Online research in philosophy

Against species essentialism Content Type Journal Article DOI 10.1007/s11016-010-9448-6 Authors Olivier Rieppel, Department of Geology, The Field Museum, 1400 South Lake Shore Drive, Chicago, IL 60605-2496, USA Journal Metascience Online ISSN 1467-9981 Print ISSN 0815-0796.

The history of biological systematics documents a continuing tension between classifications in terms of nested hierarchies congruent with branching diagrams (the ‘Tree of Life’) versus reticulated relations. The recognition of conflicting character distribution led to the dissolution of the scala naturae into reticulated systems, which were then transformed into phylogenetic trees by the addition of a vertical axis. The cladistic revolution in systematics resulted in a representation of phylogeny as a strictly bifurcating pattern (cladogram). Due to the ubiquity of character (...) conflict—at the genetic or morphological level, or at any level in between—some characters will necessarily have to be discarded ( qua noise) in favor of others in support of a strictly bifurcating phylogenetic tree. Pattern analysts will seek maximal congruence in the distribution of characters (ultimately of any kind) relative to a branching tree-topology; process explainers will call such tree-topologies into question by reference to incompatible evolutionary processes. Pattern analysts will argue that process explanations must not be brought to bear on pattern reconstruction; process explainers will insist that the reconstructed pattern requires a process explanation to become scientifically relevant, i.e., relevant to evolutionary theory. The core question driving the current debate about the adequacy of the ‘Tree of Life’ metaphor seems to be whether the systematic dichotomization of the living world is an adequate representation of the complex evolutionary history of global biodiversity. In ‘Questioning the Tree of Life’, it seems beneficial to draw at least four conceptual distinctions: pattern reconstruction versus process explanation as different epistemological approaches to the study of phylogeny; open versus closed systems as expressions of different kinds of population (species) structures; phylogenetic trees versus cladograms as representations of evolutionary processes versus patterns of relationships; and genes versus species as expressions of different levels of causal integration and evolutionary transformation. (shrink)

Species are generally considered to be the basic units of evolution, and hence to constitute spatio-temporally bounded entities. In addition, it has been argued that species also instantiate a natural kind. Evolution is fundamentally about change. The question then is how species can remain the same through evolutionary change. Proponents of the species qua individuals thesis individuate species through their unique evolutionary origin. Individuals, or spatio-temporally located particulars in general, can be bodies, objects, events, or processes, or a combination of (...) these. It is here argued that species are best understood as open or closed, causally integrated processual systems that also instantiate an historically conditioned homeostatic property cluster natural kind. (shrink)

Taking its clues from Popperian philosophy of science, cladistics adopted a number of assumptions of the empiricist tradition. These include the identification of a dichotomy between observation reports and theoretical statements and its subsequent abandonment on the basis of the insight that all observation reports are theory-laden. The neglect of the ‘context of discovery’, which is the step of theory (hypothesis) generation. The emphasis on coherentism in the ‘context of justification’, which is the step of evaluation of the relative merits (...) of alternative theories. The appeal to a total evidence approach in phylogenetic inference. And finally, a silence about causation, which results in an instrumentalist approach to phylogeny reconstruction. This paper explores how these empiricist assumptions are embedded in phylogenetic systematics, and why these assumptions are problematic for cladists (or any taxonomists). (shrink)

The theory and practice of contemporary comparative biology and phylogeny reconstruction (systematics) emphasizes algorithmic aspects but neglects a concern for the evidence. The character data used in systematics to formulate hypotheses of relationships in many ways constitute a black box, subject to uncritical assessment and social influence. Concerned that such a state of affairs leaves systematics and the phylogenetic theories it generates severely underdetermined, we investigate the nature of the criteria of homology and their application to character conceptualization in the (...) context of transformationist and generative paradigms. Noting the potential for indeterminacy in character conceptualization, we conclude that character congruence (the coherence of character statements) relative to a hierarchy is a necessary, but not a sufficient, condition for phylogeny reconstruction. Specifically, it is insufficient due to the lack of causal grounding of character hypotheses. Conceptualizing characters as homeostatic property cluster natural kinds is in accordance with the empirical practice of systematists. It also accounts for the lack of sharpness in character conceptualization, yet requires character identification and re-identification to be tied to causal processes. (shrink)

A long-standing debate has dominated systematic biology and the ontological commitments made by its theories. The debate has contrasted individuals and the part – whole relationship with classes and the membership relation. This essay proposes to conceptualize the hierarchy of higher taxa is terms of a hierarchy of homeostatic property cluster natural kinds (biological species remain largely excluded from the present discussion). The reference of natural kind terms that apply to supraspecific taxa is initially fixed descriptively; the extension of those (...) natural kind terms is subsequently established by empirical investigation. In that sense, classification precedes generalization, and description provides guidance to empirical investigation. The reconstruction of a hierarchy of (homeostatic property cluster) natural kinds is discussed in the light of cladistic methods of phylogeny reconstruction. (shrink)

The philosophy of pattern cladism has been variously explained by reference to the work of Louis Agassiz. The present study analyzes Agassiz's attempt to combine an empirical approach to the study of nature with an idealistic philosophy. From this emerges the problem of empiricism and of the isomorphy between the order of nature and human thinking. The analysis of the writings of Louis Agassiz serves as the basis for discussion of the reality of natural groups as postulated by pattern cladists.

The received view in philosophy of biology is that biological taxa (species and higher taxa) do not have essences. Recently some philosophers (Boyd, Devitt, Griffiths, LaPorte, Okasha, and Wilson) have suggested new forms of biological essentialism. They argue that according to these new forms of essentialism biological taxa do have essences. This paper critically evaluates the new biological essentialism. The paper’s thesis is that the costs of adopting the new biological essentialism are many, yet the benefits are none. So there (...) is no compelling reason to resurrect essentialism concerning biological taxa. (shrink)