Over the decades, there has been substantial empirical evidence showing that the unity of species cannot be maintained by gene flow. The biological species concept is inconclusive on this point. The suggestion is made that the unity of species is maintained rather by selection constantly spreading new alleles throughout the species, or bygene circulation. There is a lack in conceptual distinction between gene flow and gene circulation which lies at the heart of the problem. The concept of gene circulation also (...) sheds some new light on the problem of typology and on such a broad concept as evolution. A new species definition is proposed. (shrink)

The purpose of this paper is to test the contemporary concept of biological species against some of the problems caused by treating species as spatiotemporally extended entities governed by criteria of persistence, identity, etc. After outlining the general problem of symmetric division in natural objects, I set out some useful distinctions (section 1) and confirm that species are not natural kinds (section 2). Section 3 takes up the separate issue of species definition, focusing on the Biological Species Concept (BSC). Sections (...) 4 and 5 examine the matter of species identity over space and time respectively, as determined by the BSC. Both gradualistic and punctuated equilibrium models of speciation are discussed. In section 6 I argue that the BSC fails to determine adequate criteria for dealing with certain kinds of speciation. Section 7 moves speculatively beyond the BSC to a brief examination of alternatives. (shrink)

Biological species have been treated traditionally as spatiotemporally unrestricted classes. If they are to perform the function which they do in the evolutionary process, they must be spatiotemporally localized individuals, historical entities. Reinterpreting biological species as historical entities solves several important anomalies in biology, in philosophy of biology, and within philosophy itself. It also has important implications for any attempt to present an "evolutionary" analysis of science and for sciences such as anthropology which are devoted to the study of single (...) species. (shrink)

Although it is possible to regard a species as a set with a special internal structure, it is preferable to regard a species as an individual precisely to emphasize this internal structure. It is necessary to recognize, moreover, that two organisms that are part of a single entity with respect to one process need not be part of a single entity with respect to another process. Furthermore, choosing to regard two entities (with respect to one process) as conspecific is not (...) to deny that there are two entities within this species. Thus, the systematist need not propose formal names for every entity he discovers, but the names he proposes ought to be as faithful to the relationship among the entities as is possible. (shrink)

We analyse theories and research approaches in ecology and find that they fall into two internally homogeneous groups of linked ideas, each comprising a unique set of premises. The two sets of interpretive statements are thus mutually exclusive; they constitute alternative theoretical developments in ecology and should not be seen as complementary. They can, therefore, be considered two paradigms (Kuhn, 1962). Our interpretation is supported by the minimal overlap, if any, in the premises and research directions of the two approaches. (...) We label the dominant group of ideas the demographic paradigm and the less developed one the autecological paradigm. The internal logic of the demographic paradigm of ecology is strongly developed and consistent. Its premises and logic extend into current models of population genetics, biogeography, palaeontology, evolutionary theory and conservation biology. Nevertheless, many phenomena contradict the premises of the demographic paradigm; these contradictions cannot be accommodated within its theoretical framework without major disruptions in logic ensuing. Such phenomena can, in contrast, be understood in terms of the autecological paradigm. Because the status and strengths of the autecological paradigm are generally unrecognised and because autecology is frequently misrepresented in the literature, we redefine its premises and clarify its structure and aims as an aid to its future development. (shrink)

Several species concepts are generally discussed and evaluated. Then the new definition, the pheno-genetic species concept, is developed; it reads: a species is the largest possible, regional evolutionary unit of pheno-genetically equal (in the typical, specific characters), identically reproducing demes. It is separated from sympatric species by a reproductive isolation that guarantees a unique evolution, an evolution different from that of other species and sufficiently uninfluenced, and that is accompanied by another distinctive pheno-genetic gap. It is separated from allopatric species (...) by a distinctive pheno-genetic gap that - in the case of missing reproductive isolation in bisexual forms — allows the conclusion that such an isolation would have developed, if the species had been sympatric with the allopatric species. This definition is applied to several situations of evolution. The effects of the concepts on the classification of lizards are demonstrated by examples. (shrink)

The longstanding species problem in biology has a history that suggests a solution, and that history is not the received history found in many texts written by biologists or philosophers. The notion of species as the division into subordinate groups of any generic predicate was the staple of logic from Aristotle through the middle ages until quite recently. However, the biological species concept during the same period was at first subtly and then overtly different. Unlike the logic sense, which relied (...) on definitions of the essence of both genus and species, biological species from the time of Epicurus were consistently considered to involve a reproductive element: in short, living species relied not on essential definitions, but on the generative cause, which might not be definable. I term this the generative conception of species: species were the generation by reproduction of form. This undercuts the claim that species before Darwin were essentialist, and divorces the notion of a type from that of essence. In fact, as late as the end of the nineteenth century, logicians explicitly treated biological “species” as a homonym only of logical essentialist species, and permitted considerable deviation from the type or form. At every point, species in logic were thought to be a subset, in effect, of some more general notion. I sketch a history of both philosophical and biological traditions of the species concept, before turning to the current conceptions. These are reconsidered in the light of this history, and in particular Mayr’s changing views are shown to be somewhat Whiggish, historiographically. Of the many touted biological species concepts, only one of which (Mayr’s) is called _the_ Biological Species Concept, none appears to capture all the relevant facts, intuitions, and operational requirements of biology. Cladistic conceptions, however, have much in common with the older philosophical literature, in that the natural group of cladism is the clade, or monophyletic group. After considering the Individuality Thesis, and the metaphysics of species, we see that species are the most particular terminal taxa in a clade, and that they are “defined” in terms of the particular synapomorphies, or evolved characters, that are causally responsible for keeping the lineages that organisms form distinct from one another. In this way, we can remain within the generative conception of species that has been in play for over two millennia, and yet avoid the pitfalls of prior attempts to find a universal conception of species. (shrink)

Alexander Moritzi is one of the most obscure figures in the early history of evolutionary thought. Best known for authoring a flora of Switzerland, Moritzi also published Réflexions sur l’espèce en histoire naturelle, a remarkable book about evolution with an overtly materialist viewpoint. In this work, Moritzi argues that the generally accepted line between species and varieties is artificial, that varieties can over time give rise to new species, and that deep time and turnover of species in the fossil record (...) clearly support an evolutionary interpretation of biological diversity. Moritzi was also a gradualist and viewed relationships between taxa as best represented by a ramifying tree. Although Réflexions was the first full book to be written on the topic of evolution following Lamarck’s Philosophie zoologique, Moritzi’s evolutionist contribution was stillborn, read by almost no one in his lifetime and ultimately absent from the many historiographies of evolutionary thought. This is unfortunate since many of the arguments Moritzi marshaled on behalf of an evolutionary explanation of life can be found in subsequent transmutationist writings by Frédéric Gérard, Robert Chambers, Henri Lecoq, Baden Powell, Charles Naudin, Herbert Spencer, Alfred Russel Wallace, and Charles Darwin—none of whom is likely to have ever known of the existence of Réflexions. Finally, Moritzi’s arguments, along with those found in Darwin’s private essay on evolution of the same year, provide an excellent window into the state of evolutionary thought and debate over the nature of species at the beginning of the 1840s. (shrink)

Species are central to biology, but there is currently no agreement on what the adequate species concept should be, and many have adopted a pluralist stance: different species concepts will be required for different purposes. This thesis is a multidimensional analysis of species pluralism. First I explicate how pluralism differs monism and relativism. I then consider the history of species pluralism. I argue that we must re-frame the species problem, and that re-evaluating Aristotle's role in the histories of systematics can (...) shed light on pluralism. Next I consider different forms of pluralism: evolutionary and extra-evolutionary species pluralism, which differ in their stance on evolutionary theory. I show that pluralism is more than a debate about the species category, but a debate about which concepts are legitimate and a claim about how they interact with one another. Following that, I consider what sort of ontology is required for different forms of species pluralism. I argue that pluralists who deny the unity of biology will require a further plurality of frameworks, while those that ground their pluralism in evolution need only one framework. Finally, I consider what pluralism means for biological practice. I argue that species concepts are tools, and reflect on how pluralism can illuminate the way systematists approach the discovery of new species of yeast. Pluralism can make sense of the way species concepts are used, and can be developed to aid researchers in thinking about how to use the right tools for the right jobs. (shrink)

Ethnobiology has a long tradition of metaphysical debates about the “naturalness,” “objectivity”, “reality”, and “universality” of classifications. Especially the work of Brent Berlin has been influential in developing a “convergence metaphysics” that explains cross-cultural similarities of knowledge systems through shared recognition of objective discontinuities in nature. Despite its influence on the development of the field, convergence metaphysics has largely fallen out of favor as contemporary ethnobiologists tend to emphasize the locality and diversity of classificatory practices. The aim of this article (...) is twofold: First, I provide a historical account of the rise and fall of convergence metaphysics in ethnobiology. I show how convergence metaphysics emerged as an innovative theoretical program in the wake of the “cognitive revolution” and the “modern evolutionary synthesis” but failed to incorporate both theoretical insights and political concerns that gained prominence in the 1980s and 1990s. Second, I develop a positive proposal of how to engage with metaphysical issues in ethnobiology. By integrating traditional research on convergence of classifications with more nuanced accounts of distinctly local categories, a revamped metaphysics of ethnobiological classification can make substantial contributions to debates about ontological difference in anthropology and about the relation between applied and theoretical ethnobiology. (shrink)

The dichotomy between ‘typological thinking’ and ‘population thinking’ features in a range of debates in contemporary and historical biology. The origins of this dichotomy are often traced to Ernst Mayr, who is said to have coined it in the 1950s as a rhetorical device that could be used to shield the Modern Synthesis from attacks by the opponents of population biology. In this two-part essay I argue that the origins of the typology/population dichotomy are considerably more complicated and more interesting (...) than is commonly thought. In this first part, I will argue that Mayr's dichotomy was based on two distinct type/population contrasts that had been articulated much earlier by George Gaylord Simpson and Theodosius Dobzhansky. Their distinctions made eminent sense in their own, isolated contexts. In the second part, I will show how Mayr conflated these type/population distinctions and blended in some of his own, unrelated concerns with ‘types’ of a rather different sort. Although Mayr told his early critics that he was merely making “a temporary oversimplification,” he ended up burdening the history and philosophy of biology with a troubled dichotomy. (shrink)

For more than fifty years, taxonomists have proposed numerous alternative definitions of species while they searched for a unique, comprehensive, and persuasive definition. This monograph shows that these efforts have been unnecessary, and indeed have provably been a pursuit of a will o’ the wisp because they have failed to recognize the theoretical impossibility of what they seek to accomplish. A clear and rigorous understanding of the logic underlying species definition leads both to a recognition of the inescapable ambiguity that (...) affects the definition of species, and to a framework-relative approach to species definition that is logically compelling, i.e., cannot not be accepted without inconsistency. An appendix reflects upon the conclusions reached, applying them in an intellectually whimsical taxonomic thought experiment that conjectures the possibility of an emerging new human species. (shrink)

Numerous concepts exist for biological species. This diversity of ideas derives from a number of sources ranging from investigative study of particular taxa and character sets to philosophical aptitude and world view to operationalism and nomenclatorial rules. While usually viewed as counterproductive, in reality these varied concepts can greatly enhance our efforts to discover and understand biological diversity. Moreover, this continued "turf war" and dilemma over species can be resolved if the various concepts are viewed in a hierarchical system and (...) each evaluated for its inherent level of consilience. Under this paradigm a theoretically appropriate, highly consilient concept of species capable of colligating the abundant types of species diversity offers the best guidance for developing and employing secondary operational concepts for identifying diversity. Of all the concepts currently recognized, only the non-operational Evolutionary Species Concept corresponds to the requisite parameters and, therefore, should serve as the theoretical concept appropriate for the category Species. As operational concepts, the remaining ideas have been incompatible with one another in their ability to encompass species diversity because each has restrictive criteria as to what qualifies as a species. However, the operational concepts can complement one another and do serve a vital role under the Evolutionary Species Concept as fundamental tools necessary for discovering diversity compatible with the primary theoretical concept. Thus, the proposed hierarchical system of primary and secondary concepts promises both the most productive framework for mutual respect for varied concepts and the most efficient and effective means for revealing species diversity. (shrink)

At least 22 concepts of species are in use today and many of these are notably incompatible in their accounts of biological diversity. Much of the traditional turmoil embodied in the species problem ultimately derives from the packaging of inappropriate criteria for species into a single concept. This results from a traditional conflation of function of concepts with their applications, definitions with concepts, taxonomic categories with groups, and the ontological status of real species with teleological approaches to recover them. Analogous (...) to classifications of supraspecific taxa, our forging inappropriate and ambiguous information relating to theoretical and operational discussions of species ultimately results in a trade-off between convenience, accuracy, precision, and the successful recovery of natural biological diversity. Hence, none of these expectations or intentions of species or classifications is attainable through composite, and possibly discordant, concepts of biological diversity or its descent. Reviewing and evaluating the concepts of species for their theoretical and operational qualities illustrates that a monistic, primary concept of species, applicable to the various entities believed to be species, is essential. This evaluation reveals only one theoretical concept as appropriate for species, the Evolutionary Species Concept. This conceptualization functions as a primary concept and is essential in structuring our ideas and perceptions of real species in the natural world. The remaining concepts are secondary, forming a hierarchy of definitional guidelines subordinate to the primary concept, and are essential to the study of species in practice. Secondary concepts should be used as operational tools, where appropriate, across the variance in natural diversity to discover entities in accord with the primary concept. Without this theoretical and empirical structuring of concepts of species our mission to achieve reconciliation and understanding of pattern and process of the natural world will fail. (shrink)

The biological species concept deals both with the meaning of the sexual species as a harmonious gene pool and with its protection against deleterious outbreeding (effected by isolating mechanisms). According to the Darwin-Muller-Mayr theory isolating mechanisms are acquired by incipient species during alloparty. Isolating mechanisms are not the result of ad hoc selection, but of a change of function of properties acquired during the preceding isolation of the incipient species. The role of behavioral properties (recognition) among the isolating mechanisms has (...) long been recognized and described by naturalists but was rejected as basis of a species definition for a number of valid reasons. (shrink)

Following Mayr (1961) evolutionary biologists often maintain that the hallmark of biology is its evolutionary perspective. In this view, biologists distinguish themselves from other natural scientists by their emphasis on why-questions. Why-questions are legitimate in biology but not in other natural sciences because of the selective character of the process by means of which living objects acquire their characteristics. For that reason, why-questions should be answered in terms of natural selection. Functional biology is seen as a reductionist science that applies (...) physics and chemistry to answer how-questions but lacks a biological point of view of its own. In this paper I dispute this image of functional biology. A close look at the kinds of issues studied in biology and at the way in which these issues are studied shows that functional biology employs a distinctive biological perspective that is not rooted in selection. This functional perspective is characterized by its concern with the requirements of the life-state and the way in which these are met. (shrink)

The essentialism story is a version of the history of biological classification that was fabricated between 1953 and 1968 by Ernst Mayr, who combined contributions from Arthur Cain and David Hull with his own grudge against Plato. It portrays pre-Darwinian taxonomists as caught in the grip of an ancient philosophy called essentialism, from which they were not released until Charles Darwin's 1859 Origin of Species. Mayr's motive was to promote the Modern Synthesis in opposition to the typology of idealist morphologists; (...) demonizing Plato served this end. Arthur Cain's picture of Linnaeus as a follower of 'Aristotelian' (scholastic) logic was woven into the story, along with David Hull's application of Karl Popper's term, 'essentialism', which Mayr accepted in 1968 as a synonym for what he had called 'typological thinking'. Although Mayr also pointed out the importance of empiricism in the history of taxonomy, the essentialism story still dominates the secondary literature. The history of the first telling of the essentialism story exposes its scant basis in fact. (shrink)

Weismann's ideas on species transmutation were first expressed in his famous debate with Moritz Wagner on the mechanism of speciation. Wagner suggested that the isolation of a colony from its original source is a preliminary and necessary factor for speciation. Weismann accepted a secondary, facilitating role for isolation, but argued that natural and sexual selection are the primary driving forces of species transmutation, and are always necessary and often sufficient causes for its occurrence. The debate with Wagner, which occurred between (...) 1868 and 1872 within the framework of Darwin's discussions of geographical distribution, was Weismann's first public battle over the mechanism of evolution. This paper, which offers the first comprehensive analysis of this debate, extends previous analyses and throws light on the underlying beliefs and motivations of these early evolutionists, focusing mainly on Weismann's views and showing his commitment to what he later called "the all sufficiency of Natural Selection." It led to the crystallization of his ideas on the central and essential role of selection, both natural and sexual, in all processes of evolution, and, already at this early stage in his theoretical thinking, was coupled with sophisticated and nuanced approach to biological organization. The paper also discusses Ernst Mayr's analysis of the debate and highlights aspects of Weismann's views that were overlooked by Mayr and were peripheral to the discussions of other historians of biology. (shrink)

This paper is based on my M.Sc. dissertation: ‘The Origins of Numerical Taxonomy’ 1985, submitted to the University of Leicester during the tenure of a D.E.S. State Studentship. For this work I drew extensively on interviews with Professors A. J. Cain, G. A. Harrison, R. R. Sokal and P. H. A. Sneath. I am very grateful to them for their time, interest and encouragement. Without the indefatigable assistance of Jon Harwood, this paper would never have been finished.

This paper uses two case studies to explore an interest-relative view of taxonomy and how it complements kind pluralism in biology. First, I consider the ABC island bear, which can be correctly classified into more than one species. I argue that this classificatory pluralism can be explained by reference to the range of alternative explanatory interests in biology. In the second half of the paper, I pursue an interest-relative view of classification more generally. I then apply the resultant view to (...) a second case study: whether whales are fish. I argue that this question is not one about scientific vs folk usage, as has been assumed. I also develop a new view: that Fish should be rejected as a category, both from the point of view of biological science, and from the point of view of folk taxonomy. Along the way, I use the interest-relative view to shed light on the circumstances under which higher taxa should be accepted as legitimate categories for biological science. (shrink)

This article examines the critique of the biological species concept advanced by protozoan geneticist Tracy Sonneborn at the 1955 AAAS symposium on "the species problem," published subsequently in 1957. Although Sonneborn was a strong proponent of a population genetical conception of species, he became critical of the biological species concept for its failure to incorporate asexual and obligatory inbreeding organisms. It is argued that Sonneborn's intimate knowledge of the ciliate protozoan Paramecium aurelia species complex brought him into conflict with a (...) growing pressure in the biological sciences to emphasize universal principles of life. Faced with the need to defend the value of P. aurelia as an investigative tool, Sonneborn argued that the sharp break in nature between sexual and asexual organisms posited by proponents of the biological species concept was not an existential feature of the living world, but rather the misleading consequence of an operational definition of species based only upon sexual organisms. Drawing upon his knowledge of the immense variability of P. aurelia, he proposed instead a continuum of breeding systems from obligatory outbreeding to asexual organisms, and a more broadly unifying definition of species that incorporated asexual as well as sexual organisms. Paradoxically, the push for unification that then characterized the evolutionary synthesis served to debar critical consideration of Sonneborn's more unificatory alternative, and his underlying contention that biological anomaly could serve as an important source of conceptual unification. (shrink)

Ernst Mayr's typological/population distinction is a conceptual thread that runs throughout much of his work in systematics, evolutionary biology, and the history and philosophy of biology. Mayr himself claims that typological thinking originated in the philosophy of Plato and that population thinking was first introduced by Charles Darwin and field naturalists. A more proximate origin of the typological/population thinking, however, is found in Mayr's own work on species. This paper traces the antecedents of the typological/population distinction by detailing Mayr's changing (...) views of species between 1942 and 1955. During this period, Mayr struggles to refine the biological species concept in the face of tensions that exist between studying species locally and studying them as geographically distributed collections of variable populations. The typological/population distinction is first formulated in 1955, when Mayr generalizes from the type concept versus the population concept in taxonomy to typological versus population thinking in biology more generally. Mayr's appeal to the more general distinction between typological and population thinking coincides with the waning status of natural history and evolutionary biology that occurs in the early 1950s and the distinction plays an important role in Mayr's efforts to legitimate the natural historical sciences. (shrink)

There is a perennial philosophical dream of a certain natural order for the natural kinds. The name of this dream is ‘the hierarchy requirement’. According to this postulate, proper natural kinds form a taxonomy which is both unique and traditional. Here I demonstrate that complex scientific objects exist: objects which generate different systems of scientific classification, produce myriad legitimate alternatives amongst the nonetheless still natural kinds, and make the hierarchical dream impossible to realize, except at absurdly great cost. Philosophical hopes (...) for a certain order in nature cannot be fulfilled. Natural kinds crosscut one another, ubiquitously so, and this crosscutting spells the end of the hierarchical dream. (shrink)

The circumscription of taxa and classification of organisms are fundamental tasks in the systematization of biological diversity. Their success depends on a unified idea concerning the species concept, evolution, and taxonomy; paradoxically, however, it requires a complete distinction between taxa and evolutionary units. To justify this view, I discuss these three topics of systematics. Species concepts are examined, and I propose a redefinition for the Taxonomic Species Concept based on nomenclatural properties, in which species are classes conventionally represented by a (...) binomial. Speciation is subsequently discussed, to demonstrate that concepts on the evolutionary process are damaged when species are considered as evolutionary units. Speciation should be considered a transition among patterns of a population and, consequently, always a sympatric process. This view contrasts with the majority of speciation models, which analyze cladogeneses and classify speciation geographically, usually considering allopatry the essential condition for the differentiation process. Finally, taxonomy is considered, to show that the equivalence between evolutionary and taxonomic units may also damage the practice of biological systematization. Principles and rules of nomenclature and classification should offer freedom to accommodate divergent opinions about systematics and to incorporate the evolution of knowledge; therefore, they should remain independent of biological theories. (shrink)

This is an essay about ethics and environmental responsibility. The thesis is that biologic species qua species--not only as collections of individuals or as elements of ecosystems--deserve moral regard. The argument establishes moral considerability on powers and freedoms of relative self-determination and autonomy. It is argued that species are living beings in their own right with their own projects and interests which deserve special regard. The essay draws from the arguments of Plato, Aristotle, Plotinus, Boethius, Avicenna, Maimonides, Leibniz, Spinoza, Kant, (...) and others, concerning the moral value of natural beings, but situates itself in the contemporary dialogue of environmental ethics. Lengthy consideration is given to species concepts defended by evolution theorists, biological systematists, and ecologists. ;The argument claims that natural beings, including species, have moral value because they have projects and interests which make a legitimate, but not universal, claim on the moral agent. Beings make moral claims when they are integral and integrating, individual, and concreative--conditions comparable to those with which we describe the moral status of a person. We may call such beings rational by analogy to the integration and singularity of intellect, and confer upon them analogous moral consideration. They are due regard in proportion to their projects in the same sense that moral subjects are due regard for having the projects of moral subjects. (shrink)