The meaning of Darwin's 'abominable mystery'

Charles Darwin's "abominable mystery" has come to symbolize just about all aspects of the origin and early evolution of flowering plants. Yet, there has never been an analysis of precisely what Darwin thought was so abominably mysterious. Here I explicate Darwin's thoughts and frustrations with the fossil record of flowering plants as revealed in correspondence with Joseph Hooker, Gaston de Saporta, and Oswald Heer between 1875 and 1881. I also examine the essay by John Ball that prompted Darwin to write his "abominable mystery" letter to Hooker in July of 1879. Contrary to what is generally believed, Darwin's abominable mystery has little if anything to do with the fossil prehistory of angiosperms, identification of the closest relatives of flowering plants, questions of the homologies (and character transformations) of defining features of flowering plants, or the phylogeny of flowering plants themselves. Darwin's abominable mystery and his abiding interest in the radiation of angiosperms were never driven primarily by a need to understand the literal text of the evolutionary history of flowering plants. Rather, Darwin was deeply bothered by what he perceived to be an abrupt origin and highly accelerated rate of diversification of flowering plants in the mid-Cretaceous. This led Darwin to create speculative arguments for a long, gradual, and undiscovered pre-Cretaceous history of flowering plants on a lost island or continent. Darwin also took refuge in the possibility that a rapid diversification of flowering plants in the mid-Cretaceous might, if real, have a biological explanation involving coevolutionary interactions between pollinating insects and angiosperms. Nevertheless, although generations of plant biologists have seized upon Darwin's abominable mystery as a metaphor for their struggle to understand angiosperm history, the evidence strongly suggests that the abominable mystery is not about angiosperms per se. On the contrary, Darwin's abominable mystery is about his abhorrence that evolution could be both rapid and potentially even saltational. Throughout the last years of his life, it just so happens that flowering plants, among all groups of organisms, presented Darwin with the most extreme exception to his strongly held notion natura non facit saltum, nature does not make a leap.     

Darwin on Aristotle

Charles Darwin's famous 1882 letter, in response to a gift by his friend, William Ogle of Ogle's recent translation of Aristotle's Parts of Animals, in which Darwin remarks that his “two gods,” Linnaeus and Cuvier, were “mere school-boys to old Aristotle,” has been thought to be only an extravagantly worded gesture of politeness. However, a close examination of this and other Darwin letters, and of references to Aristotle in Darwin's earlier work, shows that the famous letter was written several weeks after a first, polite letter of thanks, and was carefully formulated and literally meant. Indeed, it reflected an authentic, and substantial, increase in Darwin's already high respect for Aristotle, as a result of a careful reading both of Ogle's Introduction and of more or less the portion of Ogle's translation which Darwin says he has read. Aristotle's promotion to the pantheon, as an examination of the basis for Darwin's admiration of Linnaeus and Cuvier suggests, was most likely the result specifically of Darwin's late discovery that the man he already knew as “one of the greatest ... observers that ever lived” (1879) was also the ancient equivalent both of the great modern systematist and of the great modern advocate of comparative functional explanation. It may also have reflected some real insight on Darwin's part into the teleological aspect of Aristotle's thought, indeed more insight than Ogle himself had achieved, as a portion of their correspondence reveals. This revised version was published online in July 2006 with corrections to the Cover Date.     

Adaptation and the origin of species

As reflected in the title of his masterwork On the Origin of Species, Darwin proposed that adaptation is the primary mechanism of speciation. On this, Darwin was criticized for his neglect of reproductive isolation, his lack of appreciation for the role of geographic barriers, his failure to distinguish varieties from species, and his typological species concept. Two developments since Darwin, the biological species concept of Ernst Mayr and the methods of Coyne and Orr for estimating the contribution of different barriers to the total reproductive isolation, provide a framework for reconciling Darwin's view on the primacy of adaptation in speciation with later proposals that emphasize reproductive isolation. A review of the few studies that have estimated the contributions of multiple isolating barriers suggests that habitat isolation and other barriers that operate before hybrid formation are much stronger than intrinsic postzygotic isolation. In light of these data, I suggest that Darwin's focus on adaptation in the origin of species was essentially correct, a conclusion that calls for future studies that explore the links between adaptation and speciation, in particular, ecogeographic isolating barriers that result from adaptive divergence in habitat use. The recent revival in thinking about ecological factors and adaptive divergence in the origin of species echoes Darwin's much-criticized "principle of divergence" and suggests that the emerging views from today's naturalists are not so different from those espoused by Darwin some 150 years ago.     

Darwin was a teleologist

It is often claimed that one of Darwin's chief accomplishments was to provide biology with a non-teleological explanation of adaptation. A number of Darwin's closest associates, however, and Darwin himself, did not see it that way. In order to assess whether Darwin's version of evolutionary theory does or does not employ teleological explanation, two of his botanical studies are examined. The result of this examination is that Darwin sees selection explanations of adaptations as teleological explanations. The confusion in the nineteenth century about Darwin's attitude to teleology is argued to be a result of Darwin's teleological explanations not conforming to either of the dominant philosophical justifications of teleology at that time. Darwin's explanatory practices conform well, however, to recent defenses of the teleological character of selection explanations.I would like to thank John Beatty, David Hull and one of this journal's readers for constructive comments on an earlier draft of this paper.     

Darwin's use of the analogy between artificial and natural selection

Conclusion The central role played by Darwin's analogy between selection under domestication and that under nature has been adequately appreciated, but I have indicated how important the domesticated organisms also were to other elements of Darwin's theory of evolution-his recognition of the constant principle of change, for instance, of the imperfection of adaptation, and of the extent of variation in nature. The further development of his theory and its presentation to the public likewise hinged on frequent reference to domesticates.We have seen that Darwin's reliance on the analogy between domesticated varieties and wild species was a bold and original step, in light of contemporary views on the nature of domesticates. However, as Darwin undoubtedly foresaw, his reliance on the analogy created difficulties as well as solving problems, and these began with his Malthusian codiscoverer of the principle of natural selection, Alfred Russel Wallace. Wallace's paper On the Tendency of Varieties to Depart Indefinitely from the Original Type, presented to the Linnean Scoiety along with the first public unveiling of Darwin's theory, states: We see, then, that no inferences as to varieties in a state of nature can be deduced from the observation of those occurring among domestic animals. The two are so much opposed to each other in every circumstance of their existence, that what applies to the one is almost sure not to apply to the other. Domestic animals are abnormal, irregular, artificial; they are subject to varieties which never occur and never can occur in a state of nature.⁶² Much has been made of the similarity of views of Darwin and Wallace, but this quotation surely reveals how utterly different their views were on what to Darwin was an important matter. Several critics of the Origin saw Darwin's reliance on the domesticates as his Achilles heel. As Young has pointed out, Samuel Wilberforce included the following passage in his attack on the Origin: Nor must we pass over unnoticed the transference of the argument from the domesticated to the untamed animals. Assuming that man as the selector can do much in a limited time, Mr. Darwin argues that Nature, a more powerful, a more continuous power, working over vastly extended ranges of time, can do more. But why should Nature, so uniform and persistent in all her operations, tend in this instance to change? Why should she become a selector of varieties?⁶³ Another critic, Fleeming Jenkin, found the analogy a weakness in Darwin's theory because of the limited extent of variation in any one direction in domestic animals and plants.⁶⁴ We have already seen that Darwin had confided a similar view to his notebook thirty years earlier, but changed his mind as a result of his profound study of domesticates. De Beer's reference to an English country gentleman's knowledge of domestic plants and animals and their breeding⁶⁵ fails totally to recognize the originality and depth of Darwin's knowledge of domesticates.Why did Darwin, against the currents of his time, rely so heavily on mankind's experience with domesticated organisms to shape his theory about species in nature? On reason is that only with domesticates was an approach that came close to experimental verification possible. Darwin fully realized the inadequacies of the experiment, as is emphasized by his repeated contrasting of selection under nature and selection by man. Yet the extensive experience and data of plant and animal breeders offered the only reliable base against which Darwin could continually challenge his views. As he wrote in the introduction to Variation, with domestication, man ... may be said to have been trying an experiment on a gigantic scale.⁶⁶ Given Darwin's high opinion of the quantitative work of Malthus and Quetelet (as emphasized by Schweber),⁶⁷ and his unremitting efforts to secure data by which to test his theories, it was inevitable that he should attach high significance to domesticated varieties. John Tyndall, in his Belfast address of 1874, said: The strength of the doctrine of Evolution consists, not in experimental demonstration (for the subject is hardly accessible to this mode of proof), but in its general harmony with scientific thought.⁶⁸ Darwin would have agreed with the latter thought, but I think he would have challenged the preceding one on the grounds that long experience with domesticated varieties did provide an element of experimental demonstration. It gave him confidence in his theory, and he used his vast knowledge of artificial selection boldly and creatively.     

Darwin and the Galápagos

Charles Darwin's historic visit to the Galápagos Islands in 1835 represents a landmark in the annals of science. But contrary to the legend long surrounding Darwin's famous Galápagos visit, he continued to believe that species were immutable for nearly a year and a half after leaving these islands. This delay in Darwin's evolutionary appreciation of the Galápagos evidence is largely owing to numerous misconceptions that he entertained about the islands, and their unique organic inhabitants, during the Beagle voyage. For example, Darwin mistakenly thought that the Galápagos tortoise–adult specimens of which he did not collect for scientific purposes–was not native to these islands. Hence he apparently interpreted reports of island-to-island differences among the tortoises as analogous to changes that are commonly undergone by species removed from their natural habitats. As for Darwin's finches, Darwin initially failed to recognize the closely related nature of the group, mistaking certain species for the forms that they appear, through adaptive radiation, to mimic. Moreover, what locality information he later published for his Galápagos finch specimens was derived almost entirely from the collections of three other Beagle shipmates, following his return to England. Even after he became an evolutionist, in March of 1837 (when he discussed his Galápagos birds with the eminent ornithologist John Gould), Darwin's theoretical understanding of evolution in the Galápagos continued to undergo significant developments for almost as many years as it took him to publish the Origin of Species (1859). The Darwin-Galápagos legend, with its romantic portrait of Darwin's 'eureka-like' insight into the Galápagos as a microcosmic 'laboratory of evolution', masks the complex nature of scientific discovery, and, thereby, the real nature of Darwin's genius.     

Darwin and the linguists: the coevolution of mind and language, part 2. The language-thought relationship

This paper examines Charles Darwin's idea that language-use and humanity's unique cognitive abilities reinforced each other's evolutionary emergence-an idea Darwin sketched in his early notebooks, set forth in his Descent of man (1871), and qualified in Descent's second (1874) edition. Darwin understood this coevolution process in essentially Lockean terms, based on John Locke's hints about the way language shapes thinking itself. Ironically, the linguist Friedrich Max Müller attacked Darwin's human descent theory by invoking a similar thesis, the German romantic notion of an identity between language and thought. Although Darwin avoided outright contradiction, when he came to defend himself against Müller's attacks, he undercut some of his own argumentation in favor of the coevolution idea. That is, he found it difficult to counter Müller's argument while also making a case for coevolution. Darwin's efforts in this area were further complicated by British and American writers who held a naturalistic view of speech origins yet still taught that language had been invented by fully evolved homo sapiens, thus denying coevolution.     

A new look at variation in Darwin's species of acorn barnacles

Darwin's studies on barnacles, begun to satisfy his curiosity about specimens from the Beagle , but later extended to the large collections of other naturalists, lasted for 8 years and produced a set of definitive monographs. Darwin was particularly troubled over the taxonomy of two groups of acorn barnacles, Balanus tintinnabulum and B. amphitrite , which he ultimately classified as clusters of wellmarked varieties. Recent studies, based on established taxonomic methods or on statistical treatment of morphometric data, suggest these are clusters of full species and that the 'intermediate' forms are just phenotypic variants. Darwin was also troubled by the small chthamalid intertidal barnacles, which he eventually grouped as varieties of a world-wide species, Chthamalus stellatur. Gel electrophoresis and morphometrics now show this to be a heterogenous assemblage of distinct species, some very different, others closer together, all with restricted geographical range, but all showing extreme variability in the characters normally used for classification.
Darwin's difficulties with the classification of the highly varying barnacles, and his anatomical studies on these peculiar animals, must have had considerable influence on the development of his theories about natural selection, more than is usually acknowledged by writers on evolution. These 'lost years' were in fact a period of intense zoological enquiry, and Darwin's change in attitude with regard to species and variation in nature underwent a big change, as can be seen from the letters and from the differences between the early drafts written before the barnacle work and the later Natural Selection and The Origin. Whether we regard the difficult groups of Balanus as clusters of species or clusters of varieties, they still draw attention to evolutionary processes as in Darwin's day.     

Darwin's artificial selection analogy and the generic character of "phyletic" evolution

This paper examines the way Charles Darwin applied his domestic breeding analogy to the practical workings of species evolution: that application, it is argued, centered on Darwin's distinction between methodical and unconscious selection. Methodical selection, which entailed pairing particular individuals for mating purposes, represented conditions of strict geographic isolation, obviously useful for species multiplication (speciation). By contrast, unconscious selection represented an open landmass with a large breeding population. Yet Darwin held that this latter scenario, which often would include multiple ecological subdistricts and thus partial isolation, was better suited for speciation than were isolated conditions. At the same time, many passages in Darwin's writings that apparently portrayedphyletic evolution exclusively (these including references to unconscious selection), actually applied to speciation as well, for phyletic change in a single district could constitute a local manifestation of a larger common-descent pattern. This generic use of "phyletic" change was reflected in Darwin's deployment of the unconscious selection analogy in his published writings as well as in his dispute with Moritz Wagner over the necessity of geographic isolation for speciation. We can thus understand Darwin's otherwise puzzling declaration in The Origin of Species that unconscious selection was 'more important' than the methodical approach.     

Was Darwin a creationist?

Throughout the Origin of Species, Darwin contrasts his theory of natural selection with the theory that God independently created each species. This makes it seem as though the Origin offers a scientific alternative to a theological worldview. A few months after the Origin appeared, however, the eminent anatomist Richard Owen published a review that pointed out the theological assumptions of Darwin's theory. Owen worked in the tradition of rational morphology, within which one might suggest that evolution occurs by processes that are continuous with those by which life arises from matter; in contrast, Darwin rested his account of life's origins on the notion that God created one or a few life forms upon which natural selection could act. Owen argued that Darwin's reliance on God to explain the origins of life makes his version of evolution no less supernatural than the special creationist that Darwin criticizes: although Darwin limits God to one or a few acts of creation, he still relies upon God to explain life's existence.     

Darwin's artificial selection as an experiment

Darwin used artificial selection (ASN) extensively and variedly in his theorizing. Darwin used ASN as an analogy to natural selection; he compared artificial to natural varieties, hereditary variation in nature to that in the breeding farm; and he also compared the overall effectiveness of the two processes. Most historians and philosophers of biology have argued that ASN worked as an analogical field in Darwin's theorizing. I will argue rather that this provides a limited and somewhat muddled view of Darwinian science. I say "limited" because I will show that Darwin also used ASN as a complex experimental field. And I say "muddled" because, if we concentrate on the analogical role exclusively, we conceive Darwinian science as rather disconnected from contemporary conceptions of "good science". I will argue that ASN should be conceived as a multifaceted experiment. As a traditional experiment, ASN established the efficacy of Darwin's preferred cause: natural selection. As a non-traditional experiment, ASN disclosed the nature of a crucial element in Darwin's evolutionary mechanics: the nature of hereditary variation. Finally, I will argue that the experiment conception should help us make sense of Darwin's comments regarding the "monstrous" nature of domestic breeds traditionally considered to be problematic.     

Darwin's explanation of races by means of sexual selection

In Darwin's Sacred Cause, Adrian Desmond and James Moore contend that "Darwin would put his utmost into sexual selection because the subject intrigued him, no doubt, but also for a deeper reason: the theory vindicated his lifelong commitment to human brotherhood" (2009: p. 360). Without questioning Desmond and Moore's evidence, I will raise some puzzles for their view. I will show that attention to the structure of Darwin's arguments in the Descent of Man shows that they are far from straightforward. As Desmond and Moore note, Darwin seems to have intended sexual selection in non-human animals to serve as evidence for sexual selection in humans. However, Darwin's account of sexual selection in humans was different from the canonical cases that Darwin described at great length. If explaining the origin of human races was the main reason for introducing sexual selection, and if sexual selection was a key piece of Darwin's anti-slavery arguments, then it is puzzling why Darwin would have spent so much time discussing cases that did not really support his argument for the origin of human races, and it is also puzzling that his argument for the origin of human races would be so (atypically) poor.     

Charles Darwin 1809-2009

The year 2009 is the bicentenary of the birth of Charles Darwin and the 150th anniversary of the publication of On the Origin of Species. This article briefly surveys his life and work, dispelling some common myths and summarizes Darwin's achievement and legacy at his death in 1882.     

Nietzsche's aesthetic critique of Darwin

Despite his position as one of the first philosophers to write in the "post-Darwinian" world, the critique of Darwin by Friedrich Nietzsche is often ignored for a host of unsatisfactory reasons. I argue that Nietzsche's critique of Darwin is important to the study of both Nietzsche's and Darwin's impact on philosophy. Further, I show that the central claims of Nietzsche's critique have been broadly misunderstood. I then present a new reading of Nietzsche's core criticism of Darwin. An important part of Nietzsche's response can best be understood as an aesthetic critique of Darwin, reacting to what he saw as Darwin having drained life of an essential component of objective aesthetic value. For Nietzsche, Darwin's theory is false because it is too intellectual, because it searches for rules, regulations, and uniformity in a realm where none of these are to be found - and, moreover, where they should not be found. Such a reading goes furthest toward making Nietzsche's criticism substantive and relevant. Finally, I attempt to relate this novel explanation of Nietzsche's critique to topics in contemporary philosophy of biology, particularly work on the evolutionary explanation of culture.     

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.     

Darwin's species category realism

Ever since Charles Darwin's On the Origin of Species was published, the received view has been that Darwin literally thought of species as not extra-mentally real. In 1969 Michael Ghiselin upset the received view by interpreting Darwin to mean that species taxa are indeed real but not the species category. In 1985 John Beatty took Ghiselin's thesis a step further by providing a strategy theory to explain why Darwin would say one thing (his repeated nominalistic definition of species) and do another (hold that species taxa are real). In the present paper I attempt to take this line of interpretation to a new level. Guided by the principle of charity, I provide and analyze a considerable amount of evidence from Darwin's mature writings (both private and published) to show that (contra Ghiselin and Beatty) Darwin did not simply accept the species delimitations of his fellow naturalists but actually employed, repeatedly and consistently, a species concept in a thoroughly modern sense, albeit with an implicit definition, a concept uniquely his own and fully in accord with his theory of evolution by natural selection. This implicit concept and definition is carefully reconstructed in the present paper. A new strategy theory is then provided to account for why Darwin would define species (both taxa and category) nominalistically on the one hand but delimit species realistically on the other.     

Darwin's evolutionary philosophy: The laws of change

The philosophical or metaphysical architecture of Darwin's theory of evolution by natural selection is analyzed and diflussed. It is argued that natural selection was for Darwin a paradigmatic case of a natural law of change — an exemplar of what Ghiselin (1969) has called selective retention laws. These selective retention laws lie at the basis of Darwin's revolutionary world view. In this essay special attention is paid to the consequences for Darwin's concept of species of his selective retention laws. Although Darwin himself explicity supported a variety of nominalism, implicit in the theory of natural selection is a solution to the dispute between nominalism and realism. It is argued that, although implicit, this view plays a very important role in Darwin's theory of natural selection as the means for the origin of species. It is in the context of these selective retention laws and their philosophical implications that Darwin's method is appraised in the light of recent criticisms, and the conclusion drawn that he successfully treated some philosophical problems by approaching them through natural history. Following this an outline of natural selection theory is presented in which all these philosophical issues are highlighted.