Laura Franklin-Hall | New York University (original) (raw)
Papers by Laura Franklin-Hall
Current Controversies in Philosophy of Science, 2019
Though biologists identify individuals as ‘male’ or ‘female’ across a broad range of animal speci... more Though biologists identify individuals as ‘male’ or ‘female’ across a broad range of animal species, the particular traits exhibited by males and females can vary tremendously. This diversity has led some to conclude that cross-animal sexes (males, or females, of whatever animal species) have “little or no explanatory power” (Dupré 1986: 447) and, thus, are not natural kinds in any traditional sense. This essay will explore considerations for and against this conclusion, ultimately arguing that the animal sexes, properly understood, are “historical explanatory kinds”: groupings that can be scientifically significant even while their members differ radically in their current properties and particular histories. Whether this makes them full-fledged natural kinds is a question I take up at the very end.
![Research paper thumbnail of The nootropic drug vinpocetine inhibits veratridine-induced [Ca2+]i increase in rat hippocampal CA1 pyramidal cells](https://attachments.academia-assets.com/42621652/thumbnails/1.jpg)
](Neurochemical research, 2001
The alkaloid derivative vinpocetine (14-ethoxycarbonyl-(3alpha,16alpha-ethyl)-14,15-eburnamine; C... more The alkaloid derivative vinpocetine (14-ethoxycarbonyl-(3alpha,16alpha-ethyl)-14,15-eburnamine; Cavinton) has a well known beneficial effect on brain function in hypoxic and ischemic conditions. While it increases CNS blood flow and improves cellular metabolism, relatively little is known about vinpocetine's underlying molecular mechanisms on the single cell level. Since apoptotic and necrotic cell damage is always preceded by an increase in [Ca2+]i, this study investigated the effect of vinpocetine on [Ca2+]i increases in acute brain slices. Sodium influx is an early event in the biochemical cascade that takes place during ischemia. The alkaloid veratridine can activate this Na+ influx, causing depolarization and increasing [Ca2+]i in the cells. Therefore, it can be used to simulate an ischemic attack in brain cells. Using a cooled CCD camera-based ratio imaging system and cell loading with fura 2/AM, the effect of vinpocetine on [Ca2+]i changes in single pyramidal neurons in t...
Considerable knowledge exists concerning the events mediating neuron death following a necrotic i... more Considerable knowledge exists concerning the events mediating neuron death following a necrotic insult; prompted by this, there have now been successful attempts to use gene therapy approaches to protect neurons from such necrotic injury. In many such studies, however, it is not clear what sequence of cellular events connects the overexpression of the transgene with the enhanced survival. We do so, exploring the effects of overexpressing the Glut-1 glucose transporter with an adenoviral vector in hippocampal cultures challenged with the excitotoxin kainic acid (KA). Such overexpression enhanced glucose transport, attenuated the decline in ATP concentrations, decreased the release of excitatory amino acid neurotransmitters, and decreased the total free cytosolic calcium load. Commensurate with these salutary effects, neuronal survival was enhanced with this gene therapy intervention. Thus, the neuroprotective effects of this particular gene therapy occurs within the known framework of the mechanisms of necrotic neuronal injury.
Neuroscience Letters, 1999
The determination of neurotoxicity in monolayer mixed cultures has traditionally necessitated the... more The determination of neurotoxicity in monolayer mixed cultures has traditionally necessitated the time consuming and subjective procedure of counting neurons. In this paper, we propose a modification of an immunohistochemical staining method with a neuron-specific antibody against MAP2, that allows for quantification of neuron number to be done using an enzyme-linked immunosorbent assay (ELISA) plate reader. This new procedure involves the use of the compound 2,3'-azino-bis(ethylbenzothiazoline-6-sulphonic acid) (ABTS) at the last stage of the staining procedure. We employed two neurotoxicity models (the excitotoxin kainic acid and the interactions between gp120, the glycoprotein of HIV, and the stress hormone corticosterone) to compare the results obtained with this new method and the old method of immunohistochemical staining followed by 3,3'-daminobenzidine (DAB) and the counting of neurons. The ABTS/ELISA method was found to be a fast, reliable and objective procedure for the quantification of neurotoxicity.
Journal of Neurochemistry, 2000
, the adrenal steroids secreted during stress, can compromise the ability of hippocampal neurons ... more , the adrenal steroids secreted during stress, can compromise the ability of hippocampal neurons to survive numerous necrotic insults. We have previously observed that GCs worsen the deleterious effects of gp120, the glycoprotein of the acquired immune deficiency syndrome virus, which can indirectly damage neurons and which is thought to play a role in the neuropathological features of human immunodeficiency virus infection. Specifically, GCs augment gp120-induced calcium mobilization, ATP depletion, decline in mitochondrial potential, and neurotoxicity in fetal monolayer cultures from a number of brain regions. In the present report, we demonstrate a similar gp120/GC synergy in adult hippocampal and cortical explants. We generated explants from rats that were either adrenalectomized, adrenally intact, or intact and treated with corticosterone to produce levels seen in response to major stressors. Metabolic rates in explants were then indirectly assessed with silicon microphysiometry, and cytosolic calcium concentrations were assessed with fura-2 fluorescent microscopy. We observed that basal levels of GCs tonically augment the disruptive effects of gp120 on metabolism in the CA1 cell field of the hippocampus and in the cortex. Moreover, raising GC concentrations into the stress range exacerbated the ability of gp120 to mobilize cytosolic calcium in a number of hippocampal cell fields. Finally, we observed that the synthetic GC prednisone had similarly exacerbating effects on gp120. Thus, GCs can worsen the deleterious effects of gp120 in a system that is more physiologically relevant than the fetal monolayer culture and in a region-specific manner.
Frontiers in Neuroscience, 2010
... How to Cite. Fekete, Á., Franklin, L., Ikemoto, T., Rózsa, B., Lendvai, B., Sylvester Vizi, E... more ... How to Cite. Fekete, Á., Franklin, L., Ikemoto, T., Rózsa, B., Lendvai, B., Sylvester Vizi, E. and Zelles, T. (2009), Mechanism of the persistent sodium current activator veratridine-evoked Ca 2+ elevation: implication for epilepsy. Journal of Neurochemistry, 111: 745756. ...
Proceedings of the Complex …, 2002
The concept of emergence plays a central role in the science(s) of complexity. Yet while its impo... more The concept of emergence plays a central role in the science(s) of complexity. Yet while its importance seems substantial, its clarity is not. Some researchers provide only vague definitions of emergence, or define it by example rather than by providing necessary and sufficient ...
Scientific Composition and Metaphysical Ground, 2016
This paper critiques the new mechanistic explanatory program on grounds that, even when applied t... more This paper critiques the new mechanistic explanatory program on grounds that, even when applied to the kinds of examples that it was originally designed to treat, it does not distinguish correct explanations from those that blunder. First, I offer a systematization of the explanatory account, one according to which explanations are mechanistic models that satisfy three desiderata: they must 1) represent causal relations, 2) describe the proper parts, and 3) depict the system at the right ‘level.’ Second, I argue that even the most developed attempts to fulfill these desiderata fall short by failing to appropriately constrain explanatorily apt mechanistic models.
Philosophical theories of explanation characterize the difference between correct and incorrect e... more Philosophical theories of explanation characterize the difference between correct and incorrect explanations. While remaining neutral as to which of these ‘first-order’ theories is right, this paper asks the ‘meta-explanatory’ question: is the difference between correct and incorrect explanation real, i.e., objective or mind-independent? After offering a framework for distinguishing realist from anti-realist views, I sketch three distinct paths to explanatory anti-realism.
Philosophical Studies
Both realist and anti-realist accounts of natural kinds possess prima facie virtues: realists can... more Both realist and anti-realist accounts of natural kinds possess prima facie virtues: realists can straightforwardly make sense of the apparent objectivity of the natural kinds, and anti-realists, their knowability. This paper formulates a properly anti-realist account designed to capture both merits. In particular, it recommends understanding natural kinds as 'categorical bottlenecks,' those categories that not only best serve us, with our idiosyncratic purposes and cognitive capacities, but also those of a wide range of alternative agents. By endorsing an ultimately subjective categorical principle, this view sidesteps the epistemological difficulties facing realist views. Yet partly in consequence of the ubiquity of robust causal processes in our universe, it nevertheless identifies natural kinds that are fairly, though not completely, objective.
Explanation in Biology
This paper uses the causal economy account of scientific explanation to give a causal-explanatory... more This paper uses the causal economy account of scientific explanation to give a causal-explanatory analysis of the distinction between causes and background conditions, applying the analysis to questions about ‘causal democracy’ in explanations of ontogeny.
British Journal for the Philosophy of Science
The interventionist account of causal explanation, in the version presented by Jim Woodward ([200... more The interventionist account of causal explanation, in the version presented by Jim Woodward ([2003]), has been recently claimed capable of buttressing the widely felt—though poorly understood—hunch that high-level, relatively abstract explanations, of the sort provided by sciences like biology, psychology and economics, are in some cases explanatorily optimal. It is the aim of this paper to show that this is mistaken. Due to a lack of effective constraints on the variables at the heart of the interventionist causal-explanatory scheme, as presently formulated it is either unable to prefer high-level explanations to low, or systematically overshoots, recommending explanations at so high of a level as to be virtually vacuous.
The Tree of Life has traditionally been understood to represent the history of species lineages. ... more The Tree of Life has traditionally been understood to represent the history of species lineages. However, recently researchers have suggested that it might be better interpreted as representing the history of cellular lineages, sometimes called the Tree of Cells. This paper examines and evaluates reasons offered against this cellular interpretation of the Tree of Life. It argues that some such reasons are bad reasons, based either on a false attribution of essentialism, on a misunderstanding of the problem of lineage identity, or on a limited view of scientific representation. I suggest that debate about the Tree of Cells and other successors to the traditional Tree of Life should be formulated in terms of the purposes these representations may serve. In pursuing this strategy, we see that the Tree of Cells cannot serve one purpose suggested for it: as an explanation for the hierarchical nature of taxonomy. We then explore whether, instead, the tree may play an important role in the dynamic modeling of evolution. As highly-integrated complex systems, cells may influence which lineage components can successfully transfer into them and how they change once integrated. Only if they do in fact have a substantial role to play in this process might the Tree of Cells have some claim to be the Tree of Life.
Philosophers of experiment have acknowledged that experiments are often more than mere hypothesis... more Philosophers of experiment have acknowledged that experiments are often more than mere hypothesis‐tests, once thought to be an experiment’s exclusive calling. Drawing on examples from contemporary biology, I make an additional amendment to our understanding of experiment by examining the way that `wide' instrumentation can, for reasons of efficiency, lead scientists away from traditional hypothesis‐directed methods of experimentation and towards exploratory methods.
Biology …, Jan 1, 2009
BACKGROUND: The concept of a tree of life is prevalent in the evolutionary literature. It stems f... more BACKGROUND: The concept of a tree of life is prevalent in the evolutionary literature. It stems from attempting to obtain a grand unified natural system that reflects a recurrent process of species and lineage splittings for all forms of life. Traditionally, the discipline of systematics operates in a similar hierarchy of bifurcating (sometimes multifurcating) categories. The assumption of a universal tree of life hinges upon the process of evolution being tree-like throughout all forms of life and all of biological time. In multicellular eukaryotes, the molecular mechanisms and species-level population genetics of variation do indeed mainly cause a tree-like structure over time. In prokaryotes, they do not. Prokaryotic evolution and the tree of life are two different things, and we need to treat them as such, rather than extrapolating from macroscopic life to prokaryotes. In the following we will consider this circumstance from philosophical, scientific, and epistemological perspectives, surmising that phylogeny opted for a single model as a holdover from the Modern Synthesis of evolution.
RESULTS: It was far easier to envision and defend the concept of a universal tree of life before we had data from genomes. But the belief that prokaryotes are related by such a tree has now become stronger than the data to support it. The monistic concept of a single universal tree of life appears, in the face of genome data, increasingly obsolete. This traditional model to describe evolution is no longer the most scientifically productive position to hold, because of the plurality of evolutionary patterns and mechanisms involved. Forcing a single bifurcating scheme onto prokaryotic evolution disregards the non-tree-like nature of natural variation among prokaryotes and accounts for only a minority of observations from genomes.
CONCLUSION: Prokaryotic evolution and the tree of life are two different things. Hence we will briefly set out alternative models to the tree of life to study their evolution. Ultimately, the plurality of evolutionary patterns and mechanisms involved, such as the discontinuity of the process of evolution across the prokaryote-eukaryote divide, summons forth a pluralistic approach to studying evolution.
Phil. Sci, Jan 1, 2007
Philosophical discussions of species have focused on multicellular, sexual animals and have often... more Philosophical discussions of species have focused on multicellular, sexual animals and have often neglected to consider unicellular organisms like bacteria. This article begins to fill this gap by considering what species concepts, if any, apply neatly to the bacterial world. First, I argue that the biological species concept cannot be applied to bacteria because of the variable rates of genetic transfer between populations, depending in part on which gene type is prioritized. Second, I present a critique of phylogenetic bacterial species, arguing that phylogenetic bacterial classification requires a questionable metaphysical commitment to the existence of essential genes. I conclude by considering how microbiologists have dealt with these biological complexities by using more pragmatic and not exclusively evolutionary accounts of species. I argue that this pragmatism is not borne of laziness but rather of the substantial conceptual problems in classifying bacteria based on any evolutionary standard.
Current Controversies in Philosophy of Science, 2019
Though biologists identify individuals as ‘male’ or ‘female’ across a broad range of animal speci... more Though biologists identify individuals as ‘male’ or ‘female’ across a broad range of animal species, the particular traits exhibited by males and females can vary tremendously. This diversity has led some to conclude that cross-animal sexes (males, or females, of whatever animal species) have “little or no explanatory power” (Dupré 1986: 447) and, thus, are not natural kinds in any traditional sense. This essay will explore considerations for and against this conclusion, ultimately arguing that the animal sexes, properly understood, are “historical explanatory kinds”: groupings that can be scientifically significant even while their members differ radically in their current properties and particular histories. Whether this makes them full-fledged natural kinds is a question I take up at the very end.
Neurochemical research, 2001
The alkaloid derivative vinpocetine (14-ethoxycarbonyl-(3alpha,16alpha-ethyl)-14,15-eburnamine; C... more The alkaloid derivative vinpocetine (14-ethoxycarbonyl-(3alpha,16alpha-ethyl)-14,15-eburnamine; Cavinton) has a well known beneficial effect on brain function in hypoxic and ischemic conditions. While it increases CNS blood flow and improves cellular metabolism, relatively little is known about vinpocetine's underlying molecular mechanisms on the single cell level. Since apoptotic and necrotic cell damage is always preceded by an increase in [Ca2+]i, this study investigated the effect of vinpocetine on [Ca2+]i increases in acute brain slices. Sodium influx is an early event in the biochemical cascade that takes place during ischemia. The alkaloid veratridine can activate this Na+ influx, causing depolarization and increasing [Ca2+]i in the cells. Therefore, it can be used to simulate an ischemic attack in brain cells. Using a cooled CCD camera-based ratio imaging system and cell loading with fura 2/AM, the effect of vinpocetine on [Ca2+]i changes in single pyramidal neurons in t...
Considerable knowledge exists concerning the events mediating neuron death following a necrotic i... more Considerable knowledge exists concerning the events mediating neuron death following a necrotic insult; prompted by this, there have now been successful attempts to use gene therapy approaches to protect neurons from such necrotic injury. In many such studies, however, it is not clear what sequence of cellular events connects the overexpression of the transgene with the enhanced survival. We do so, exploring the effects of overexpressing the Glut-1 glucose transporter with an adenoviral vector in hippocampal cultures challenged with the excitotoxin kainic acid (KA). Such overexpression enhanced glucose transport, attenuated the decline in ATP concentrations, decreased the release of excitatory amino acid neurotransmitters, and decreased the total free cytosolic calcium load. Commensurate with these salutary effects, neuronal survival was enhanced with this gene therapy intervention. Thus, the neuroprotective effects of this particular gene therapy occurs within the known framework of the mechanisms of necrotic neuronal injury.
Neuroscience Letters, 1999
The determination of neurotoxicity in monolayer mixed cultures has traditionally necessitated the... more The determination of neurotoxicity in monolayer mixed cultures has traditionally necessitated the time consuming and subjective procedure of counting neurons. In this paper, we propose a modification of an immunohistochemical staining method with a neuron-specific antibody against MAP2, that allows for quantification of neuron number to be done using an enzyme-linked immunosorbent assay (ELISA) plate reader. This new procedure involves the use of the compound 2,3'-azino-bis(ethylbenzothiazoline-6-sulphonic acid) (ABTS) at the last stage of the staining procedure. We employed two neurotoxicity models (the excitotoxin kainic acid and the interactions between gp120, the glycoprotein of HIV, and the stress hormone corticosterone) to compare the results obtained with this new method and the old method of immunohistochemical staining followed by 3,3'-daminobenzidine (DAB) and the counting of neurons. The ABTS/ELISA method was found to be a fast, reliable and objective procedure for the quantification of neurotoxicity.
Journal of Neurochemistry, 2000
, the adrenal steroids secreted during stress, can compromise the ability of hippocampal neurons ... more , the adrenal steroids secreted during stress, can compromise the ability of hippocampal neurons to survive numerous necrotic insults. We have previously observed that GCs worsen the deleterious effects of gp120, the glycoprotein of the acquired immune deficiency syndrome virus, which can indirectly damage neurons and which is thought to play a role in the neuropathological features of human immunodeficiency virus infection. Specifically, GCs augment gp120-induced calcium mobilization, ATP depletion, decline in mitochondrial potential, and neurotoxicity in fetal monolayer cultures from a number of brain regions. In the present report, we demonstrate a similar gp120/GC synergy in adult hippocampal and cortical explants. We generated explants from rats that were either adrenalectomized, adrenally intact, or intact and treated with corticosterone to produce levels seen in response to major stressors. Metabolic rates in explants were then indirectly assessed with silicon microphysiometry, and cytosolic calcium concentrations were assessed with fura-2 fluorescent microscopy. We observed that basal levels of GCs tonically augment the disruptive effects of gp120 on metabolism in the CA1 cell field of the hippocampus and in the cortex. Moreover, raising GC concentrations into the stress range exacerbated the ability of gp120 to mobilize cytosolic calcium in a number of hippocampal cell fields. Finally, we observed that the synthetic GC prednisone had similarly exacerbating effects on gp120. Thus, GCs can worsen the deleterious effects of gp120 in a system that is more physiologically relevant than the fetal monolayer culture and in a region-specific manner.
Frontiers in Neuroscience, 2010
... How to Cite. Fekete, Á., Franklin, L., Ikemoto, T., Rózsa, B., Lendvai, B., Sylvester Vizi, E... more ... How to Cite. Fekete, Á., Franklin, L., Ikemoto, T., Rózsa, B., Lendvai, B., Sylvester Vizi, E. and Zelles, T. (2009), Mechanism of the persistent sodium current activator veratridine-evoked Ca 2+ elevation: implication for epilepsy. Journal of Neurochemistry, 111: 745756. ...
Proceedings of the Complex …, 2002
The concept of emergence plays a central role in the science(s) of complexity. Yet while its impo... more The concept of emergence plays a central role in the science(s) of complexity. Yet while its importance seems substantial, its clarity is not. Some researchers provide only vague definitions of emergence, or define it by example rather than by providing necessary and sufficient ...
Scientific Composition and Metaphysical Ground, 2016
This paper critiques the new mechanistic explanatory program on grounds that, even when applied t... more This paper critiques the new mechanistic explanatory program on grounds that, even when applied to the kinds of examples that it was originally designed to treat, it does not distinguish correct explanations from those that blunder. First, I offer a systematization of the explanatory account, one according to which explanations are mechanistic models that satisfy three desiderata: they must 1) represent causal relations, 2) describe the proper parts, and 3) depict the system at the right ‘level.’ Second, I argue that even the most developed attempts to fulfill these desiderata fall short by failing to appropriately constrain explanatorily apt mechanistic models.
Philosophical theories of explanation characterize the difference between correct and incorrect e... more Philosophical theories of explanation characterize the difference between correct and incorrect explanations. While remaining neutral as to which of these ‘first-order’ theories is right, this paper asks the ‘meta-explanatory’ question: is the difference between correct and incorrect explanation real, i.e., objective or mind-independent? After offering a framework for distinguishing realist from anti-realist views, I sketch three distinct paths to explanatory anti-realism.
Philosophical Studies
Both realist and anti-realist accounts of natural kinds possess prima facie virtues: realists can... more Both realist and anti-realist accounts of natural kinds possess prima facie virtues: realists can straightforwardly make sense of the apparent objectivity of the natural kinds, and anti-realists, their knowability. This paper formulates a properly anti-realist account designed to capture both merits. In particular, it recommends understanding natural kinds as 'categorical bottlenecks,' those categories that not only best serve us, with our idiosyncratic purposes and cognitive capacities, but also those of a wide range of alternative agents. By endorsing an ultimately subjective categorical principle, this view sidesteps the epistemological difficulties facing realist views. Yet partly in consequence of the ubiquity of robust causal processes in our universe, it nevertheless identifies natural kinds that are fairly, though not completely, objective.
Explanation in Biology
This paper uses the causal economy account of scientific explanation to give a causal-explanatory... more This paper uses the causal economy account of scientific explanation to give a causal-explanatory analysis of the distinction between causes and background conditions, applying the analysis to questions about ‘causal democracy’ in explanations of ontogeny.
British Journal for the Philosophy of Science
The interventionist account of causal explanation, in the version presented by Jim Woodward ([200... more The interventionist account of causal explanation, in the version presented by Jim Woodward ([2003]), has been recently claimed capable of buttressing the widely felt—though poorly understood—hunch that high-level, relatively abstract explanations, of the sort provided by sciences like biology, psychology and economics, are in some cases explanatorily optimal. It is the aim of this paper to show that this is mistaken. Due to a lack of effective constraints on the variables at the heart of the interventionist causal-explanatory scheme, as presently formulated it is either unable to prefer high-level explanations to low, or systematically overshoots, recommending explanations at so high of a level as to be virtually vacuous.
The Tree of Life has traditionally been understood to represent the history of species lineages. ... more The Tree of Life has traditionally been understood to represent the history of species lineages. However, recently researchers have suggested that it might be better interpreted as representing the history of cellular lineages, sometimes called the Tree of Cells. This paper examines and evaluates reasons offered against this cellular interpretation of the Tree of Life. It argues that some such reasons are bad reasons, based either on a false attribution of essentialism, on a misunderstanding of the problem of lineage identity, or on a limited view of scientific representation. I suggest that debate about the Tree of Cells and other successors to the traditional Tree of Life should be formulated in terms of the purposes these representations may serve. In pursuing this strategy, we see that the Tree of Cells cannot serve one purpose suggested for it: as an explanation for the hierarchical nature of taxonomy. We then explore whether, instead, the tree may play an important role in the dynamic modeling of evolution. As highly-integrated complex systems, cells may influence which lineage components can successfully transfer into them and how they change once integrated. Only if they do in fact have a substantial role to play in this process might the Tree of Cells have some claim to be the Tree of Life.
Philosophers of experiment have acknowledged that experiments are often more than mere hypothesis... more Philosophers of experiment have acknowledged that experiments are often more than mere hypothesis‐tests, once thought to be an experiment’s exclusive calling. Drawing on examples from contemporary biology, I make an additional amendment to our understanding of experiment by examining the way that `wide' instrumentation can, for reasons of efficiency, lead scientists away from traditional hypothesis‐directed methods of experimentation and towards exploratory methods.
Biology …, Jan 1, 2009
BACKGROUND: The concept of a tree of life is prevalent in the evolutionary literature. It stems f... more BACKGROUND: The concept of a tree of life is prevalent in the evolutionary literature. It stems from attempting to obtain a grand unified natural system that reflects a recurrent process of species and lineage splittings for all forms of life. Traditionally, the discipline of systematics operates in a similar hierarchy of bifurcating (sometimes multifurcating) categories. The assumption of a universal tree of life hinges upon the process of evolution being tree-like throughout all forms of life and all of biological time. In multicellular eukaryotes, the molecular mechanisms and species-level population genetics of variation do indeed mainly cause a tree-like structure over time. In prokaryotes, they do not. Prokaryotic evolution and the tree of life are two different things, and we need to treat them as such, rather than extrapolating from macroscopic life to prokaryotes. In the following we will consider this circumstance from philosophical, scientific, and epistemological perspectives, surmising that phylogeny opted for a single model as a holdover from the Modern Synthesis of evolution.
RESULTS: It was far easier to envision and defend the concept of a universal tree of life before we had data from genomes. But the belief that prokaryotes are related by such a tree has now become stronger than the data to support it. The monistic concept of a single universal tree of life appears, in the face of genome data, increasingly obsolete. This traditional model to describe evolution is no longer the most scientifically productive position to hold, because of the plurality of evolutionary patterns and mechanisms involved. Forcing a single bifurcating scheme onto prokaryotic evolution disregards the non-tree-like nature of natural variation among prokaryotes and accounts for only a minority of observations from genomes.
CONCLUSION: Prokaryotic evolution and the tree of life are two different things. Hence we will briefly set out alternative models to the tree of life to study their evolution. Ultimately, the plurality of evolutionary patterns and mechanisms involved, such as the discontinuity of the process of evolution across the prokaryote-eukaryote divide, summons forth a pluralistic approach to studying evolution.
Phil. Sci, Jan 1, 2007
Philosophical discussions of species have focused on multicellular, sexual animals and have often... more Philosophical discussions of species have focused on multicellular, sexual animals and have often neglected to consider unicellular organisms like bacteria. This article begins to fill this gap by considering what species concepts, if any, apply neatly to the bacterial world. First, I argue that the biological species concept cannot be applied to bacteria because of the variable rates of genetic transfer between populations, depending in part on which gene type is prioritized. Second, I present a critique of phylogenetic bacterial species, arguing that phylogenetic bacterial classification requires a questionable metaphysical commitment to the existence of essential genes. I conclude by considering how microbiologists have dealt with these biological complexities by using more pragmatic and not exclusively evolutionary accounts of species. I argue that this pragmatism is not borne of laziness but rather of the substantial conceptual problems in classifying bacteria based on any evolutionary standard.