Biologists and philosophers that debate the existence of the species category fall into two camps. Some believe that the species category does not exist and the term 'species' should be eliminated from biology. Others believe that with new biological insights or the application of philosophical ideas, we can be confident that the species category exists. This paper offers a different approach to the species problem. We should be skeptical of the species category, but not skeptical of the existence of those (...) taxa biologists call 'species.' And despite skepticism over the species category, there are pragmatic reasons for keeping the word 'species.' This approach to the species problem is not new. Darwin employed a similar strategy to the species problem 150 years ago. (shrink)

I construe the question Are species sets? as a question about whether species can be conceived of as sets, as the term set is understood by contemporary logicians. The question is distinct from the question Are species classes?: The conception of classes invoked by Hull and others differs from the logician's conception of a set. I argue that species can be conceived of as sets, insofar as one could identify a set with any given species and that identification would satisfy (...) three desiderata: the set would be a set of organisms, the identification would be apposite, and the identification would permit the formulation of statements about species in set-theoretic terms. One cannot, however, identify a species with any given set. Understanding the claim that species are sets in this way enables one to understand better the dispute between some who accept the claim (e.g., Kitcher 1984, 1987) and some who apparently reject it (e.g., Mayr 1987). (shrink)

The correct explanation of why species, in evolutionary theory, are individuals and not classes is the cladistic species concept. The cladistic species concept defines species as the group of organisms between two speciation events, or between one speciation event and one extinction event, or (for living species) that are descended from a speciation event. It is a theoretical concept, and therefore has the virtue of distinguishing clearly the theoretical nature of species from the practical criteria by which species may be (...) recognized at any one time. Ecological or biological (reproductive) criteria may help in the practical recognition of species. Ecological and biological species concepts are also needed to explain why cladistic species exist as distinct lineages, and to explain what exactly takes place during a speciation event. The ecological and biological species concepts work only as sub-theories of the cladistic species concept and if taken by themselves independently of cladism they are liable to blunder. The biological species concept neither provides a better explanation of species indivudualism than the ecological species concept, nor, taken by itself, can the biological species concept even be reconciled with species individualism. Taking the individuality of species seriously requires subordinating the biological, to the cladistic, species concept. (shrink)

Species serve as both the basic units of macroevolutionary studies and as the basic units of taxonomic classification. In this paper I argue that the taxa identified as species by the Phylogenetic Species Concept (Mishler and Brandon 1987) are the units of biological organization most causally relevant to the evolutionary process but that such units exist at multiple levels within the hierarchy of any phylogenetic lineage. The PSC gives us no way of identifying one of these levels as the privileged (...) level on which taxonomic classifications can be based. (shrink)

Philosophers of biology, along with everyone else, generally perceive life to fall into two broad categories, the microbes and macrobes, and then pay most of their attention to the latter. ‘Macrobe’ is the word we propose for larger life forms, and we use it as part of an argument for microbial equality. We suggest that taking more notice of microbes – the dominant life form on the planet, both now and throughout evolutionary history – will transform some of the philosophy (...) of biology’s standard ideas on ontology, evolution, taxonomy and biodiversity. We set out a number of recent developments in microbiology – including biofilm formation, chemotaxis, quorum sensing and gene transfer – that highlight microbial capacities for cooperation and communication and break down conventional thinking that microbes are solely or primarily single-celled organisms. These insights also bring new perspectives to the levels of selection debate, as well as to discussions of the evolution and nature of multicellularity, and to neo-Darwinian understandings of evolutionary mechanisms. We show how these revisions lead to further complications for microbial classification and the philosophies of systematics and biodiversity. Incorporating microbial insights into the philosophy of biology will challenge many of its assumptions, but also give greater scope and depth to its investigations. (shrink)

Philosophical discussions of biological classification have failed to recognise the central role of homology in the classification of biological parts and processes. One reason for this is a misunderstanding of the relationship between judgments of homology and the core explanatory theories of biology. The textbook characterisation of homology as identity by descent is commonly regarded as a definition. I suggest instead that it is one of several attempts to explain the phenomena of homology. Twenty years ago the ‘new experimentalist’ movement (...) in philosophy of science drew attention to the fact that many experimental phenomena have a ‘life of their own’: the conviction that they are real is not dependent on the theories used to characterise and explain them. I suggest that something similar can be true of descriptive phenomena, and that many homologies are phenomena of this kind. As a result the descriptive biology of form and function has a life of its own—a degree of epistemological independence from the theories that explain form and function. I also suggest that the two major ‘homology concepts’ in contemporary biology, usually seen as two competing definitions, are in reality complementary elements of the biological explanation of homology. (shrink)

I adopt a cladistic view of species, and explore the possibility that there exists an equally valuable cladistic view of organismic traits. This suggestion seems to run counter to the stress on functional views of biological traits in recent work in philosophy and psychology. I show how the tension between these two views can be defused with a multilevel view of biological explanation. Despite the attractions of this compromise, I conclude that we must reject it, and adopt an essentially cladistic (...) conception of biological traits. (shrink)

Darwinists classify biological traits either by their ancestry (homology) or by their adaptive role. Only the latter can provide traditional natural kinds, but only the former is practicable. Process structuralists exploit this embarrassment to argue for non-Darwinian classifications in terms of underlying developmental mechanisms. This new taxonomy will also explain phylogenetic inertia and developmental constraint. I argue that Darwinian homologies are natural kinds despite having historical essences and being spatio-temporally restricted. Furthermore, process structuralist explanations of biological form require an unwarranted (...) assumption about the space of developmental possibility. (shrink)

Species pluralism gives us reason to doubt the existence of the species category. The problem is not that species concepts are chosen according to our interests or that pluralism and the desire for hierarchical classifications are incompatible. The problem is that the various taxa we call 'species' lack a common unifying feature.

Most biologists use the Linnaean system for constructing classifications of the organic world. The Linnaean system, however, has lost its theoretical basis due to the shift in biology from creationist and essentialist tenets to evolutionary theory. As a result, the Linnaean system is both cumbersome and ontologically vacuous. This paper illustrates the problems facing the Linnaean system, and ends with a brief introduction to an alternative approach to biological classification.

There is no question that the constituents of cells and organisms are joined together by the part-whole relation. Genes are part of cells, and cells are part of organisms. Species taxa, however, have traditionally been conceived of, not as wholes with parts, but as classes with members. But why does the relation change abruptly from part-whole to class-membership above the level of organisms? Ghiselin, Hull and others have argued that it doesn't. Cells and organisms are cohesive mereological sums, and since (...) species taxa are like cells and organisms in the relevant respects, they, too, are cohesive mereological sums. I provide further reasons in support of the thesis that species are mereological sums. I argue, moreover, that the advocate of this thesis is committed to a form of pluralism with respect to the species concept. (shrink)

Recent and ongoing debates in biology and in the philosophy of biology reveal widespread dissatisfaction with the current definitions or circumscriptions, which are often vague or controversial, of key concepts such as the gene, individual, species, and homology, and even of whole disciplinary fields within the life sciences. To some extent, the long growing awareness of these conceptual issues and the contrasting views defended in their regard can be construed as a symptom of the need to revisit traditional unchallenged partitions (...) between the specialist disciplines within the life sciences. I argue here that the current relationships between anchor disciplines (e.g., developmental biology, evolutionary biology, biology of reproduction) and nomadic concepts wandering between them is worth being explored from a reciprocal perspective, by selecting suitable anchor concepts around which disciplinary fields can flexibly move. Three examples are offered, focusing on generalized anchor concepts of generation (redefined in a way that suggests new perspectives on development and reproduction), organizational module (with a wide-ranging domain of application in comparative morphology, developmental biology, and evolutionary biology) and species as unit of representation of biological diversity (suggesting a taxonomic pluralism that must be managed with suitable adjustments of current nomenclature rules). (shrink)

The relatively new field of evolutionary developmental biology continues to attract considerable attention from biologists, philosophers, and historians, in part, because work in this field demonstrates that important changes are underway within biology. Though studies of development and evolution were closely connected during the 19th century, continued work in genetics fostered a general split between the two during the first decades of the twentieth century (e.g., Allen 1978; Gilbert 1978; Mayr and Provine 1980; Gilbert, Opitz and..

Identifying the necessary and sufficient conditions for individuating and classifying diseases is a matter of great importance in the fields of law, ethics, epidemiology, and of course, medicine. In this paper, I first propose a means of achieving this goal, ensuring that no two distinct disease-types could correctly be ascribed to the same disease-token. I then posit a metaphysical ontology of diseases—that is, I give an account of what a disease is. This is essential to providing the most effective means (...) of interfering with disease processes. Following existing work in the philosophy of medicine and epidemiology (primarily Christopher Boorse; Caroline Whitbeck; Alexander Broadbent), philosophy of biology (Joseph LaPorte; D.L. Hull), conditional analyses of causation (J.L. Mackie; David Lewis), and recent literature on dispositional essentialism (Stephen Mumford and Rani Anjum; Alexander Bird), I endorse a dispositional conception of disease. Following discussion of various conceptions of disease-identity, their relations to the clinical and pathological effects of the diseases in question, and how diseases are treated, I conclude (i) that diseases should be individuated by their causes, and (ii) that diseases are causal processes best seen as simultaneously acting sequences of mutually manifesting dispositions. (shrink)

In addition to the distinction between species as a category and speciesas a taxon, the word species is ambiguous in a very different butequally important way, namely the temporal distinction between horizontal andvertical species. Although often found in the relevant literature, thisdistinction has thus far remained vague and undefined. In this paper the use ofthe distinction is explored, an attempt is made to clarify and define it, andthen the relation between the two dimensions and the implications of thatrelation are examined. (...) Using Darwin's analogy of language evolution forspeciesevolution, and by appealing to a major change in the conception of languagebetween 19th- and 20th-century linguistics, it is argued that the horizontaldimension has priority (pragmatic, epistemological, logical, and ontological)over the vertical dimension. This has immense ramifications for the modernspecies problem. Fundamentally, it favors horizontal species concepts oververtical ones. In so doing it places species realism on a much more securefoundation and largely undercuts species pluralism. In addition it raises aserious problem for the increasingly popular family of phylogenetic speciesconcepts, which generally suffer from a dimensionality confusion. However,thereis a recent trend within this family that attempts to restore the priority ofthe horizontal dimension. It is concluded that this trend should be affirmedandthat the species-as-individuals view should be abandoned. (shrink)

Gayon's recent claim that Buffon developed a concept of species as physical individuals is critically examined and rejected. Also critically examined and rejected is Gayon's more central thesis that as a consequence of his analysis of Buffon's species concept, and also of Darwin's species concept, it is clear that modern evolutionary theory does not require species to be physical individuals. While I agree with Gayon's conclusion that modern evolutionary theory does not require species to be physical individuals, I disagree with (...) his reasons and instead provide logical rather than historical reasons for the same conclusion. (shrink)

The concept of individuality as applied to species, an important advance in the philosophy of evolutionary biology, is nevertheless in need of refinement. Four important subparts of this concept must be recognized: spatial boundaries, temporal boundaries, integration, and cohesion. Not all species necessarily meet all of these. Two very different types of pluralism have been advocated with respect to species, only one of which is satisfactory. An often unrecognized distinction between grouping and ranking components of any species concept is necessary. (...) A phylogenetic species concept is advocated that uses a grouping criterion of monophyly in a cladistic sense, and a ranking criterion based on those causal processes that are most important in producing and maintaining lineages in a particular case. Such causal processes can include actual interbreeding, selective constraints, and developmental canalization. The widespread use of the biological species concept is flawed for two reasons: because of a failure to distinguish grouping from ranking criteria and because of an unwarranted emphasis on the importance of interbreeding as a universal causal factor controlling evolutionary diversification. The potential to interbreed is not in itself a process; it is instead a result of a diversity of processes which result in shared selective environments and common developmental programs. These types of processes act in both sexual and asexual organisms, thus the phylogenetic species concept can reflect an underlying unity that the biological species concept can not. (shrink)

I criticize conceptual pluralism, as endorsed recently by John Dupre and Philip Kitcher, for failing to supply strategies for demarcating science from non-science. Using creation-science as a test case, I argue that pluralism blocks arguments that keep creation-science in check and that metaphysical pluralism offers it positive, metaphysical support. Logical empiricism, however, still provides useful resources to reconfigure and manage the problem of creation-science in those practical and political contexts where pluralism will fail.

The continuing discussion of the species problem suffers from the lack of a coherent ontological theory as a basis for determining whether species have an ontological status. It has attempted to apply a full-fledged metaphysical theory to the species problem: the ontology of Mario Bunge. In doing so a few ontological fundamentals including system, individual, real and conceptual object, and law are briefly introduced. It is with the help of these fundamentals that an analysis of the species-as-individuals thesis is carried (...) out, concluding that species are not individuals (things), but natural kinds, and that they have no ontological status. In contradistinction to the traditional view of natural kinds involving possible worlds metaphysics and semantics a notion of natural kind is given in terms of the state space approach and of nomological equivalence. (shrink)

In this paper I take issue with the doctrine that organisms belong of their very essence to the natural kinds (or biological taxa, if these are not kinds) to which they belong. This view holds that any human essentially belongs to the species Homo sapiens, any feline essentially belongs to the cat family, and so on. I survey the various competing views in biological systematics. These offer different explanations for what it is that makes a member of one species, family, (...) etc. a member of that taxon. Unfortunately, none of them offers an explanation that is compatible with the essentialism in question. (shrink)

A number of philosophers and ‘evolutionary psychologists’ have argued that attacks on adaptationism in contemporary biology are misguided. These thinkers identify anti-adaptationism with advocacy of non-adaptive modes of explanation. They overlook the influence of anti-adaptationism in the development of more rigorous forms of adaptive explanation. Many biologists who reject adaptationism do not reject Darwinism. Instead, they have pioneered the contemporary historical turn in the study of adaptation. One real issue which remains unresolved amongst these methodological advances is the nature of (...) ‘phylogenetic inertia’. To what extent is an adaptive explanation needed for the persistence of a trait as well as its origin? (shrink)

Marc Ereshefsky argues that pluralism about species suggests that the species concept is not theoretically useful. It is to be abandoned in favor of several concrete species concepts that denote real categories. While accepting species pluralism, the present paper rejects eliminativism about the species category. It is argued that the species concept is important and that it is possible to make sense of a general species concept despite the existence of different concrete species concepts.

The continuing discussion of the species problem suffers from the lack of a coherent ontological theory as a basis for determining whether species have an ontological status. It has attempted to apply a full-fledged metaphysical theory to the species problem: the ontology of Mario Bunge. In doing so a few ontological fundamentals including system, individual, real and conceptual object, and law are briefly introduced. It is with the help of these fundamentals that an analysis of the species-as-individuals thesis is carried (...) out, concluding that species are not individuals (things), but natural kinds, and that they have no ontological status. In contradistinction to the traditional view of natural kinds involving possible worlds metaphysics and semantics a notion of natural kind is given in terms of the state space approach and of nomological equivalence. (shrink)

The view that species are individuals, as developed by Ghiselinand Hull, has been touted as explaining the role of type specimens intaxonomy. The kinship of this explanation with the Kripke-Putnam theoryof names has long been recognized. In light of this kinship, however,Hull's account of type specimens can be seen to entail two relatedinscrutability problems – unreasonable limits placed on the natureand extent of biological knowledge. An appreciation for these problemsinvites us to consider the proper relation between metaphysical andepistemological inquires in (...) the philosophy of science. (shrink)

The Empiricist or Lockean view says natural kinds do not exist objectively in nature but are practical categories reflecting use of words. The Modern, Ostensive view says they do exist, and one can refer to such a kind by ostention and recursion, assuming his designation of it is related causally to the kind itself. However, this leads to a problem: Kinds are abstract repeatables, and it seems impossible that abstractions could have causal force. In defence of the Modern view, I (...) suggest we can think of kinds as — or as like — ecological niches existing in nature, which are causally effective by virtue of the fact that they predictively determine (some) properties of the things that happen to occupy them. (shrink)

Elliott Sober''s selection for/selection of distinction has been widely used to clarify the idea that some properties of organisms are side-effects of selection processes. It has also been used, however, to choose between different descriptions of an evolutionary product when assigning biological functions to that product. We suggest that there is a characteristic error in these uses of the distinction. Complementary descriptions of function are misrepresented as mutually excluding one another. This error arises from a failure to appreciate that selection (...) processes can be described at several different theoretical levels. (shrink)

This paper takes up the cause of species pluralism. An argument for species pluralism is provided and standard monist objections to pluralism are answered. A new form of species pluralism is developed and shown to be an improvement over previous forms. This paper also offers a general foundation on which to base a pluralistic approach to biological classification.

The Narrow Evolutionary Psychology Movement represents itself as a major reorientation of the social/behavioral sciences, a group of sciences previously dominated by something called the ‘Standard Social Science Model’. Narrow Evolutionary Psychology alleges that the SSSM treated the mind, and particularly those aspects of the mind that exhibit cultural variation, as devoid of any marks of its evolutionary history. Adherents of Narrow Evolutionary Psychology often suggest that the SSSM owed more to ideology than to evidence. It was the child of (...) the 1960s, representing a politically motivated insistence on the possibility of changing social arrangements such as gender roles: " ‘Not so long ago jealousy was considered a pointless, archaic institution in need of reform. But like other denials of human nature from the 1960s, this bromide has not aged well.’ ) " This view of history does not ring true to those, like the authors, who have worked in traditions of evolutionary theorizing about the mind that have a continuous history through the 1960s and beyond: traditions such as evolutionary epistemology and psychoevolutionary research into emotion (Griffiths. (shrink)

The theory of concepts advanced in the dissertation aims at accounting for a) how a concept makes successful practice possible, and b) how a scientific concept can be subject to rational change in the course of history. Traditional accounts in the philosophy of science have usually studied concepts in terms only of their reference; their concern is to establish a stability of reference in order to address the incommensurability problem. My discussion, in contrast, suggests that each scientific concept consists of (...) three components of content: 1) reference, 2) inferential role, and 3) the epistemic goal pursued with the concept's use. I argue that in the course of history a concept can change in any of these three components, and that change in one component—including change of reference—can be accounted for as being rational relative to other components, in particular a concept's epistemic goal.This semantic framework is applied to two cases from the history of biology: the homology concept as used in 19th and 20th century biology, and the gene concept as used in different parts of the 20th century. The homology case study argues that the advent of Darwinian evolutionary theory, despite introducing a new definition of homology, did not bring about a new homology concept (distinct from the pre-Darwinian concept) in the 19th century. Nowadays, however, distinct homology concepts are used in systematics/evolutionary biology, in evolutionary developmental biology, and in molecular biology. The emergence of these different homology concepts is explained as occurring in a rational fashion. The gene case study argues that conceptual progress occurred with the transition from the classical to the molecular gene concept, despite a change in reference. In the last two decades, change occurred internal to the molecular gene concept, so that nowadays this concept's usage and reference varies from context to context. I argue that this situation emerged rationally and that the current variation in usage and reference is conducive to biological practice.The dissertation uses ideas and methodological tools from the philosophy of mind and language, the philosophy of science, the history of science, and the psychology of concepts. (shrink)

A common worry about the genetic engineering of human beings is that it will reduce human genetic diversity, creating a biological monoculture that could not only increase our susceptibility to disease but also hasten the extinction of our species. Thus far, however, the evolutionary implications of human genetic modification remain largely unexplored. In this paper, I consider whether the widespread use of genetic engineering technology is likely to narrow the present range of genetic variation, and if so, whether this would (...) in fact lead to the evolutionary harms that some authors envision. By examining the nature of biological variation and its relation to population immunity and evolvability, I show that not only will genetic engineering have a negligible impact on human genetic diversity, but also that it will be more likely to ensure rather than undermine the health and longevity of the human species. (shrink)

This paper aims at discussing some difficulties regarding the species definition problem in biology. I will try to show that typological concept defines species as fixed, immutable entities. After this, I will consider some passages of Origin of Species in the attempt to characterize Darwinian species as populations that may be modified, through natural processes, into new species. Besides, I will present the biological concept of species, trying to discuss prroblems of not making distinctions between species as classes and species (...) as concrete individuals. Then, I will point out some different definitions, alternative to the biological concept. Finally, I will delineate some consequences of species definition discussion to own human species (Homo sapiens). (shrink)

The species category is defined as thesmallest historical individual within which there is a parental pattern of ancestry and descent. The use of historical individual in this definition is consistent with the prevailing notion that speciesper se are not involved in processes — they are effects, not effectors. Reproductive isolation distinguishes biparental historical species from their parts, and it provides a basis for understanding the nature of the evidence used to discover historical individuals.

Throughout his career David Hull has sought to bring the philosophy of science into closer contact with science and especially with biological science (Hull 1969, 1997b). This effort has taken many forms. Sometimes it has meant ‘either explaining basic biology to philosophers or explaining basic philosophy to biologists’ (Hull 1996, p. 77). The first of these tasks, simple as it sounds, has been responsible for revolutionary changes. It is well known that traditional philosophy of science, modeled as it was on (...) theoretical physics, proved inadequate when philosophers turned their attention to biological science. Biological examples have driven major revisions of accounts of reduction (Hull 1974; Schaffner 1993, Ch. 9), laws of nature (Beatty et al. 1997), theories (Lloyd 1988) and natural kinds (Wilson 1999, Part III). Nor is explaining basic philosophy to biologists a task to be looked down upon. It is useful, not because philosophy has all the answers, but because scientists must think about how to do science, that is doing philosophy of science and scientists frequently reinvent philosophical views with known flaws. Early in his career Hull found biological systematists in the grip of a crude operationalism about scientific concepts and said so in the pages of Systematic Zoology (Hull 1968). For the next thirty years, as biologists debated the nature of species and the correct principles of classification, Hull added a philosophical note at the same congresses and in the same journals (Hull 1970, 1976, 1980, 1997a, 1999). (shrink)

Present-day thought on the notion of species is troubled by a mistaken understanding of the nature of the issue: while the species problem is commonly understood as concerning the epistemology and ontology of one single scientific concept, I argue that in fact there are multiple distinct concepts at stake. An approach to the species problem is presented that interprets the term ‘species’ as the placeholder for four distinct scientific concepts, each having its own role in biological theory, and an explanation (...) is given of the concepts involved. To illustrate how these concepts are commonly conflated, two widely accepted ideas on species are criticized: species individualism and species pluralism. I argue that by failing to distinguish between the four concepts and their particular roles in contemporary biological theory, these ideas stand in the way of a final resolution of the species problem. (shrink)

I defend the view that many biological categories are defined by homology against a series of arguments designed to show that all biological categories are defined, at least in part, by selected function. I show that categories of homology are `abnormality inclusive'—something often alleged to be unique to selected function categories. I show that classifications by selected function are logically dependent on classifications by homology, but not vice-versa. Finally, I reject the view that biologists must use considerations of selected function (...) to abstract away from variation and pathology to form a canonical description of a class of biological systems. (shrink)

There is an interesting parallel between two debates in different domains of contemporary analytic philosophy. One is the endurantism– perdurantism, or three-dimensionalism vs. four-dimensionalism, debate in analytic metaphysics. The other is the debate on the species problem in philosophy of biology. In this paper I attempt to cross-fertilize these debates with the aim of exploiting some of the potential that the two debates have to advance each other. I address two issues. First, I explore what the case of species implies (...) regarding the feasibility of particular positions in the endurantism– perdurantism debate. I argue that the case of species casts doubt on the recent claim that three-dimensionalism and four-dimensionalism are equivalent descriptions of the same underlying reality. Second, and conversely, I examine whether the metaphysical worry about three-dimensionalism and four-dimensionalism can help us to better understand the nature of biological species. I show that analyzing the thesis that species are individuals against the background of the endurantism– perdurantism debate allows us to explicate two different ways in which this thesis can be interpreted. (shrink)

Supervenience is a relationship which has been used recently to explain the physical determination of biological phenomena despite resistance to reduction. Supervenience, however, is plagued by ambiguities which weaken its explanatory value and obscure some interesting aspects of reduction in biology. Although I suspect that similar considerations affect the use of supervenience in ethics and the philosophy of mind, I don’t intend anything I have to say here to apply outside of the physical and biological cases I consider.The main point (...) of this paper is that there is a property of biological systems which makes it both misleading and inappropriate to reduce central biological phenomena to the properties of underlying components. Despite this, reductive explanation has been a major source of innovation in biological theory. The apparent tension can be resolved if underlying properties are explanatorily relevant to the higher level phenomena even though the latter are not strictly reducible to the former. Supervenience, I will argue, is not robust enough to deny reduction while supporting explanatory relevance. (shrink)

Concepts and methods originating in one discipline can distort the structure of another when they are applied to the latter. I exemplify this mostly with reference to systematic biology, especially problems which have arisen in relation to the nature of species. Thus the received views of classes, individuals (which term I suggest be replaced by units to avoid misunderstandings), and sets are all inapplicable, but each can be suitably modified. The concept of fuzzy set was developed to deal with species (...) and I defend its applicability. Taxa at all levels are real and participate in biological processes. Analysis of cause and pattern provides the deep structure in which metabiology is grounded; violation of this principle has led to diverse errors in biology. (shrink)

The thesis that species are individuals, and not classes as the traditional view had it, has been influential in the last 25 years. In this paper David Hull's arguments for the thesis are surveyed, as well as some counterarguments presented by Philip Kitcher. It is claimed that though species can be conceptualized as individuals, we are not compelled to view them in that way. The importance of the issue seems to have been somewhat exaggerated. However, it might happen that empirical (...) findings concerning species selection would strengthen the case for the thesis, thereby rendering it straightforwardly empirical. The applicability of teleological explanation is suggested as a criterion for biological individuality. (shrink)

What is the relationship between evolutionary contingency and diversity? The evolutionary contingency thesis emphasizes dependency relations and chance as the hallmarks of evolution. While contingency can be destructive of, for example, the fragile and complex dynamics in an ecosystem, I will mainly focus on the productive or causal aspect of contingency for a particular sort of diversity. There are many sorts of diversities: Gould is most famous for his diversity-to-decimation model, which includes disparate body plans distinguishing different phyla. However, structural (...) diversity construed more broadly spans scales, such as organization in and among cells, structural arrangements and biomechanics on various scales, and even the profile of ancestor-descendent relationships or community structure of interactions within ecosystems. By focusing on stochastic processes in contingent evolution, I argue that contingency causes structural diversity. Specifically, I focus on the plurality of structural types of cells, genetic codes, and phyla diversity as case studies. (shrink)

Although generally informed by an intimate knowledge of evolutionary biology and taxonomy, the controversy over the nature of species is clearly philosophical; it consists almost entirely of the clarification of old, and the invention of new arguments for or against calling the species category a class, The debate seems firmly divided between those, like Kitts and Bernier, who see homo sapiens as a class, and those, like Hull and Ghiselin, who see it as an individual. In the first case, particular (...) human beings are members; in the second case, parts. To the champions of class, the essentialists, each species can be defined by means of a unique set of necessary and sufficient conditions, and every organism can be placed without equivocation into a particular species. To the individualists, nothing could be further from the truth. As a contingent, product of evolution, each species shares that crucial characteristic of an individual, spacio-temporal identity; each is a chunk of genealogical nexus. (shrink)