Scientists use models to understand the natural world, and it is important not to conflate model and nature. As an illustration, we distinguish three different kinds of populations in studies of ecology and evolution: theoretical, laboratory, and natural populations, exemplified by the work of R.A. Fisher, Thomas Park, and David Lack, respectively. Biologists are rightly concerned with all three types of populations. We examine the interplay between these different kinds of populations, and their pertinent models, in three examples: the notion (...) of “effective” population size, the work of Thomas Park on /Tribolium/ populations, and model-based clustering algorithms such as /Structure/. Finally, we discuss ways to move safely between three distinct population types while avoiding confusing models and reality. (shrink)

I defend a radical interpretation of biological populations—what I call population pluralism—which holds that there are many ways that a particular grouping of individuals can be related such that the grouping satisfies the conditions necessary for those individuals to evolve together. More constraining accounts of biological populations face empirical counter-examples and conceptual difficulties. One of the most intuitive and frequently employed conditions, causal connectivity—itself beset with numerous difficulties—is best construed by considering the relevant causal relations as ‘thick’ causal concepts. I (...) argue that the fine-grained causal relations that could constitute membership in a biological population are huge in number and many are manifested by degree, and thus we can construe population membership as being defined by massively multidimensional constructs, the differences between which are largely arbitrary. I end by showing that positions in two recent debates in theoretical biology depend on a view of biological populations at odds with the pluralism defended here. (shrink)

Philosophers who study the problem of biological function often begin their deliberations by reflecting on the functions of parts of animals, or the behavior of animals. Applying theories of biological function to unconventional or borderline cases can help us to better evaluate and refine those theories. This is the case when we consider whether parts of transposable elements —bits of “selfish” DNA that move about within a host genome—have functions of their own, that is, whether the parts of TEs have (...) the function of helping the TE move about within the genome. Here I argue that whether or not the parts of TEs have functions depends crucially on whether collections of TEs form “populations,” by which I mean, here, a group of individuals of the same type that impact one another’s chances of persistence or multiplication, by impacting one another’s access to a shared resource. I think there is suggestive, but not conclusive, evidence that some TEs have functions of their own. Considering the problem of TE functionality, then, has value both for philosophy and for biology. (shrink)

Natural selection comes in degrees. Some biological traits are subjected to stronger selective force than others, selection on particular traits waxes and wanes over time, and some groups can only undergo an attenuated kind of selective process. This has downstream consequences for any notions that are standardly treated as binary but depend on natural selection. For instance, the proper function of a biological structure can be defined as what caused that structure to be retained by natural selection in the past. (...) We usually think of proper functions in binary terms: storing bile is a function of the gall bladder, but making stones is not. However, if functions arise through natural selection, and natural selection comes in degrees, then a binary approach to proper functions is in tension with the biological facts. In order to resolve this tension, we need to revise our standard accounts of proper function. In particular, we may have to seriously consider the possibility that functions themselves come in degrees, in spite of the ramifications this will have for the way we speak about functions and related concepts such as dysfunction, disease, and teleosemantic content. (shrink)

Biologists and philosophers have offered differing concepts of biological race. That is, they have offered different candidates for what a biological correlate of race might be; for example, races might be subspecies, clades, lineages, ecotypes, or genetic clusters. One thing that is striking about each of these proposals is that they all depend on a concept of population. Indeed, some authors have explicitly characterized races in terms of populations. However, including the concept of population into concepts of race raises three (...) puzzles, all having to do with time. In this paper, I extend the causal interactionist population concept (CIPC) by introducing some simple assumptions about how to understand populations through time. These assumptions help to shed light on the three puzzles, and in the process show that if we want to understand races in terms of populations, we will need to revise our concept(s) of race. (shrink)

This paper analyzes recent attempts to reject reproduction with lineage formation as a necessary condition for evolution by means of natural selection :560–570, 2008; Stud Hist Philos Sci Part C Stud Hist Philos Biol Biomed Sci 42:106–114, 2011; Bourrat in Biol Philos 29:517–538, 2014; Br J Philos Sci 66:883–903, 2015; Charbonneau in Philos Sci 81:727–740, 2014; Doolittle and Inkpen in Proc Natl Acad Sci 115:4006–4014, 2018). Building on the strengths of these attempts and avoiding their pitfalls, it is argued that (...) a robust formulation of evolution by natural selection without reproduction can be established. The main contribution of this paper is a reformulation of Lewontin’s three principles stating that minimal evolution by natural selection occurs when two conditions are met in a population: fitness-related variation and memory. Paradigmatic evolution by natural selection, which can generate adaptations, takes place when an additional condition is present, namely regeneration. (shrink)

I argue that the propensity interpretation of fitness, properly understood, not only solves the explanatory circularity problem and the mismatch problem, but can also withstand the Pandora’s box full of problems that have been thrown at it. Fitness is the propensity (i.e., probabilistic ability, based on heritable physical traits) for organisms or types of organisms to survive and reproduce in particular environments and in particular populations for a specified number of generations; if greater than one generation, “reproduction” includes descendants of (...) descendants. Fitness values can be described in terms of distributions of propensities to produce varying number of offspring and can be modeled for any number of generations using computer simulations, thus providing both predictive power and a means for comparing the fitness of different phenotypes. Fitness is a causal concept, most notably at the population level, where fitness differences are causally responsible for differences in reproductive success. Relative fitness is ultimately what matters for natural selection. (shrink)

While evolutionary thinking is increasingly becoming popular in fields of investigation outside the biological sciences, it remains unclear how helpful it is there and whether it actually yields good explanations of the phenomena under study. Here we examine the ontology of a recent approach to applying evolutionary thinking outside biology, the generalized Darwinism approach proposed by Geoffrey Hodgson and Thorbjørn Knudsen. We examine the ontology of populations in biology and in GD, and argue that biological evolutionary theory sets ontological criteria (...) that GD fails to meet. We suggest two options to revise the population concept in GD: reformulating the concept in terms of inheritance and reproduction such that it comes to pick out individuals similar to evolving populations, or trying to build an adequate population concept on a principle of differential retention instead of differential reproduction. 1 Introduction2 Generalized Darwinism2.1 What is generalized Darwinism?2.2 Darwinian principles3 The Ontology of Generalized Darwinism: What Are Populations?3.1 The population concept of generalized Darwinism3.2 The population concept in evolutionary theory4 Locating Evolving Systems in Generalized Darwinism5 Conclusion. (shrink)

This paper presents an account of the biological populations that can undergo paradigmatic natural selection. I argue for, and develop Peter Godfrey-Smith’s claim that reproductive competition is a core attribute of such populations. However, as Godfrey-Smith notes, it is not the only important attribute. I suggest what the missing element is, co-opting elements of Alan Templeton’s notion of exchangeability. The final framework is then compared to two recent discussions regarding biological populations proposed by Roberta Millstein and Jacob Stegenga.

For a population to undergo evolution by natural selection, it is assumed that the constituents of the population form parent-offspring lineages, that is, that they must reproduce. I challenge this assumption by dividing the notion of reproduction into two subprocesses, that is, multiplication and inheritance, that produce parent-offspring lineages between the parts of a population, and I show that their population-level roles, generation and memory, respectively, can be effected by processes that do not rely on such local-level lineages. I further (...) argue that these two population-level processes, not local parent-offspring lineages, are necessary conditions for a population to undergo Darwinian evolution. (shrink)

Contemporary biology has inherited two key assumptions from the Modern Synthesis about the nature of population lineages: sexual reproduction is the exemplar for how individuals in population lineages inherit traits from their parents, and random mating is the exemplar for reproductive interaction. While these assumptions have been extremely fruitful for a number of fields, such as population genetics and phylogenetics, they are increasingly unviable for studying the full diversity and evolution of life. I introduce the “mixture” account of population lineages (...) that escapes these assumptions by dissolving the Modern Synthesis’s sharp line separating reproduction and development and characterizing reproductive integration in population lineages by the ephemerality of isolated subgroups rather than random mating. The mixture account provides a single criterion for reproductive integration that accommodates both sexual and asexual reproduction, unifying their treatment under Kevin de Queiroz’s generalized lineage concept of species. The account also provides a new basis for empirically assessing the effect of random mating as an idealization on the empirical adequacy of population genetic models. (shrink)

We argue for a new conventionalism about many kinds of evolutionary groups, including clades, cohesive units, and populations. This rejects a consensus, which says that given any one of the many legitimate grouping concepts, only objective biological facts determine whether a collection is such a group. Surprisingly, being any one kind of evolutionary group typically depends on which of many incompatible values are taken by suppressed variables. This is a novel pluralism underlying most any one group concept, rather than a (...) familiar pluralism claiming many concepts are legitimate. Consequently, we must help biological facts determine grouphood, even when given a single grouping concept. (shrink)

The development of a biological notion of “population” over the first century of the theory of evolution has been commented upon by a number of historians and philosophers of biology. Somewhat less commonly discussed, however, is the parallel development of the statistical concept of a population over precisely the same period, in some cases driven by the same historical actors (such as Francis Galton and R. A. Fisher). We explore here these parallel developments, first from the perspective of a reconstruction (...) of the historical development of each concept, then with the aid of a digital analysis of a corpus of literature drawn from the journals Biometrika and Journal of Genetics, between 1900 and 1960. These twin analyses show both points of interesting overlap between these two historical trends as well as points of important divergence. The biological and statistical notions of “population” seem to be relatively clearly distinguishable over these six decades, in spite of the fact that a number of authors contributed clearly to both traditions. The complex interplay of continuity and discontinuity across these two notions of “population” makes them a particularly interesting case study of scientific conceptual change. (shrink)

Millstein argues against conceptual pluralism with respect to the definition of “population,” and proposes her own definition of the term. I challenge both Millstein’s negative arguments against conceptual pluralism and her positive proposal for a singular definition of population. The concept of population, I argue, does not refer to a natural kind; popula tions are constructs of biologists variably defined by contexts of inquiry.

In the recent philosophical literature, two questions have arisen concerning the status of natural selection: (1) Is it a population-level phenomenon, or is it an organism-level phenomenon? (2) Is it a causal process, or is it a purely statistical summary of lower-level processes? In an earlier work (Millstein, Br J Philos Sci, 57(4):627–653, 2006), I argue that natural selection should be understood as a population-level causal process, rather than a purely statistical population-level summation of lower-level processes or as an organism-level (...) causal process. In a 2009 essay entitled “Productivity, relevance, and natural selection,” Stuart Glennan argues in reply that natural selection is produced by causal pro- cesses operating at the level of individual organisms, but he maintains that there is no causal productivity at the population level. However, there are, he claims, many population-level properties that are causally relevant to the dynamics of evolution- ary processes. Glennan’s claims rely on a causal pluralism that holds that there are two types of causes: causal production and causal relevance. Without calling into question Glennan’s causal pluralism or his claims concerning the causal relevance of natural selection, I argue that natural selection does in fact exhibit causal production at the population level. It is true that natural selection does not fit with accounts of mechanisms that involve decomposition of wholes into parts, such as Glennan’s own. However, it does fit with causal production accounts that do not require decomposition, such as Salmon’s Mark Transmission account, given the extent to which populations act as interacting “objects” in the process of natural selection. (shrink)

I criticize some arguments against the causal interpretability of population genetics put forward by Denis Walsh ([2007], [2010]). In particular, I seek to undermine the contention that population genetics exhibits frame of reference relativity or subjectivity with respect to its formal representations. I also show that classical population genetics does not fall foul of some criteria for causal representation put forward by James Woodward ([2003]), although those criteria do undermine some causalist stances. 1 Introduction2 Modularity3 The Crucially Important Point4 The (...) Gillespie Case: Density-Dependent Selection5 Conclusion. (shrink)

In this paper, I identify two general positions with respect to the relationship between environment and natural selection. These positions consist in claiming that selective claims need and, respectively, need not be relativized to homogenous environments. I then show that adopting one or the other position makes a difference with respect to the way in which the effects of selection are to be measured in certain cases in which the focal population is distributed over heterogeneous environments. Moreover, I show that (...) these two positions lead to two different interpretations—the Pricean and contextualist ones—of a type of selection scenarios in which multiple groups varying in properties affect the change in the metapopulation mean of individual-level traits. Showing that these two interpretations stem from different attitudes towards environmental homogeneity allows me to argue: that, unlike the Pricean interpretation, the contextualist interpretation can only claim that drift or selection is responsible for the change in frequency of the focal trait in a given metapopulation if details about whether or not group formation is random are specified; that the traditional main objection against the Pricean interpretation—consisting in arguing that the latter takes certain side-effects of individual selection to be effects of group selection—is unconvincing. This leads me to suggest that the ongoing debate about which of the two interpretations is preferable should concentrate on different issues than previously thought. (shrink)

Selectionist evolutionary theory has often been faulted for not making novel predictions that are surprising, risky, and correct. I argue that it in fact exhibits the theoretical virtue of predictive capacity in addition to two other virtues: explanatory unification and model fitting. Two case studies show the predictive capacity of selectionist evolutionary theory: parallel evolutionary change in E. coli, and the origin of eukaryotic cells through endosymbiosis.

The origin and prevalence of transposable elements may best be understood as resulting from “selfish” evolutionary processes at the within-genome level, with relevant populations being all members of the same TE family or all potentially mobile DNAs in a species. But the maintenance of families of TEs as evolutionary drivers, if taken as a consequence of selection, might be better understood as a consequence of selection at the level of species or higher, with the relevant populations being species or ecosystems (...) varying in their possession of TEs. In 2015, Brunet and Doolittle made the case for legitimizing claims for an evolutionary role for TEs by recasting such claims as being about species selection. Here I further develop this “how possibly” argument. I note that with a forgivingly broad construal of evolution by natural selection we might come to appreciate many aspects of Life on earth as its products, and TEs as—possibly—contributors to the success of Life by selection at several levels of a biological hierarchy. Thinking broadly makes this proposition a testable Darwinian one. (shrink)

This article proposes two conditions to assess whether an entity at a level of description is a unit of selection qua interactor. These two conditions make it possible to (1) distinguish biologically relevant entities from arbitrary ones and (2) distinguish units that can _potentially_ enter a selection process from those that have already done so. I show that the classical approaches used in the literature on units and levels of selection do not fare well with respect to either or both (...) of these desiderata. (shrink)

This chapter provides an introduction to the study of the philosophical notions of mechanisms and causality in biology and economics. This chapter sets the stage for this volume, Mechanism and Causality in Biology and Economics, in three ways. First, it gives a broad review of the recent changes and current state of the study of mechanisms and causality in the philosophy of science. Second, consistent with a recent trend in the philosophy of science to focus on scientific practices, it in (...) turn implies the importance of studying the scientific methods employed by researchers. Finally, by way of providing an overview of each chapter in the volume, this chapter demonstrates that biology and economics are two fertile fields for the philosophy of science and shows how biological and economic mechanisms and causality can be synthesized. (shrink)

In this article, I consider the term “environment” in various claims and models by evolutionists and ecologists. I ask whether “environment” is amenable to a philosophical explication, in the same way some key terms of evolutionary theorizing such as “fitness,” “species,” or more recently “population” have been. I will claim that it cannot. In the first section, I propose a typology of theoretical terms, according to whether they are univocal or equivocal, and whether they have been the object of formal (...) or conceptual attempts of clarification. “Environment” will appear to be in a position similar to “population,” yet almost no extant attempt has been made to make sense of its meaning and reference. In the second section, I will present several theoretical claims or issues that refer to “environment” in apparently very diverse ways, but always supposing a contrastive term, which is not always the same. The third section directly considers models in evolution and in ecology, and asks “where” in them is the environment term. The fourth section proposes that “environment” refers to a distinction between a varying and an invariant term, but shows that this does not exhaust its meaning, which requires making more conceptual differences. Then, I take on the suggestion that there might be two “environment” terms, one in ecology and one in evolution, but show that is not the case. Finally I center on the specific notion of “complex environment,” which is the object of several research programs, and propose a typology of “complex environments” across theories. (shrink)

Philosophers are approaching a consensus that biological individuality, including evolutionary individuality, comes in degrees. Graded evolutionary individuality presents a puzzle when juxtaposed with another widely embraced view: that evolutionary individuality follows from being a selectable member of a Darwinian population. Population membership is, on the orthodox view, a bivalent condition, so how can members of Darwinian populations vary in their degree of individuality? This article offers a solution to the puzzle, by locating difference in degree of evolutionary individuality at the (...) level of population lineages, some of which are more Darwinian than others. In doing so, it sheds light on graded individuality in overlapping and nested population lineages, such as those that arise in multilevel selection and symbiotic collectives. (shrink)

The project of this paper is to understand what a phylogenetic tree represents and to discuss some of the implications that this has for the practice of systematics. At least the first part of this task, if not both parts, might appear trivial—or perhaps better suited for a single page in a textbook rather than a scholarly research paper. But this would be a mistake. While the task of interpreting phylogenetic trees is often treated in a trivial way, their interpretation (...) is tied to foundational conceptual questions at the heart of systematics—questions whose answers are hotly disputed. I have previously argued that widely shared ideas about the meaning and interpretation of phylogenetic trees are inconsistent with species concepts other than some genealogical version of a phylogenetic species concept (Velasco 2008). Here I rely on a similar approach and concentrate on the implications of the necessary conditions underlying the inferences that we make using phylogenetic trees. I argue that common practices for the interpretation and use of trees are in conflict and that unacceptable principles about species as units of phylogeny must be given up. According to the view that I will develop, all phylogenetic trees depict the history of populations. The branches on trees represent collections of population lineages through time and the splits represent population lineage splits. This is true regardless of whether the tips of the trees are themselves populations, or are species or higher taxa. Although this conclusion might be paired naturally with a view that species must be monophyletic groups, this population-centric view of trees is independent of that view of species. If we still want to have species that are paraphyletic groups of populations, this is permissible as long as we also do not treat species as the units of phylogeny. This population-centric view opposes a species-centric view of phylogeny and might be called a “rank-free” approach since it entails that we do not need to determine which groups are species (which is partly a ranking question) in order to build a tree. This conclusion and the argument for it are meant to be consistent with, but not require, acceptance of the conclusions of Velasco (2008) regarding species. (shrink)

In “‘Population’ is Not a Natural Kind of Kinds,” Jacob Stegenga argues against the claim that the concept of “population” is a natural kind and in favor of conceptual pluralism, ostensibly in response to two papers of mine (Millstein 2009, 2010). Pluralism is often an attractive position in the philosophy of science. It certainly is a live possibility for the concept of population in ecology and evolutionary biology, and I welcome the opportunity to discuss the topic further. However, I argue (...) that the case for conceptual pluralism has not yet been made. In what follows, I first clarify the issues at stake before taking up the topic of conceptual pluralism and responding to Stegenga’s criticisms of the causal interactionist population concept. (shrink)

Millikan’s (1984. Language, Thought, and Other Biological Categories: New Foundations for Realism. MIT Press) selected effects theory of functions states that functions are effects for which the ancestors of a trait were selected for. As the function is an effect a thing’s ancestors produced, only things that are reproductions in some sense can have functions. Against this reproduction requirement, Garson (2019. What Biological Functions Are and Why They Matter. Cambridge University Press) argues that not only processes of differential reproduction but (...) also processes of differential persistence can lead to new functions. Since such “persistence functions” have the same explanatory power as traditional selected effects functions, selected effects theorists should include them in their theory. In this paper, I will defend Millikan’s theory against this argument. I will show that the proponents of the generalized theory have yet to provide a working notion of populations that avoids a liberality problem. Further, I will argue that persistence functions are at best a marginal case of functions due to their restricted explanatory power. (shrink)

This year’s topic is “Genomics and Philosophy of Race.” Different researchers might work on distinct subsets of the six thematic clusters below, which are neither mutually exclusive nor collectively exhaustive: (1) Concepts of ‘Race’; (2) Mathematical Modeling of Human History and Population Structure; (3) Data and Technologies of Human Genomics; (4) Biological Reality of Race; (5) Racialized Selves in a Global Context; (6) Pragmatic Consequences of ‘Race Talk’ among Biologists.

Darwinian evolution is a population-level phenomenon. This paper deals with a structural population concept within the framework of generalized Darwinism, resp. within a generalized theory of evolution. According to some skeptical authors, GD is in need of a valid population concept in order to become a practicable research program. Populations are crucial and basic elements of any evolutionary explanation—biological or cultural—and have to be defined as clearly as possible. I suggest the “causal interactionist population concept”, by R. Millstein for this (...) purpose, and I will try to embed the approach into a generalized evolutionary perspective by mathematically formalizing its key definitions. Using graph-theory, populations as described in the CIPC can serve as proper clusters of evolutionary classification based on the rates of interactions between their elements. I will introduce the concept of a cohesion index as a measurement of possible population candidates within a distribution of elements. The strength of this approach lies in its applicability and interactions are relatively easy to observe. Furthermore, problems of clustering tokens via typicality, e.g. their similarity in intrinsic key characteristics, can be avoided, because CIPC is a external approach. However, some formal problems and conceptual ambiguities occur within a simple version of this CI, which will be addressed in this paper as well as some possible applications. (shrink)

There is surprisingly little philosophical work on conceptually spelling out the difference between the traits on which natural selection may be said to act (e.g. “having a high running speed”) and mere circumstantial traits (e.g. “happening to be in the path of a forest fire”). I label this issue the “selectable traits problem” and, in this paper, I propose a solution for it. I first show that, contrary to our first intuition, simply equating selectable traits with heritable ones is not (...) an adequate solution. I then go on to argue that two recent philosophical solutions to this problem—due to Peter Godfrey-Smith and Pierrick Bourrat—are unconvincing because they cannot accommodate frequency-dependent selection. The way out of this difficulty is, I argue, to accept that extrinsic properties dependent on relations between intrinsic properties of the population members should also count as selectable traits. I then show that my proposal is legitimized by more than the simple accommodation of frequency-dependent selection. (shrink)

Informed by his experiences as a hunter, forester, wildlife manager, ecologist, conservationist, and professor, Aldo Leopold developed a view he called the land ethic. In a classic essay, published posthumously in A Sand County Almanac, Leopold advocated for an expansion of our ethical obligations beyond the purely human to include what he variously termed the “land community” or the “biotic community”—communities of interdependent humans, nonhuman animals, plants, soils, and waters, understood collectively. This philosophy has been extremely influential in environmental ethics (...) as well as conservation biology and related fields. Using an approach grounded in environmental ethics and the history and philosophy of science, Roberta L. Millstein reexamines Leopold’s land ethic in light of contemporary ecology. Despite the enormous influence of the land ethic, it has sometimes been dismissed as either empirically out of date or ethically flawed. Millstein argues that these dismissals are based on problematic readings of Leopold’s ideas. In this book, she provides new interpretations of the central concepts underlying the land ethic: interdependence, land community, and land health. She also offers a fresh take on of his argument for extending our ethics to include land communities as well as Leopold-inspired guidelines for how the land ethic can steer conservation and restoration policy. (shrink)

This is a book review/critical review of Jackson and Depew's _Darwinism, Democracy, and Race: American Anthropology and Evolutionary Biology in the Twentieth Century_.