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.

Many phylogenetic systematists have criticized the Biological Species Concept (BSC) because it distorts evolutionary history. While defenses against this particular criticism have been attempted, I argue that these responses are unsuccessful. In addition, I argue that the source of this problem leads to previously unappreciated, and deeper, fatal objections. These objections to the BSC also straightforwardly apply to other species concepts that are not defined by genealogical history. What is missing from many previous discussions is the (...) fact that the Tree of Life, which represents phylogenetic history, is independent of our choice of species concept. Some species concepts are consistent with species having unique positions on the Tree while others, including the BSC, are not. Since representing history is of primary importance in evolutionary biology, these problems lead to the conclusion that the BSC, along with many other species concepts, are unacceptable. If species are to be taxa used in phylogenetic inferences, we need a history-based species concept. (shrink)

Oaks exemplify problems with the reproductive species concept which motivate a reconsideration of the use and nature of species. Ecology is important in the reconsideration. The species level is usually overemphasized in evolutionary thought; selection acts on phenotypes and any mutualistic units. Standard definitions tend to inhibit free conceptual progress. Multispecies, sets of broadly sympatric species that exchange genes, may occur among animals as well as plants and may conceivably bridge kingdoms. This phenomenon can be adaptively (...) important. There may be taxa without species. The degree of modality of adaptive zones can be investigated empirically. (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)

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)

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)

The so-called ‘‘species problem’’ has plagued evolution- ary biology since before Darwin’s publication of the aptly titled Origin of Species. Many biologists think the problem is just a matter of semantics; others complain that it will not be solved until we have more empirical data. Yet, we don’t seem to be able to escape discussing it and teaching seminars about it. In this paper, I briefly examine the main themes of the biological and philosophical liter- atures (...) on the species problem, focusing on identifying common threads as well as relevant differences. I then argue two fundamental points. First, the species problem is not primarily an empirical one, but it is rather fraught with philosophical questions that require—but cannot be settled by—empirical evidence. Second, the (dis-)solution lies in explicitly adopting Wittgenstein’s idea of ‘‘family resemblance’’ or cluster concepts, and to consider spe- cies as an example of such concepts. This solution has several attractive features, including bringing together apparently diverging themes of discussion among bio- logists and philosophers. The current proposal is con- ceptually independent (though not incompatible) with the pluralist approach to the species problem advocated by Mishler, Donoghue, Kitcher and Dupre ́, which implies that distinct aspects of the species question need to be emphasized depending on the goals of the researcher. From the biological literature, the concept of species that most closely matches the philosophical discussion pre- sented here is Templeton’s cohesion idea. (shrink)

This paper examines the species problem in microbiology and its implications for the species problem more generally. Given the different meanings of ‘species’ in microbiology, the use of ‘species’ in biology is more multifarious and problematic than commonly recognized. So much so, that recent work in microbial systematics casts doubt on the existence of a prokaryote species category in nature. It also casts doubt on the existence of a general species category for (...) all of life (one that includes both prokaryotes and eukaryotes). Prokaryote biology also undermines recent attempts to save the species category, such as the suggestion that species are metapopulation lineages and the idea that ‘species’ is a family resemblance concept. (shrink)

At least three different issues are commonly referred to by the term “the species problem”: one concerns the necessary properties of species, a second the processes responsible for the existence of species, and a third methods for inferring species limits. Solutions have recently been proposed to the first two problems, which are conceptual in nature (the third is methodological). The first equates species with metapopulation lineages and proposes that existence as a separately evolving metapopulation (...) lineage be considered the only necessary property of species. The second views the species category as a cluster concept and proposes that no single process or set of processes be considered necessary for the existence of species. Although these two solutions have been portrayed as being in conflict, they are, in fact, highly compatible. Moreover, the proposals in question clarify the problem concerning methods for inferring the limits of species, which has for a long time been confused with the problem concerning the necessary properties of species. Together these proposals provide the opportunity for biology to move beyond debates about the definition of the species category and focus on estimating the boundaries and numbers of species as well as studying the diverse processes involved in their origin and persistence. BioEssays 27:1263–1269, 2005. © 2005 Wiley Periodicals, Inc. (shrink)

This chapter contains sections titled: Introduction Early Species Concepts—Linnaeus Biological Species Concepts Phylogenetic Species Concepts Species Concepts and Speciation Conclusions Postscript: Counterpoint References.

Frank E. Zachos offers a comprehensive review of one of today's most important and contentious issues in biology: the species problem. After setting the stage with key background information on the topic, the book provides a brief history of species concepts from antiquity to the Modern Synthesis, followed by a discussion of the ontological status of species with a focus on the individuality thesis and potential means of reconciling it with other philosophical approaches. More than (...) 30 different species concepts found in the literature are presented in an annotated list, and the most important ones, including the Biological, Genetic, Evolutionary and different versions of the Phylogenetic Species Concept, are discussed in more detail. Specific questions addressed include the problem of asexual and prokaryotic species, intraspecific categories like subspecies and Evolutionarily Significant Units, and a potential solution to the species problem based on a hierarchical approach that distinguishes between ontological and operational species concepts. A full chapter is dedicated to the challenge of delimiting species by means of a discrete taxonomy in a continuous world of inherently fuzzy boundaries. Further, the book outlines the practical ramifications for ecology and evolutionary biology of how we define the species category, highlighting the danger of an apples and oranges problem if what we subsume under the same name ("species") is in actuality a variety of different entities. A succinct summary chapter, glossary and annotated list of references round out the coverage, making the book essential reading for all biologists looking for an accessible introduction to the historical, philosophical and practical dimensions of the species problem. (shrink)

Species concepts for bacteria and other microbes are contentious, because they are often asexual. There is a Problem of Homogeneity: every mutation in an asexual lineage forms a new strain, of which all descendents are clones until a new mutation occurs. We should expect that asexual organisms would form a smear or continuum. What causes the internal homogeneity of asexual lineages, if they are in fact homogeneous? Is there a natural “species concept” for “microbes”? Two main (...) concepts devised for metazoans and metaphytes have been applied to bacteria. One is the Recombination Concept, a revised form of the Biological Species Concept in which the homogenizing mechanism is the sharing of genome fragments, somewhat akin to sexual recombination. The other is the Ecological Species Concept, in which the ecological niche is that which maintains lineages as cohesive. In this paper I will discuss these two concepts, and offer an underlying model that conjoins them, and consider the implications for species concepts in general. In short, my argument is that asexual species are instances of the most primitive and underived notion of species, which I will call “quasispecies”, following Eigen, and that sexual species are merely one derived kind of species. Moreover, I will argue that there is a continuum of recombination from simple viral models in which each strain is a clone, through to obligate recombination of 50% of the parents’ genome, and that consequently there is no sharp division between “microbial” and more familiar species. (shrink)

The species problem is often described as the abundance of conflicting definitions of _species_, such as the biological species concept and phylogenetic species concepts. But biologists understand the notion of species in a non-definitional as well as a definitional way. In this article I argue that when they understand _species_ without a definition in their mind, their understanding is often mediated by the notion of _good species_, or prototypical species, as the idea of (...) ``prototype'' is explicated in cognitive psychology. This distinction helps us make sense of several puzzling phenomena regarding biologists' dealing with species, such as the fact that in everyday research biologists often behave as if the species problem is solved, while they should be fully aware that it is not. I also briefly discuss implications of this finding, including that some extant attempts to answer what the nature of species is have an inadequate assumption about how the notion of species is represented in biologists' minds. (shrink)

Traditionally, species have been treated by biologists and philosophers as natural kinds. However, this conception of species has posed several problems for evolutionary theory. For example, biologists have been hard pressed to find traits had by all and only the members of a species. This has caused some philosophers to doubt that evolutionary theory is a scientific theory. ;In an effort to resolve such problems, Michael Ghiselin and David Hull have argued that species are not kinds (...) but individuals. A number of authors have adopted this conclusion. Some have even gone on to argue that besides showing that species are not kinds, the thesis that species are individuals has other ramifications for evolutionary theory. For example, the thesis is said to lend support to the Theory of Punctuated Equilibrium. ;In my dissertation, I argue that while species are not kinds, most species are not individuals either. Furthermore, even if all species were individuals, the alleged ramifications are not forthcoming. ;More specifically, in Chapter One I review the arguments against species being kinds and the recent replies to those arguments. I also examine the nature of kinds and contend that the original arguments against species being kinds still stand. ;In Chapter Two, I turn to the metaphysics of individuality. I argue that mere spatiotemporal continuity and a rough similarity among the constituents of an entity are insufficient for it to be an individual. The constituents of an individual must be appropriately causally connected as well. ;With this requirement, I return to species in Chapter Three. Most species consist of subpopulations which are not causally connected in any biological fashion. Because of this, and other reasons, I argue that most species are not individuals. ;In the final chapter, I point out that the result of the previous chapter goes against the claim that what distinguishes species from higher taxa is that species and not higher taxa are individuals. I also argue that even if all species were individuals, their individuality does not support the Theory of Punctuated Equilibrium. Finally, some authors maintain that a unit of selection must be an individual. I argue that there is no such requirement on units of selection. (shrink)

The new millennium has opened with a perfectly splendid decade of scholarship relating to the ‘Species Problem’. So, at least we now have a clear idea of what this is, but still no clear solution that will suit both biologists and philosophers. Richards has recently attempted to capture this story and to fill the void with two projects in one book. The first project is a descriptive and analytical history of the problem, which provides links to other (...) recent works and thereby allows one to fully reconstruct the literature. The second is prescriptive and presents Richards’s solution via a ‘division of labour in a conceptual framework’ followed by recapitulation and conclusions. It is my assessment as presented here that the first project will appeal more to biologists and the second one to philosophers. There is much of value in Richards approach including an excellent evaluation of the essentialism story in the descriptive project and clear exposition of several key issues such as the ‘species-as-individuals’ versus ‘species-as-categories’ debate which are covered in the second project. Interesting and informative as these arguments undoubtedly are, something still seems to be missing here. In this essay I suggest that this perception arises from Richards’ failure to embrace ideas about the importance of relativity and contingency in species definitions and further that his new conceptual framework lacks one hierarchical level to link overarching lineage concepts of species as evolutionary units with practical definitions for their recognition. In my view, the missing link is reproductive isolation and I conclude my review by presenting a prescriptive project for biologists to balance the one that Richards has delivered to philosophers. (shrink)

Species, or ‘the Species Problem’, is a topic in science, in the philosophy of science, and in general philosophy. There is not one, but many, species problems, and these are dealt with in this volume. Species are often thought of as units of biology, to be used in ecology, conservation, classification, and theory. The chapters in this book present opposing views on the current philosophical and conceptual issues of the Species Problem in biology. (...) -/- Divided into four sections Theories and Concepts, Practice and Methods, Ranks, Trees and Names, and Metaphysics and Epistemologies, the book is authored by systematists, philosophers, historians and working biologists, many leaders in their fields. Topics include Essentialism and individuals, speciation modes, theory and the species rank, nomenclature and diagnosis, scale of species, and ecology, conservation, and species. -/- Species Problems and Beyond aims to clarify the contemporary issues of the Species Problem. It is ideal for use in upper-level seminars and courses in Evolutionary Biology, Philosophy of Science, Philosophy of Biology, Systematics and Taxonomy, and Phylogenetics/Cladistics, and for any scholar in these fields. (shrink)

There is long-standing disagreement among systematists about how to divide biodiversity into species. Over twenty different species concepts are used to group organisms, according to criteria as diverse as morphological or molecular similarity, interbreeding and genealogical relationships. This, combined with the implications of evolutionary biology, raises the worry that either there is no single kind of species, or that species are not real. This book surveys the history of thinking about species from Aristotle to (...) modern systematics in order to understand the origin of the problem, and advocates a solution based on the idea of the division of conceptual labor, whereby species concepts function in different ways - theoretically and operationally. It also considers related topics such as individuality and the metaphysics of evolution, and how scientific terms get their meaning. This important addition to the current debate will be essential for philosophers and historians of science, and for biologists. (shrink)

This chapter explores the relevance of insights drawn from the Continental tradition of PhenomenologyPhenomenology for the solution of the long-standing “species problem” in the philosophy of biology. Returning to the roots of Continental PhenomenologyPhenomenology in the work of Edmund HusserlHusserl, Edmund, rather than to its later developments, the paper situates the discussion of the species concept in relation to the concepts of “intentionality” andIntentionalitythe “life-worldLife-world” as developed by HusserlHusserl, Edmund. Current conflicts surrounding the interpretation of the (...) meaning of “species” in biological discourse are described in terms of two different intentional “thematizings” of the life-worldLife-world, both of which satisfy theoretical scientific interests. One of these deals with the interest in the synchronic classificationClassification of the world. The other concerns the diachronic historical development of life. It is argued that this Phenomenological analysis give a more satisfactory interpretation of the species problem than that which has been generated by conflicts between advocates of “individualist” and “class” conceptions of natural species. The larger goal of this chapter is to highlight the importance of Jean Gayon’s work in developing a dialogue between Continental and Analytic approaches to the philosophy of biology. (shrink)

The species problem is one of the oldest controversies in natural history. Its persistence suggests that it is something more than a problem of fact or definition. Considerable light is shed on the species problem when it is viewed as a problem in the representation of the natural system (sensu Griffiths, 1974, Acta Biotheor. 23: 85–131; de Queiroz, 1998, Philos. Sci. 55: 238–259). Just as maps are representations of the earth, and are subject to (...) what is called cartographic generalization, so diagrams of the natural system (evolutionary trees) are representations of the evolutionary chronicle, and are subject to a temporal version of cartographic generalization which may be termed systematic generalization. Cartographic generalization is based on judgements of geographical importance, and systematic generalization is based on judgements of historical importance, judgements expressed in narrative sentences (sensu Danto, 1985, Narration and knowledge, Columbia Univ. Press, New York). At higher systematic levels these narrative sentences are conventional and retrospective, but near the "species" level they become prospective, that is, dependent upon expectations of the future. The truth of prospective narrative sentences is logically indeterminable in the present, and since all the common species concepts depend upon prospective narration, it is impossible for any of them to be applied with precision. (shrink)

The phylogenetic species concept is applied for the first time to a major radiation of birds, the birds-of-paradise (Paradisaeidae) of Australasia. Using the biological species concept, previous workers have postulated approximately 40–42 species in the family. Of these, approximately 13 are monotypic and 27 are polytypic with about 100 subspecies. Phylogenetic species are irreducible (basal) clusters of organisms (terminal taxa) that are diagnosably distinct from other such clusters. Within the context of this concept, approximately 90 (...) species of paradisaeids are postulated to have diversified within Australasia. The phylogenetic species concept more accurately describes evolutionary diversity within the family and provides a better theoretical and empirical framework for analysing speciation, historical biogeography and patterns of morphological, behavioral and ecological diversification within this group than does the biological species concept. (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)

Darwin offered an intriguing answer to the species problem. He doubted the existence of the species category as a real category in nature, but he did not doubt the existence of those taxa called ‘‘species’’. And despite his scepticism of the species category, Darwin continued using the word ‘‘species’’. Many have said that Darwin did not understand the nature of species. Yet his answer to the species problem is both theoretically (...) sound and practical. On the theoretical side, DarwinÕs answer is confirmed by contemporary biology, and it offers a more satisfactory answer to the species problem than recent attempts to save the species category. On the practical side, DarwinÕs answer frees us from the search for the correct theoretical definition of ‘‘species’’. But at the same time it does not require that we banish the word ‘‘species’’ from biology as some recent sceptics of the species category advocate. Ó The Willi Hennig Society 2010. (shrink)

Developments in genetic engineering may soon allow biologists to clone organisms from extinct species. The process, dubbed “de-extinction,” has been publicized as a means to bring extinct species back to life. For theorists and philosophers of biology, the process also suggests a thought experiment for the ongoing “species problem”: given a species concept, would a clone be classified in the extinct species? Previous analyses have answered this question in the context of specific de-extinction technologies (...) or particular species concepts. The thought experiment is given more comprehensive treatment here. Given the products of three de-extinction technologies, twenty-two species concepts are “tested” to see which are consistent with the idea that species may be resurrected. The ensuing discussion considers whether or not de-extinction is a conceptually coherent research program and, if so, whether or not its development may contribute to a resolution of the species problem. Ultimately, theorists must face a choice: they may revise their commitments to species concepts or they may recognize de-extinction as a means to make progress in the species problem. (shrink)

The biological species (biospecies) concept applies only to sexually reproducing species, which means that until sexual reproduction evolved, there were no biospecies. On the universal tree of life, biospecies concepts therefore apply only to a relatively small number of clades, notably plants andanimals. I argue that it is useful to treat the various ways of being a species (species modes) as traits of clades. By extension from biospecies to the other concepts intended to capture (...) the natural realities of what keeps taxa distinct, we can treat other modes as traits also, and so come to understand that theplurality of species concepts reflects the biological realities of monophyletic groups.We should expect that specialists in different organisms will tend to favour those concepts that best represent the intrinsic mechanisms that keep taxa distinct in their clades. I will address the question whether modes ofreproduction such as asexual and sexual reproduction are natural classes, given that they are paraphyletic in most clades. (shrink)

In biological systematics, as well as in the philosophy of biology, species and higher taxa are individuated through their unique evolutionary origin. This is taken by some authors to mean that monophyly is a (relational) property not only of higher taxa, but also of species. A species is said to originate through speciation, and to go extinct when it splits into two daughter species (or through terminal extinction). Its unique evolutionary origin is said to (...) bestow identity on a species through time and change, and to render species names rigid designators. Species names are thus believed to function just like names of supraspecific taxa. However, large parts of the Web of Life are composed of species that do not have a unique evolutionary origin from a single population, lineage or stem-species. Further, monophyly is an ambiguous concept if it is defined simply in terms of ‘unique evolutionary origin’. Disambiguating the concept by defining a monophyletic taxon as ‘a taxon that includes the ancestor and all, and only, its descendant’ renders monophyly inapplicable to species. At the heart of the problem lies a fundamental distinction between species and monophyletic taxa, where species form mutually exclusive reticulated systems, while higher taxa form inclusive hierarchical systems. Examples are given both at the species level and below to illustrate the problems that result from the application of the monophyly criterion to species. The conclusion is that the concepts of exclusivity and monophyly should be treated as non-overlapping: exclusivity marks out a species synchronistically, i.e. in the present time. Monophyly marks out clades (groups of species) diachronistically, i.e. within an historical dimension. (shrink)

In the last thirty years systematics has transformed itself from a discipline concerned with classification into a discipline concerned with reconstructing the evolutionary history of life. This transformation has been driven by cladistic analysis, a set of techniques for reconstructing evolutionary trees. Long interested in the large-scale structure of evolutionary history, cladistically oriented systematists have recently begun to apply "tree thinking" to problems near the species level. ¶ In any local ("non-dimensional") situation species are usually well-defined, but across (...) space and time the grouping of populations into species is often problematic. Three views of species are in common use today, the biological species concept, the evolutionary species concept, and the phylogenetic species concept. Each of these has strengths and weaknesses, but no matter which is applied, exact counts of the number of species in any extended area will always be ambiguous no matter how much factual information is available. This ambiguity arises because evolution is an historical process, and the grouping of organisms into species always depends to some extent upon expectations of the future behavior of those organisms and their descendants, expectations that cannot be evaluated in the present. The existence and special character of the species problem is itself one of the central pieces of evidence for evolution. (shrink)

The species concept is one of the oldest and most fundamental in biology. And yet it is almost universally conceded that no satisfactory definition of what constitutes a species has ever been proposed. The present article is devoted to an attempt to review the status of the problem from a methodological point of view. Since the species is one of the many taxonomic categories, the question of the nature of these categories in general needs to be (...) entered into. (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)

In this article, I argue that species are mutable in Hegel’s philosophy of biology. While scholars have argued for the compatibility of Hegel’s philosophy and Darwin’s theory of evolution, none have dealt with the ontological status of species in their respective accounts. In order to make the case that for Hegel species are mutable, I first deal with a textual problem that in the 1827 edition of the Encyclopedia, the species concept appears after the sexual (...) relationship, whereas in the 1830 edition it appears prior. I argue that these different sequences entail different models for the species concept. By examining the conceptual development leading up to the account of species, on the one hand, and contemporary biological accounts of the status of species on the other, I argue that the 1827 model is more consistent both with Hegel’s method and with the species concept of contemporary biology. (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)

This paper isolates a hard, long-standing species problem: developing a comprehensive and exacting theory about the constitutive conditions of the species category, one that is accurate for most of the living world, and which vindicates the widespread view that the species category is of more theoretical import than categories such as genus, sub-species, paradivision, and stirp. The paper then uncovers flaws in several views that imply we have either already solved that hard species (...) class='Hi'>problem or dissolved it altogether – so-called We Are Done views. In doing so the paper offers new criticisms of the general lineage species concept (GLSC), evolutionary species concept (EvSC), biological species concept (BSC), other similar concepts, Ereshefsky’s eliminative pluralism about the species category, and both Mishler’s pessimism and Wilkins’ phenomenalism about that category. Opposed to We Are Done views, the paper argues for a Revving Up view, on which we are nearly ready to begin the hard species problem in earnest. To help work towards these conclusions, the paper begins with an outline of a new kind of view of species (Barker 2019a), which proposes they are feedback systems of a mathematically specifiable and empirically testable sort. (shrink)

A number of authors argue that while species are evolutionary units, individuals and real entities, higher taxa are not. I argue that drawing the divide between species and higher taxa along such lines has not been successful. Common conceptions of evolutionary units either include or exclude both types of taxa. Most species, like all higher taxa, are not individuals, but historical entities. Furthermore, higher taxa are neither more nor less real than (...) class='Hi'>species. None of this implies that there is no distinction between species and higher taxa; the point is that such a distinction is more subtle than many authors have claimed. (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)

The species problem is the longstanding puzzle regarding the nature of species. This paper aims to describe how biologists experience little communication breakdown when they have different conceptions of species. For this purpose, I analyze two debates on species and speciation between Guy Bush and Jerry Coyne & H. Allen Orr. Although they have radically different ideas on species, they experience little communication difficulty. I will argue that this is because they implicitly agreed on (...) the referent of the group of organisms being addressed and possible causal factors of the speciation process. This analysis confirms a leading account in the general philosophy of science on the way in which scientists avoid the incommensurability threat. (shrink)

Do biological species have essences? The debate over this question in philosophy of biology exhibits fundamental confusion both between and within authors. In What to Salvage from the Species Essentialism Debate, I argue that the best way forward is to drop the question and its terms in order to make progress on two issues: how to individuate species taxa; and how to make sense of changes in explanatory frameworks across the Darwinian historical divide. I further argue (...) that a primary motivation for anti-essentialism, biological variation, matters differently to each project. Anti-essentialism in the philosophy of biology has inspired influential rejections of the idea that there is such a thing as human nature. In More Bark than Bite, I show that the arguments are significantly weaker than supposed. Moreover, none of the weighty consequences thought to follow from any genuine sense in which there is no human nature, actually do follow. The evolution-based denial of human nature has little to contribute to inquiries into the human condition, both philosophical and scientific. Decisions about whether to undergo experiences that could change the very preference-base on which the choice is made are “transformative”. L. A. Paul argues that transformative decisions present a problem for standard decision theory when approached in a way that leans on evaluations of the experiential consequences of the choices. Her solution proposes that we approach such decisions by asking ourselves how much we value the kind of discovery involved in transformative experience. In Shifting Attention on Transformative Choice, I present two problems for her solution and offer an alternative. Transformative decisions may be rationally approached by asking ourselves how much we judge the activities on the other side of transformation to be worthwhile. This proposal helps make better sense of our relationship to experiential consequences of transformation, which is more flexible than Paul acknowledges. (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)

The idea of naturalizing metaphysics stretches back to Locke and Newton. Recently it has been revived by Ross and Ladyman et al (2007) in ‘Every Thing Must Go’. At the heart of the doctrine is the idea that metaphysics should be constrained by actual science (science which is current and institutionally valid). It is my attempt in this paper to naturalize the metaphysics of the species problem by proposing a species concept which conforms to the principles set (...) out in Ross and Ladyman et al's book. This is a concept which conforms strictly with current work in the field of evolutionary theory, with specific reference to theories in Information theory and Thermodynamics. In the end I use as an example of non-naturalized metaphysics Matthew Slater's paper ‘The Indeterminacy Problem for Species as Individuals’. (shrink)

Historiography is becoming more critical of the typology/ population dichotomy introduced by Ernst Mayr. Therefore, one should look again at the problem of species in non-Darwinian theories: neo-Lamarckism and orthogenesis, and consider the possibility that this problem was overly simplified. What can be seen in both of them is the existence of a tension between the idea of evolution and the essence of species. In neo-Lamarckism, this tension was resolved by recognizing species as static entities (...) which changed only when triggered by external stimulus. In orthogenesis, evolution was seen as constant phenomena and species – as naturally changeable entities. However, orthogeneticists assumed that not only species, but also whole phyletic lines had essences that constrained their further evolution. Thus, in both cases we can see interpretation of species in tune with essentialism, but essentialism is widely differently integrated with each of these concepts of evolution. (shrink)

This paper seeks to propose a direction of research based upon the transformation of Merleau-Ponty's thinking with respect to animal life over the course of his writings. In his earlier works, Merleau-Ponty takes up the position that “life” does not mean the same thing when applied to an animal and a human being because of the manner in which the “human dialectic” alters the human being's relation to life. In his later works, particularly in his lectures on nature, this position (...) softens so that the relationship between animals and humans becomes non-hierarchical, but remains essentially the same: there may be no “rupture” between humans and animals, but they are still essentially distinct insofar as all non-humans can be grouped into a single class of “animality.” I attempt to show that Merleau-Ponty fails to follow through with his most radical insights with respect to the relationships between living beings by preserving this distinction and suggest some ways in which we might today confront this problem through the works of Merleau-Ponty in a way that he did not. The proposal, then, is to take seriously “dialectical” biology and develop a Merleau-Pontian conception of species based upon the interrelations of living beings and their environments rather than focusing solely on organisms as discrete units. The conclusion then considers what the consequences of this understanding might be for our understanding of Merleau-Ponty's ontology in general. (shrink)

This paper outlines an alternative perspective on species that avoids some of the underlying assumptions held by the BSC and other gene-centred species concepts. It begins with a characterisation of the species problem and some of the assumptions underpinning conceptions of species. In particular, the underlying bias of some conceptions (such as the BSC) to focus exclusively on the adult stage of the life cycle in articulating what a species is.

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 are considered the basic unit of biological classification and evolution. Hence, they are used as a benchmark in several fields, although the ontological status of such a category has always been a matter of debate. This paper aims to discuss the problem of the definition of species within the new mechanistic approach. Nevertheless, the boundary between entities, activities, and mechanisms remains difficult to establish and always requires an analysis of what is meant by explanation. As a (...) case study, the paper describes the debate concerning the species category by considering different kingdoms: Animals, Bacteria, and Fungi. The inherently biological differences between those groups prevent the use of a single, universally applicable concept of species that could fit the mechanisms responsible for the variability present in these kingdoms. The same issue is encountered within each group, as highlighted through a focus on mammals and microbes. This controversy has given rise to opposite approaches, namely: monism, which looks for a single definition that might account for all species, and pluralism, which admits that different groups of organisms require somewhat different definitions. In order to develop an adequate definition of species, we propose to apply a new mechanistic framework, which considers the ontic-epistemic dimensions of scientific explanation in close parallel. The apt correlation between epistemic and the ontic aspects highlights the way in which the concept of species and the reference to data are strictly co-determined. This suggests that the concept of species is better understandable within a dual ontic-epistemic approach. (shrink)

The taxa that appear in biological classifications are commonly seen as representing information about the traits of their member organisms. This paper examines in what way taxa feature in the storage and retrieval of such information. I will argue that taxa do not actually store much information about the traits of their member organisms. Rather, I want to suggest, taxa should be understood as functioning to localize organisms in the genealogical network of life on Earth. (...) class='Hi'>Taxa store information about where organisms are localized in the network, which is important background information when it comes to establishing knowledge about organismal traits, but it is not itself information about these traits. The view of species and higher taxa that is proposed here follows from examining three problems that occur in contemporary biological systematics and are discussed here: the problem of generalization over taxa, the problem of phylogenetic inference, and the problematic nature of the Tree of Life. (shrink)

The taxa that appear in biological classifications are commonly seen as representing information about the traits of their member organisms. This paper examines in what way taxa feature in the storage and retrieval of such information. I will argue that taxa do not actually store much information about the traits of their member organisms. Rather, I want to suggest, taxa should be understood as functioning to localize organisms in the genealogical network of life on Earth. (...) class='Hi'>Taxa store information about where organisms are localized in the network, which is important background information when it comes to establishing knowledge about organismal traits, but it is not itself information about these traits. The view of species and higher taxa that is proposed here follows from examining three problems that occur in contemporary biological systematics and are discussed here: the problem of generalization over taxa, the problem of phylogenetic inference, and the problematic nature of the Tree of Life. (shrink)

The concept of species is one of the core concepts in biology and one of the cornerstones of evolutionary biology, yet it is rife with conceptual problems. Philosophers of biology have been discussing the concept of species for decades, and in doing so they sometimes appeal to the views of biologists. However, their statements as to what biologists think are seldom supported by empirical data. In order to investigate what biologists actually think about the key issues related (...) to the problem of species, we have conducted a survey on the sample of 193 biologists from the population of biologists from over 150 biology departments at universities in the US and the EU. This article presents and discusses the results of the survey. Some results confirm and others falsify the reiterated statements of philosophers of biology as to what biologists think, but all results we obtained should be informative and relevant for future discussions of the problem of species. (shrink)