Why has it been so difficult to integrate paleontology and mainstream evolutionary biology? Two common answers are: (1) the two fields have fundamentally different aims, and (2) the tensions arise out of disciplinary squabbles for funding and prestige. This paper examines the role of fossil data in phylogeny reconstruction in order to assess these two explanations. I argue that while cladistics has provided a framework within which to integrate fossil character data, the stratigraphic (temporal) component of fossil data has been (...) harder to integrate. A close examination of how fossil data have been used in phylogeny reconstruction suggests that neither explanation is adequate. While some of the tensions between the fields may be intellectual turf wars, the second explanation downplays the genuine difficulty of combining the distinctive data of the two fields. Furthermore, it is simply not the case that the two fields pursue completely distinct aims. Systematists do disagree about precisely how to represent phylogeny (e.g., minimalist cladograms or trees with varying levels of detail) but given that every tree presupposes a pattern of branching (a cladogram), these aims are not completely distinct. The central problem has been developing methods that allow scientists to incorporate the distinctive bodies of data generated by these two fields. Further case studies will be required to determine if this explanation holds for other areas of interaction between paleontology and neontology. (shrink)

The goal of cladistic systematics is to discern sister-group relations (cladistic relations) by the methods of cladistic analysis and to represent them explicitly and unambiguously in cladograms and cladistic classifications. Cladists have selected cladistic relations to represent for two reasons: cladistic relations can be discerned with reasonable certainty by the methods of cladistic analysis and they can be represented with relative ease in cladograms and classifications. Cladists argue that features of phylogeny other than cladistic relations cannot be discerned (...) with sufficient certainty to warrant attempting to represent them in either cladograms or classifications and could not be represented if they could. I argue that a better alternative is to work toward improving methods of cladistic analysis (or else to supplement them with other methods) so that such features of phylogeny can be discerned and to devise methods of representation capable of representing them in both cladograms and classifications. However, cladograms and classifications cannot represent everything about phylogeny. It is better to represent one or two aspects of phylogeny explicitly and unambiguously than nothing at all. (shrink)

Tree diagrams are the prevailing form of visualization in biological classification and phylogenetics. Already during the time of the so-called Systematist Wars from the mid-1960s until the 1980s most journal articles and textbooks published by systematists contained tree diagrams. Although this episode of systematics is well studied by historians and philosophers of biology, most analyses prioritize scientific theories over practices and tend to emphasize conflicting theoretical assumptions. In this article, I offer an alternative perspective by viewing the conflict through the (...) lens of representational practices with a case study on tree diagrams that were used by numerical taxonomists (phenograms) and cladists (cladograms). I argue that the current state of molecular phylogenetics should not be interpreted as the result of a competition of views within systematics. Instead, molecular phylogenetics arose independently of systematics and elements of cladistics and phenetics were integrated into the framework of molecular phylogenetics, facilitated by the compatibility of phenetic and cladistic practices with the quantitative approach of molecular phylogenetics. My study suggests that this episode of scientific change is more complex than common narratives of battles and winners or conflicts and compromises. Today, cladograms are still used and interpreted as specific types of molecular phylogenetic trees. While phenograms and cladograms represented different forms of knowledge during the time of the Systematist Wars, today they are both used to represent evolutionary relationships. This indicates that diagrams are versatile elements of scientific practice that can change their meaning, depending on the context of use within theoretical frameworks. (shrink)

This article reports the results of an experiment involving 108 college students with varying backgrounds in biology. Subjects answered questions about the evolutionary history of sets of hominid and equine taxa. Each set of taxa was presented in one of three diagrammatic formats: a noncladogenic diagram found in a contemporary biology textbook or a cladogram in either the ladder or tree format. As predicted, the textbook diagrams, which contained linear components, were more likely than the cladogram formats to yield explanations (...) of speciation as an anagenic process, a common misconception among students. In contrast, the branching cladogram formats yielded more appropriate explanations concerning levels of ancestry than did the textbook diagrams. Although students with stronger backgrounds in biology did better than those with weaker biology backgrounds, they generally showed the same effects of diagrammatic format. Implications of these results for evolution education and for diagram design more generally are discussed. (shrink)

This paper addresses the general problem of how to rationally choose an algorithm for phylogenetic inference. Specifically, the controversy between maximum likelihood (ML) and maximum parsimony (MP) perspectives is reframed within the philosophical issue of theory choice. A Kuhnian approach in which rationality is bounded and value-laden is offered and construed through the notion of a Style of Modeling. A Style is divided into four stages: collecting remnant models, constructing models of taxonomical identity, implementing modeling algorithms, and finally inferring and (...) confirming evolutionary trees or cladograms. The identification and investigation of styles is useful for exploring sociological and epistemological issues such as individuating scientific communities and assessing the rationality of algorithm choice. Regarding the last point, this paper suggests that the values motivating ML and MP perspectives are justified but only contextually; these algorithms also have normative force because they can be therapeutic by allowing us to rationally choose among several competing trees, nonetheless this force is limited and cannot be used in order to decide the controversy tout court. (shrink)

This paper addresses the general problem of how to rationally choose an algorithm for phylogenetic inference. Specifically, the controversy between maximum likelihood (ML) and maximum parsimony (MP) perspectives is reframed within the philosophical issue of theory choice. A Kuhnian approach in which rationality is bounded and value-laden is offered and construed through the notion of a Style of Modeling. A Style is divided into four stages: collecting remnant models, constructing models of taxonomical identity, implementing modeling algorithms, and finally inferring and (...) confirming evolutionary trees or cladograms. The identification and investigation of styles is useful for exploring sociological and epistemological issues such as individuating scientific communities and assessing the rationality of algorithm choice. Regarding the last point, this paper suggests that the values motivating ML and MP perspectives are justified but only contextually; these algorithms also have normative force because they can be therapeutic by allowing us to rationally choose among several competing trees, nonetheless this force is limited and cannot be used in order to decide the controversy tout court. (shrink)

Molecular methods have revolutionised virtually every area of biology, and metazoan phylogenetics is no exception: molecular phylogenies, molecular clocks, comparative phylogenomics, and developmental genetics have generated a plethora of molecular data spanning numerous taxa and collectively transformed our understanding of the evolutionary history of animals, often corroborating but at times opposing results of more traditional approaches. Moreover, the diversity of methods and models within molecular phylogenetics has resulted in significant disagreement among molecular phylogenies as well as between these and earlier (...) phylogenies. How should this broad and multifaceted problem be tackled? I argue that the answer lies in integrating evidence to infer the best evolutionary scenario. I begin with an overview of recent development in early metazoan phylogenetics, followed by a discussion of key conceptual issues in phylogenetics revolving around phylogenetic evidence, theory, methodology, and interrelations thereof. I then argue that the integration of different kinds of evidence (e.g. molecular, morphological, ecological) is necessary for arriving at the best evolutionary scenario (causal explanation) rather than merely the best-fitting cladogram (statistical explanation). Finally, I discuss the prospects of this view in stimulating interdisciplinary cross-talk in early metazoan research and beyond, and challenges that need to be overcome. (shrink)

Three experiments, adopting an evolutionary biology perspective, investigated subjects’ inferences about living things. Subjects were told that different enzymes help regulate cell function in two taxa and asked which enzyme a third taxon most likely uses. Experiment 1 and its follow-up, with college students, used triads involving amphibians, reptiles, and mammals (reptiles and mammals are most closely related evolutionarily) and plants, fungi, and animals (fungi are more closely related to animals than to plants). Experiment 2, with 10th graders, also included (...) triads involving mammals, birds, and snakes/crocodilians (birds and snakes/crocodilians are most closely related). Some subjects received cladograms (hierarchical diagrams) depicting the evolutionary relationships among the taxa. The effect of providing cladograms depended on students’ background in biology. The results illuminate students’ misconceptions concerning common taxa and constraints on their willingness to override faulty knowledge when given appropriate evolutionary evidence. Implications for introducing tree thinking into biology curricula are discussed. (shrink)

Discussions of the theory and practice of systematics and evolutionary biology have heretofore revolved around the views of philosophers of science. I reexamine these issues from the different perspective of the philosophy of history. Just as philosophers of history distinguish between chronicle (non-interpretive or non-explanatory writing) and narrative history (interpretive or explanatory writing), I distinguish between evolutionary chronicle (cladograms, broadly construed) and narrative evolutionary history. Systematics is the discipline which estimates the evolutionary chronicle. ¶ Explanations of the events described (...) in the evolutionary chronicle are not of the covering-law type described by philosophers of science, but rather of the how-possibly, continuous series, and integrating types described by philosophers of history. Pre-evolutionary explanations of states (in contrast to chroniclar events) are still widespread in "evolutionary" biology, however, because evolutionary chronicles are in general poorly known. To the extent that chronicles are known, the narrative evolutionary histories based on them are structured like conventional historical narratives, in that they treat their central subjects as ontological individuals. This conventional treatment is incorrect. The central subjects of evolutionary narratives are clades, branched entities which have some of the properties of individuals and some of the properties of classes. Our unconscious treatment of the subjects of evolutionary narratives as individuals has been the cause of erroneous notions of progress in evolution, and of views that taxa "develop" ontogenetically in ways analogous to individual organisms. We must rewrite our narrative evolutionary histories so that they properly represent the branching nature of evolution, and we must reframe our evolutionary philosophies so that they properly reflect the historical nature of our subject. (shrink)

Brackets and tables, circles and maps, 1554-1872 -- Early botanical networks and trees, 1766-1815 -- The first evolutionary tree, 1786-1820 -- Diverse and unusual trees of the early nineteenth century, 1817-1834 -- The rule of five, 1819-1854 -- Pre-Darwinian branching diagrams, 1828-1858 -- Evolution and the trees of Charles Darwin, 1837-1868 -- The trees of Ernst Haeckel, 1866-1905 -- Post-Darwinian nonconformists, 1868-1896 -- More late-nineteenth-century trees, 1874-1897 -- Trees of the early twentieth century, 1901-1930 -- The trees of Alfred Sherwood (...) Romer, 1933-1966 -- Additional trees of the mid-twentieth century, 1931-1943 -- The trees of William King Gregory, 1938-1951 -- Hints of new approaches, 1954-1969 -- Phenograms and cladograms, 1958-1966 -- Early molecular trees, 1962-1987 -- Notable trees of the past four decades, 1970-2010 -- Primeval branches and universal trees of life, 1997-2010. (shrink)

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)

Both written and graphic accounts of history can be biased by the perspective of the historian. O’Hara (Biol Philos 7:135–160, 1992) has demonstrated that this also applies to evolutionary history and its historians, and identified four narrative devices that introduce anthropocentricisms into accounts of phylogeny. In the current paper, I identify a fifth such narrative device, viz. the left–right ordering of the taxa at the tips of cladograms. I define two measures that make it possible to quantify the degree (...) of anthropocentricism of cladograms, the human attention score and human rightness score. I then carry out an analysis of the presence of the different distorting mechanisms in phylogenetic textbooks. I deliberately chose two textbooks that adopted a cladistic perspective, since their authors can be assumed to be more conscious about the aim of avoiding anthropocentricisms. Three of the narrative devices are thus absent from cladistic works. However, there is a weak tendency that the resolution of cladogram branches is biased in favour of Homo sapiens. Furthermore, the human perspective is clear and highly significant in the positioning of taxa along the left–right axis of cladograms. I discuss the reasons for and implications of these biased presentations. (shrink)

Chapter 4 asks how, to what extent, and why the worm can be used as a model organism for other organisms including humans. The answer lies partly in the notion of deep homology and connectivity among organisms. The notion of homology is illustrated in terms of both analogy and common descent using a worm cladogram. This chapter also introduces another theme that will be encountered in chapter 5 on types of reduction in biology and chapter 7 on schizophrenia. This theme (...) is the way in which biological knowledge in general is structured and emphasizes the importance of models in biology in contrast with physics, including parts and aspects of biological models such as mechanisms, pathways, networks, and circuits. These models are "exemplars" used as (interlevel) prototypes to organize information about other similar (overlapping) models, to which they are related more by biological analogical reasoning than by deductive elaboration. (shrink)

Short interspersed repetitive elements, or SINEs, are tRNA-derived retroposons that are dispersed throughout eukaryotic genomes and can be present in well over 104 total copies. The enormous volume of SINE amplifications per organism makes them important evolutionary agents for shaping the diversity of genomes, and the irreversible, independent nature of their insertion allows them to be used for diagnosing common ancestry among host taxa with extreme confidence. As such, they represent a powerful new tool for systematic biology that can be (...) strategically integrated with other conventional phylogenetic characters, most notably morphology and DNA sequences. This review covers the basic aspects of SINE evolution that are especially relevant to their use as systematic characters and describes the practical methods of characterizing SINEs for cladogram construction. It also discusses the limits of their systematic utility, clarifies some recently published misunderstandings, and illustrates the effective application of SINEs for vertebrate phylogenetics with results from selected case studies. BioEssays 22:148–160, 2000. ©2000 John Wiley & Sons, Inc. (shrink)

Despite the amount of work that has been produced on the subject over the years, the ‘transformation of cladistics’ is still a misunderstood episode in the history of comparative biology. Here, I analyze two outstanding, highly contrasting historiographic accounts on the matter, under the perspective of an influential dichotomy in the philosophy of science: the opposition between Scientific Realism and Empiricism. Placing special emphasis on the notion of ‘causal grounding’ of morphological characters in modern developmental biology’s theories, I arrive at (...) the conclusion that a ‘new transformation of cladistics’ is philosophically plausible. This ‘reformed’ understanding of ‘pattern cladistics’ entails retaining the interpretation of cladograms as ‘schemes of synapomorphies’, but in association to construing cladogram nodes as ‘developmental-genetic taxic homologies’, instead of ‘standard Darwinian ancestors’. The reinterpretation of pattern cladistics presented here additionally proposes to take Bas Van Fraassen’s ‘constructive empiricism’ as a philosophical stance that could properly support such analysis of developmental-genetic data for systematic purposes. The latter suggestion is justified through a reappraisal of previous ideas developed by prominent pattern cladists , which concerned a scientifically efficient ‘observable/non-observable distinction’ linked to the conceptual pair ‘ontogeny and phylogeny’. Finally, I argue that a robust articulation of Antirealist alternatives in systematics may provide a rational basis for its disciplinary separation from evolutionary biology, as well as for a critical reconsideration of the proper role of certain Scientific Realist positions, currently popular in comparative biology. (shrink)

In a recent paper,(1) palaeontologist Mike Benton claimed that our ability to reconstruct accurately the tree of Life may not have improved significantly over the last 100 years. This implies that the cladistic and molecular revolutions may have promulgated as much bad “black box” science as rigorous investigation. Benton's assessment was based on the extent to which cladograms (typically constructed with reference only to distributions of character states) convey the same narrative as the geochronological ages of fossil taxa (an (...) independent data set). Fossil record quality varies greatly between major clades, and the palaeontological dating “yardstick” may be more appropriate for some groups than others. BioEssays 24:203–207, 2002. © 2002 Wiley Periodicals, Inc.; DOI 10.1002/bies.10065. (shrink)

The dangers of character reification for cladistic inference are explored. The identification and analysis of characters always involves theory-laden abstraction—there is no theory-free “view from nowhere.” Given theory-ladenness, and given a real world with actual objects and processes, how can we separate robustly real biological characters from uncritically reified characters? One way to avoid reification is through the employment of objectivity criteria that give us good methods for identifying robust primary homology statements. I identify six such criteria and explore each (...) with examples. Ultimately, it is important to minimize character reification, because poor character analysis leads to dismal cladograms, even when proper phylogenetic analysis is employed. Given the deep and systemic problems associated with character reification, it is ironic that philosophers have focused almost entirely on phylogenetic analysis and neglected character analysis. (shrink)

Systematics based solely on structuralist principles is non-science because it is derived from first principles that are inconsistent in dealing with both synchronic and diachronic aspects of evolution, and its evolutionary models involve hidden causes, and unnameable and unobservable entities. Structuralist phylogenetics emulates axiomatic mathematics through emphasis on deduction, and “hypotheses” and “mapped trait changes” that are actually lemmas and theorems. Sister-group-only evolutionary trees have no caulistic element of scientific realism. This results in a degenerate systematics based on patterns of (...) fact or evidence being treated as so fundamental that all other data may be mapped to the cladogram, resulting in an apparently well-supported classification that is devoid of evolutionary theory. Structuralism in systematics is based on a non-ultrametric analysis of sister-group informative data that cannot detect or model a named taxon giving rise to a named taxon, resulting in classifications that do not reflect macroevolutionary changes unless they are sister lineages. Conservation efforts are negatively affected through epistemological extinction of scientific names. Evolutionary systematics is a viable alternative, involving both deduction and induction, hypothesis and theory, developing trees with both synchronic and diachronic dimensions often inferring nameable ancestral taxa, and resulting in classifications that advance evolutionary theory and explanations for particular groups. (shrink)