teamed up in 1982 to bring out reprints of Dobzhansky’s Genetics and the Origin of Species (1937) and Ernst Mayr’s Systematics and the Origin of Species (1942). Gould wrote the editorial introduction to Dobzhansky’s book, while I did the same for Mayr’s.

The literature of modern studies of speciation is voluminous. For a recent review, and guidance to this literature, James Sobel and colleagues’ “The Biology of Speciation” (2009) provides a good start, as does Francesco Santini, Maria Pia Miglietta, and Anuschka Faucci’s “Speciation: Where Are We Now?” (2012). And I highly commend John N. Thompson’s Relentless Evolution (2013), which examines evolutionary processes, including speciation (especially “ecological speciation”) from the perspective of within- and among-genetic variation in environmental and geographic contexts.

5. PUNCTUATED EQUILIBRIA

When George Gaylord Simpson declined to include my editorial introduction to a reprint of Tempo and Mode in Evolution (1944), I can’t say that I was surprised, nor did I particularly hold it against him. I published it, instead, in Unfinished Synthesis: Biological Hierarchies and Modern Evolutionary Thought (Eldredge 1985b), along with my detailed examination of the three editions of Theodosius Dobzhansky’s Genetics and the Origin of Species (1937, 1941, 1951) and of Ernst Mayr’s Systematics and the Origin of Species (1942).

Simpson’s clarification of the ontological status of taxa and categories appeared in “The Meaning of Taxonomic Statements” (1963). In my opinion, this distinction is a perfect example of the sort of ontological analysis that Michael Ghiselin called for in his paper “A Radical Solution to the Species Problem” (1974), which is discussed in chapter 6.