Why Darwin rejected intelligent design

As a Cambridge University undergraduate Charles Darwin was fascinated and convinced by the argument for intelligent design, as set forth in William Paley’s 1802 classic, Natural Theology. Subsequently, during his five-year voyage on HMS Beagle (1831–1836), Darwin interpreted his biological findings through a creationist lens, including the thought-provoking evidence he encountered during his historic visit to the Galápagos Islands in September and October 1835. After his return to England in 1836 and his subsequent conversion to the idea of organic evolution in March 1837, Darwin searched for a theory that would explain both the fact of evolution and the widespread appearance of intelligent design. His insight into the process of natural selection, which occurred in September 1838, provided this alternative explanation. Darwin’s Origin of Species (1859) exemplifies his skillful deployment of the hypothetico-deductive method in testing and refuting the arguments for intelligent design that he had once so ardently admired.     

Darwin’s Sublime: The Contest Between Reason and Imagination in <Emphasis Type="Italic">On the Origin of Species</Emphasis>

Recent Darwin scholarship has provided grounds for recognising the Origin as a literary as well as a scientific achievement. While Darwin was an acute observer, a gifted experimentalist and indefatigable theorist, this essay argues that it was also crucial to his impact that the Origin transcended the putative divide between the scientific and the literary. Analysis of Darwin’s development as a writer between his journal-keeping on HMS Beagle and his construction of the Origin argues the latter draws on the pattern of the Romantic or Kantian sublime. The Origin repeatedly uses strategies which challenge the natural-theological appeal to the imagination in conceiving nature. Darwin’s sublime coaches the Origin’s readers into a position from which to envision nature that reduces and contains its otherwise overwhelming complexity. As such, it was Darwin’s literary achievement that enabled him to fashion a new ‘habit of looking at things in a given way’ that is the centrepiece of the scientific revolution bearing his name.     

Charles Darwin and the Origin of Life

When Charles Darwin published The Origin of Species 150 years ago he consciously avoided discussing the origin of life. However, analysis of some other texts written by Darwin, and of the correspondence he exchanged with friends and colleagues demonstrates that he took for granted the possibility of a natural emergence of the first life forms. As shown by notes from the pages he excised from his private notebooks, as early as 1837 Darwin was convinced that “the intimate relation of Life with laws of chemical combination, & the universality of latter render spontaneous generation not improbable”. Like many of his contemporaries, Darwin rejected the idea that putrefaction of preexisting organic compounds could lead to the appearance of organisms. Although he favored the possibility that life could appear by natural processes from simple inorganic compounds, his reluctance to discuss the issue resulted from his recognition that at the time it was possible to undertake the experimental study of the emergence of life.     

Darwin, Herschel, and the role of analogy in Darwin’s origin

In what follows, I consider the role of analogy in the first edition of Darwin’s Origin. I argue that Darwin follows Herschel’s methodology and hence exploits an analogy between artificial and natural selection that allows him generalize selection as a cause of evolutionary change. This argument strategy is not equivalent to an argument from analogy. Reading Darwin’s argument as conforming to Herschel’s two-step methodology of causal analysis followed by generalization allows us to understand the role and placement of Darwin’s discussion of artificial selection in the Origin, without making the mistake of portraying Darwin’s argument for the existence and character of natural selection as an analogical argument.     

The Preface to Darwin’s <Emphasis Type="Italic">Origin of Species</Emphasis>: The Curious History of the “Historical Sketch” *

Almost any modern reader’s first encounter with Darwin’s writing is likely to be the “Historical Sketch,” inserted by Darwin as a preface to an early edition of the Origin of Species, and having since then appeared as the preface to every edition after the second English edition. The Sketch was intended by him to serve as a short “history of opinion” on the species question before he presented his own theory in the Origin proper. But the provenance of the “Historical Sketch” is somewhat obscure. Some things are known about its production, such as when it first appeared and what changes were made to it between its first appearance in 1860 and its final form, for the fourth English edition, in 1866. But how it evolved in Darwin’s mind, why he wrote it at all, and what he thought he was accomplishing by prefacing it to the Origin remain questions that have not been carefully addressed in the scholarly literature on Darwin. I attempt to show that Darwin’s various statements about the “Historical Sketch,” made primarily to several of his correspondents between 1856 and 1860, are somewhat in conflict with one another, thus making problematic a satisfactory interpretation of how, when, and why the Sketch came to be. I also suggest some probable resolutions to the several difficulties. How Darwin came to settle on the title “Historical Sketch” for the Preface to the Origin is not certain, but a guess may be ventured. When he first submitted the text to Asa Gray in February 1860 he called it simply “Preface Contributed by the Author to this American Edition” (Burkhardt et al., eds., vol. 8, 1993, p. 572; the collected correspondence is hereafter cited as CCD). In fact he had thought of it as being properly called a Preface much earlier, perhaps as early as 1856, as will be seen in what follows. It came to be called “An Historical Sketch of the Recent Progress of Opinion on the Origin of Species” only in the third English edition, April 1861. This is the title it retained thereafter, with the exception of an addition to the title in the sixth English edition, “Previously to the Publication of the First Edition of this Work” (Peckham, 1959, pp. 20, 59). The word “sketch,” on the other hand was one of two words Darwin commonly used in private correspondence to refer to the book that would later become the Origin, the other word being “Abstract,” and both signifying that Darwin thought of the work as being a resume rather than a full-fledged study (e.g., letter to J.D. Hooker, May 9 1856, CCD vol. 6 p. 106; letter to Baden Powell January 18 1860, CCD vol. 8 p. 41; letter to Lyell 25 June 1858, CCD v. 7, 1991, pp. 117–8; letter to Lyell May 1856, CCD, v. 6 p. 100). The most likely source of the title “Historical Sketch” for Darwin’s Preface is Charles Lyell’s Principles of Geology in which, beginning with the third edition (1834), Lyell added titles to his chapters, calling chapters 2–4 “Historical Sketch of the Progress of Geology” (Secord, in Lyell [1997], p. xlvii; for other uses by Lyell of this expression, cf. Porter, 1976, p. 95; idem 1982, p. 38; and Lyell, 1830 [1990], p. 30). Further parallels between Lyell’s Introduction and Darwin’s “Historical Sketch” in terms of content and strategy are suggested below.     

Adaptations: Using Darwin's Origin to teach biology and writing

Charles Darwin's On the Origin of Species is at once familiar and unfamiliar. Everyone knows that the Origin introduced the world to the idea of evolution by natural selection, but few of us have actually read it. We suggest that it is worth taking the time not only to read what Darwin had to say, but also to use the Origin to teach both biology and writing. It provides scientific lessons in areas beyond evolutionary biology, such as ecology and biogeography. In addition, it provides valuable rhetorical lessons—how to construct an argument, write persuasively, make use of evidence, know your audience, and anticipate counterarguments. We have been using the Origin in various classes for several years, introducing new generations to Darwin, in his own words.     

Brocchi,Darwin, and Transmutation: Phylogenetics and Paleontology at the Dawn of Evolutionary Biology

Giambattista Brocchi’s (1814) monograph (see Dominici, Evo Edu Outreach, this issue, 2010) on the Tertiary fossils of the Subappenines in Italy—and their relation to the living molluscan fauna—contains a theoretical, transmutational perspective (“Brocchian transmutation”). Unlike Lamarck (1809), Brocchi saw species as discrete and fundamentally stable entities. Explicitly analogizing the births and deaths of species with those of individual organisms (“Brocchi’s analogy”), Brocchi proposed that species have inherent longevities, eventually dying of old age unless driven to extinction by external forces. As for individuals, births and deaths of species are understood to have natural causes; sequences of births and deaths of species produce genealogical lineages of descent, and faunas become increasingly modernized through time. Brocchi calculated that over 50% of his fossil species are still alive in the modern fauna. Brocchi’s work was reviewed by Horner (1816) in Edinburgh. Brocchi’s influence as a transmutational thinker is clear in Jameson’s (1827) “geological illustrations” in his fifth edition of his translation of Cuvier’s Theory of the Earth (read by his student Charles Darwin) and in the anonymous essays of 1826 and 1827 published in the Edinburgh New Philosophical Journal—which also carried a notice of Brocchi’s death in 1827. The notion that new species replace older, extinct ones—in what today would be called an explicitly phylogenetic context—permeates these essays. Herschel’s (1830) discussion of temporal replacement of species and the modernization of faunas closely mirrors these prior discussions. His book, dedicated to the search for natural causes of natural phenomena, was read by Charles Darwin while a student at Cambridge. Darwin’s work on HMS Beagle was in large measure an exploration of replacement patterns of “allied forms” of endemic species in time and in space. His earliest discussions of transmutation, in his essay February 1835, as well as the Red Notebook and the early pages of Notebook B (the latter two written in 1837 back in England), contain Brocchi’s analogy, including the idea of inherent species longevities. Darwin’s first theory of the origin of species was explicitly saltational, invoking geographic isolation as the main cause of the abrupt appearance of new species. We conclude that Darwin was testing the predicted patterns of both Brocchian and Lamarckian transmutation as early as 1832 at the outset of his work on the Beagle.     

Darwin teleologist? Design in the Orchids

Focusing on the Orchids, this article aims at disentangling the concepts of teleology, design and natural theology. It refers to several contemporary critics of Darwin (Kölliker, Argyll, Royer, Candolle, Delpino) to challenge Huxley's interpretation that Darwin's system was “a deathblow” to teleology. The Orchids seem rather to be a “flank-movement” (Gray): it departs from the Romantic theories of transmutation and the “imaginary examples” of the Origin; it focuses on empirical data and on teleological structures. Although Darwin refers to natural selection, his readers mock him for his fascination for delicate morphological contrivances and co-adaptations – a sign that he was inescapably lured to finality. Some even suggested that his system was a “theodicy”. In the history of Darwinism, the Orchids reveal “another” quite unexpected and heterodox Darwin: freed from the hypothetical fancies of the Origin, and even suggesting a new kind of physico-theology.     

Darwin,Wallace, and Huxley,and Vestiges of the Natural History of Creation

Conclusion Publication of the Vestiges and the rather primitive theory of evolution it expounded thus played a significant role in the careers of Darwin and Wallace. In addition, in spite of his poor opinion of the Vestiges, it presented Huxley with a convenient topic for critical discussion and the opportunity to focus more attention on the subject of evolution. The dynamic interactions among these leading figures of nineteenth-century natural science helped spur the development of more sophisticated models of evolution.Darwin had a proper appreciation of Chambers's contribution to evolutionary thought, although he fully recognized the shortcomings of this work. He understood the importance of allowing fresh ideas about organic change to be ventilated. However, he was primarily concerned with his own theory and viewed all developments in evolutionary biology from this perspective. If he did not give full consideration to Chambers and his book early on, it was due mainly to his feeling that the concepts in the Vestiges were very different from his own; he was therefore reluctant to embrace them as the forerunners of his own theory. As a scholar, he was also troubled by the scientific errors in the book. However, the record demonstrates that he attempted to make amends for any oversight on his part. His generous letter to Chambers's daughter, and his gracious treatment of Chambers during the brief time the latter lived in London, are ample proof of that.The attacks of Huxley, Sedgwick, and other prominent natural historians and geologists at the time, the problems inherent in Chambers's evolutionary theory, and the publication of the Origin, are the major reasons why the Vestiges became a neglected work. Nevertheless, Chambers's contribution will always stand out because, together with those of other late eighteenth- and early nineteenth-century predecessors of Darwin, it laid the foundations of modern evolutionary thought and, more importantly, helped prepare the scientific community for the more fully developed ideas of Darwin and Wallace.     

Darwin’s two theories, 1844 and 1859

Darwin’s first two, relatively complete, explicit articulations of his theorizing on evolution were his Essay of 1844 and On the Origin of Species published in 1859. A comparative analysis concludes that they espoused radically different theories despite exhibiting a continuity of strategy, much common structure and the same key idea. Both were theories of evolution by means of natural selection. In 1844, organic adaptation was confined to occasional intervals initiated and controlled by de-stabilization events. The modified descendants rebalanced the particular “plant and animal forms … unsettled by some alteration in their circumstances.” But by 1859, organic adaptation occurred continuously, potentially modifying the descendants of all organisms. Even natural selection, the persistent core of Darwin’s theorizing, does not prove to be a significant basis for theory similarity. Consequently, Darwin’s Origin theory cannot reasonably be considered as a mature version of the Essay. It is not a modification based on adjustments, further justifications and the integration of a Principle of Divergence. The Origin announced a new “scientific paradigm” while the Essay did little more than seemingly misconfigure the operation of a novel mechanism to extend varieties beyond their accepted bounds, and into the realm of possible new species. Two other collections of Darwin’s theorizing are briefly considered: his extensive notes of the late 1830s and his contributions to the famous meeting of 1 July 1858. For very different reasons, neither constitutes a challenge to the basis for this comparative study. It is concluded that, in addition to the much-debated social pressures, an unacknowledged further reason why Darwin did not publish his theorizing until 1859, could have been down to his perceptive technical judgement: wisely, he held back from rushing to publish demonstrably flawed theorizing.     

The Darwinian Revolution,as seen in 1979 and as seen Twenty-Five Years Later in 2004

My book, The Darwinian Revolution gives an overview of the revolution as understood at the time of its writing (1979). It shows that many factors were involved, from straight science through philosophical methodology, and on to religious influences and challenges. Also of importance were social factors, not the least of which was the professionalization of science in Britain in the 19th century. Since the appearance of that book, new, significant factors have become apparent, and here I discuss some of the most important – especially the way in which evolution as an idea came into being as an epiphenomenon of the ideology of cultural progress; the (often tense) interaction between ideas of biological progress and the urge to professionalization, and of how this led to a delay in the full appreciation of what Charles Darwin had done in the Origin; and the ongoing divide between biological functionalists and biological formalists, a Kuhnian-type paradigm difference that persists across the Darwinian revolution.     

“A Great Complication of Circumstances” – Darwin and the Economy of Nature

In 1749, Linnaeus presided over the dissertation “Oeconomia Naturae,” which argued that each creature plays an important and particular role in nature’s economy. This phrase should be familiar to readers of Darwin, for he claims in the Origin that “all organic beings are striving, it may be said, to seize on each place in the economy of nature.” Many scholars have discussed the influence of political economy on Darwin’s ideas. In this paper, I take a different tack, showing that Darwin’s idea of an economy of nature stemmed from the views of earlier naturalists like Linnaeus and Lyell. I argue, in the first section of the paper, that Linnaeus’ idea of oeconomia naturae is derived from the idea of the animal economy, and that his idea of politia naturae is an extension of the idea of a politia civitatis. In the second part, I explore the use of the concept of stations in the work of De Candolle and Lyell – the precursor to Darwin’s concept of places. I show in the third part of the paper that the idea of places in an economy of nature is employed by Darwin at many key points in his thinking: his discussion of the Galapagos birds, his reading of Malthus, etc. Finally, in the last section, I demonstrate that the idea of a place in nature’s economy is essential to Darwin’s account of divergence. To tell his famous story of divergence and adaptation, Darwin needed the economy of nature.     

Humboldt,Darwin, and population

Conclusions I have attempted to clarify some of the pathways in the development of Darwin's thinking. The foregoing examples of influence by no means include all that can be found by comparing Darwin's writings with Humboldt's. However, the above examples seem adequate to show the nature and extent of this influence. It now seems clear that Humboldt not only, as had been previously known, inspired Darwin to make a voyage of exploration, but also provided him with his basic orientation concerning how and what to observe and how to write about it. An important part of what Darwin assimilated from Humboldt was an appreciation of population analysis as a tool for assessing the state of societies and of the benefits and hardships which these societies can expect to receive from the living world around them.Darwin exhibited in his Journal of Researches a casual interest in the economic and political conditions of the countries he visited, but these considerations were much less important to him than to Humboldt. Instead, Darwin, with the assistance of Lyell's Principles of Geology, shifted from Humboldt's largely economic framework to a biological one built around the species question. This shift led Darwin away from a consideration of how the population biology of animals was related to man's economy to focus instead upon how population biology fitted into the economy of nature.Humboldt's Personal Narrative served very well as a model for Darwin's Journal of Researches, thereby helping Darwin gain scientific eminence. The Journal of Researches, like virtually all of Humboldt's writings, was a contribution to scientific orthodoxy. But Darwin had, along the way, acquired an urge to do more than just add his building blocks to the orthodox scientific edifice. He decided to rearrange those blocks of knowledge into a different structure, and for that task neither Humboldt's Personal Narrative nor any other of his works could serve as a model. Humboldt had lacked the confidence which Darwin needed that biogeography and the origin of species could be understood. Humboldt had not explored very far the possible connections between biology and geology. Nor had he provided a general synthetic account of population biology. Had he done so, he might have been more explicit about the extent of his endorsement of Malthus. But even if he had, Humboldt's strong orientation toward cooperation would probably have inhibited his recognition of the importance of competition in nature.Lyell, who had also benefited from reading Humboldt, gave Darwin insights that were lacking in Humboldt's Personal Narrative. Lyell admirably demonstrated how stratigraphy, paleontology, biogeography, and population biology could be interrelated, and his reasons for doing so were essentially the same as Darwin's. Lyell's understanding of biogeography and ecology came from the writings of Augustin-Pyramus de Candolle as much as from Humboldt's, and from the former Lyell derived an appreciation for the importance of competition and also a confidence that the mysteries of biogeography could be explained.¹¹⁷ Furthermore, Lyell's discussion of all these subjects and also of evolution in his Principles of Geology is a good synthetic argument that was the ideal model for Darwin's greatest book.Darwin, having become convinced that species change through time, was able to synthesize in his mind the contributions which he had derived from the writings of Humboldt and Lyell as they applied to the species question. When Darwin wrote his Journal of Researches there were two large gaps in his thinking about evolution that bothered him—the mechanism of evolution and the causes of extinction. It was only after reading Malthus in 1838 that he realized, as Lyell had more or less pointed out, how important was competition in nature. He now had the general outlines for his theory, and in the 1845 abridged edition of his Journal, now retitled The Voyage of the Beagle, he inserted a fuller discussion of competition in nature which showed his awareness of its importance as an ecological factor.¹¹⁸ An abridged version of this paper was presented at the meeting of the History of Science Society in Washington, D.C., on 29 December 1969.     

Sawfly taxa (Hymenoptera,Symphyta) described by Edward Newman and Charles Healy

Type specimens of seven nominal species of sawfly described by Edward Newman and one by Charles Healy were studied. This material is housed in the Oxford University Museum of Natural History, United Kingdom. The following new synonymies are proposed (valid names in parentheses): Hartigia Schiødte, 1839 (Phylloecus Newman, 1838), Cephus helleri Taschenberg, 1871 (Phylloecus faunus Newman, 1838) and Euura gallae Newman, 1837 (Euura mucronata (Hartig, 1837)). The type species of Euura Newman, 1837 and Euura subgenus Gemmura E. L. Smith, 1968 belong to the same taxonomic species, Euura mucronata (Hartig, 1837), so that these genus group names become new synonyms. Lectotypes are designated for Phyllotoma tormentillae Healy, 1868, Fenusa ianthe Newman, 1837, Fenusa parviceps Newman, 1837, Selandria pallida Newman, 1837 and Phylloecus faunus Newman, 1838. 26 new combinations are proposed for species formerly placed in Hartigia and here transferred to Phylloecus, and 4 original combinations are re-instated as valid.     

mrpA (all1838), a gene involved in alkali and Na sensitivity, may also have a role in energy metabolism in the cyanobacterium Anabaena sp. strain PCC 7120

Anabaena sp. PCC7120 contains a gene, mrpA (all1838), which forms part of a seven gene-cluster (all1843–all1837) with significant sequence similarity to bacterial operons that putatively code for a multicomponent cation/proton antiporter involved in alkaline pH adaptation and salt resistance. We previously showed that growth and photosynthesis were inhibited in a strain mutated in mrpA, denoted as PHB11, particularly at alkaline pH. Here, we show that respiration was also impaired in the mutant independently of the external pH. In addition, at high pH, less ATP and vegetative cell ferredoxin were present in PHB11, which also showed lower levels of ferredoxin-NADP⁺ oxidoreductase (FNR). Ferredoxin and FNR are involved in the generation of reductant NADPH in cyanobacteria. These results suggest an energetic role of mrpA (and perhaps of the whole mrp-gene cluster) in Anabaena sp. PCC 7120 that is further supported by the significant similarity of putative Anabaena Mrp proteins to membrane subunits of complex I.     

Charles Darwin’s <Emphasis Type="BoldItalic">Beagle</Emphasis> Voyage,Fossil Vertebrate Succession,and “The Gradual Birth &; Death of Species”

The prevailing view among historians of science holds that Charles Darwin became a convinced transmutationist only in the early spring of 1837, after his Beagle collections had been examined by expert British naturalists. With respect to the fossil vertebrate evidence, some historians believe that Darwin was incapable of seeing or understanding the transmutationist implications of his specimens without the help of Richard Owen. There is ample evidence, however, that he clearly recognized the similarities between several of the fossil vertebrates he collected and some of the extant fauna of South America before he returned to Britain. These comparisons, recorded in his correspondence, his diary and his notebooks during the voyage, were instances of a phenomenon that he later called the “law of the succession of types.” Moreover, on the Beagle, he was following a geological research agenda outlined in the second volume of Charles Lyell’s Principles of Geology, which implies that paleontological data alone could provide an insight into the laws which govern the appearance of new species. Since Darwin claims in On the Origin of Species that fossil vertebrate succession was one of the key lines of evidence that led him to question the fixity of species, it seems certain that he was seriously contemplating transmutation during the Beagle voyage. If so, historians of science need to reconsider both the role of Britain’s expert naturalists and the importance of the fossil vertebrate evidence in the development of Darwin’s ideas on transmutation.     

God and natural selection: The Darwinian idea of design

Conclusion If we arrange in chronological order the various statements Darwin made about God, creation, design, plan, law, and so forth, that I have discussed, there emerges a picture of a consistent development in Darwin's religious views from the orthodoxy of his youth to the agnosticism of his later years. Numerous sources attest that at the beginning of the Beagle voyage Darwin was more or less orthodox in religion and science alike.⁷⁸ After he became a transmutationist early in 1837, he concluded that the doctrine of secondary causes must be extented even to the history of life and that after the first forms of life were created, there was no further need for divine intervention, except where man was concerned. Man's body, he thought, was produced by the process of transmutation, but he believed for a time that man's soul was superadded. By mid-1838 he had become convinced that nothing, after the creation of life, was due to miracles. God works only through laws, which are capable of producing every effect of evey kind which surrounds us. The existence of man, the idea of God in man's mind, and the harmony of the whole system were in his eyes prearranged goals of deterministic laws imposed by God. Such a conception excludes the miracles on which Christianity depends; but it is not possible to say whether Darwin's loss of Christian faith, which occurred at about this same time, preceded and made possible his materialism or was rather caused or hastened by it.⁷⁹ In the weeks after his reading of Malthus, Darwin's belief in a plan of creation gave way to the belief that God created matter and life and designed their laws, leaving the details, however, to the workings of chance. This remained his view until the 1860s.There is no exact parallel between this development of Darwin's religious views and the development of his ideas on evolution, but there is a general correspondence. When he believed in a plan of creation, Darwin's theory of transmutation did not depend on struggle or the selection of chance variations. Adaptation was, for him, an automatic response to environmental chance. From late 1838 to 1859 he believed in designed laws and chance, and this belief, too, has its parallel in his theory. The element of chance in natural selection meant that there could be no detailed plan,in which even man's idea of God would be a necessary outcome of nature's laws (man himself is not a necessary outcome of the working of natural selection).⁸⁰ But Darwin still believed nature was programmed to achieve certain general ends. We might say that he believed in a general, though not a special, teleology. Natural selection was for him a law to maximize utility, creating useful organs, retaining vestiges for future use. For many years it was a law designed to produce organisms perfectly adapted to their environments. Only later did Darwin come to doubt even this sort of design in nature.⁸¹ One way of describing the development of Darwin's evolutionary thought is to say that it shows a gradual abandoning of his theistic assumptions, so that by the late 1860s his theory was informed to a slighter extent by notions of purpose and design than it was in 1838 or 1844 or 1859.     

Experimenting with Transmutation: Darwin, the Beagle, and Evolution

Detailed analysis of Darwin’s scientific notes and other writings from the Beagle voyage reveals a focus on endemism and replacement of allied taxa in time and in space that began early in the journey. Though it is impossible to determine exactly when Darwin became a transmutationist, the evidence suggests that he was conversant with the transmutational ideas of Lamarck and others and testing (“experimenting” with) them—before he received a copy of Lyell’s Principles of Geology, vol. 2, in November 1832, in which Lyell describes and disputes Lamarck’s theory. To the two rhea species of Patagonia and the four mockingbird species of the Galapagos, we can now add the living Patagonian cavy (rodent) species, and its extinct putatively related species that Darwin collected at Monte Hermoso (Bahia Blanca) in the Fall of 1832, as a replacement pattern absolutely critical to the development of Darwin’s transmutational thinking. Darwin developed his first transmutational theory by adopting “Brocchi’s analogy” (Rudwick 2008)—i.e. that births and deaths of species are analogous to the births and deaths of individuals. Births and deaths of species, as of individuals, are thus explicable in terms of natural causes. Darwin explored these themes and the replacement of the extinct cavy by the modern species explicitly in his February 1835 essay (Darwin 1835a).