Biologists studying ecology and evolution use the term “population” in many different ways. Yet little philosophical analysis of the concept has been done, either by biologists or philosophers, in contrast to the voluminous literature on the concept of “species.” This is in spite of the fact that “population” is arguably a far more central concept in ecological and evolutionary studies than “species” is. The fact that such a central concept has been employed in so many different ways is potentially problematic (...) for the reason that inconsistent usages (especially when the usage has not been made explicit) might lead to false controversies in which disputants are simply talking past one another. However, the inconsistent usages are not the only, or even the most important reason to examine the concept. If any set of organisms is legitimately called a “population,” selection and drift processes become purely arbitrary, too. Moreover, key ecological variables, such as abundance and distribution, depend on a nonarbitrary way of identifying populations. I sketch the beginnings of a population concept, drawing inspiration from the Ghiselin-Hull individuality thesis, and show why some alternative approaches are nonstarters. (shrink)

E. O. Wilson (1974: 54) describes the problem that social organisms pose: “On what bases do we distinguish the extremely modified members of an invertebrate colony from the organs of a metazoan animal?” This framing of the issue has inspired many to look more closely at how groups of organisms form and behave as emergent individuals. The possible existence of “superorganisms” test our best intuitions about what can count and act as genuine biological individuals and how we should study them. (...) As we will discuss, colonies of certain organisms display many of the properties that we usually reserve only to individual organisms. Although there is good reason to believe that many social insects form genuine emergent biological individuals, the conclusion offered here is of a slightly different sort. I will argue that to understand some social insects' interactions and the emergent traits they give rise to, it may be helpful to shift our understanding from a community-level approach to an ecosystem-level approach. I will argue that viewing certain insect colonies (termites) as parts of ecosystems allows us to better understand some of the adaptations that have emerged from their evolution. (shrink)

Millstein (2009) 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; populations are constructs of biologists variably defined by contexts of inquiry.

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.

The metaphysical nature of homologies has been variously characterized as natural kind, individualist, and pluralist-pragmatic. In this essay, I aim to build on the work of proponents of a natural kinds ontology for homologies using Richard Boyd’s influential HPC account of natural kinds. I aim to advance this position by showing the unique fit of extending the HPC account to homologies, deflecting individualist critiques, as well as the pluralist-pragmatic alternative, showing that homologies have a determinate metaphysical character as kinds. As (...) an important extension of this position, I attempt to explain away how the mistaken metaphysics of the individualist, and derivatively the pluralist-pragmatic approach that contextually embraces it, can facilitate certain elements of biological practice. (shrink)

According to the species-as-individuals thesis(hereafter S-A-I), species are cohesive entities. Barker and Wilson recently pointed out that the type of cohesion exhibited by species is fundamentally different from that of organisms (paradigmatic individuals), suggesting that species are homeostatic property cluster kinds. In this article, I propose a shift in how to approach cohesion in the context of S-A-I: instead of analyzing the different types of cohesion and questioning whether species have them, I focus on the role played by cohesion in (...) the identity of individuals. This shift allows us to recognize why cohesion matters to S-A-I, as well as to reconceive the analogy between species and organisms (paradigmatic individuals), and also allows us to highlight the context sensitivity of both ‘‘cohesion’’ and ‘‘individuals.’’ From this perspective, I identify two problems in Barker and Wilson’s argumentation. Firstly, the authors fail to recognize that species are individuals even if they do not have the same type of cohesion that organisms have. Secondly, their argument relies on a misinterpretation of S-A-I. I conclude that species cohesion is still best framed as a feature of species individuality rather than a feature of species as homeostatic property cluster kinds. The arguments presented here contribute to the re-articulation and reevaluation of S-A-I in the face of contemporary discussions. (shrink)

Groups, individuals, and evolutionary restraints : the making of the contemporary debate over group selection Content Type Journal Article Pages 1-14 DOI 10.1007/s10539-011-9255-5 Authors Andrew Hamilton, Center for Biology and Society, School of Life Sciences, Arizona State University, Tempe, AZ 85287-4501 USA Christopher C. Dimond, Center for Biology and Society, School of Life Sciences, Arizona State University, Tempe, AZ 85287-4501 USA Journal Biology and Philosophy Online ISSN 1572-8404 Print ISSN 0169-3867.

I spell out and update the individuality thesis, that species are individuals, and not classes, sets, or kinds. I offer three complementary presentations of this thesis. First, as a way of resolving an inconsistent triad about natural kinds; second, as a phylogenetic systematics theoretical perspective; and, finally, as a novel recursive account of an evolved character. These approaches do different sorts of work, serving different interests. Presenting them together produces a taxonomy of the debates over the thesis, and isolates ways (...) it has been productive. This goes to the larger point of this paper: a defense of the individuality thesis in terms of its utility, and an update of it in light of recent theoretical developments and empirical work in biology. (shrink)

One of intuitions driving the acceptance of a neat structured tree of life is the assumption that organisms and the lineages they form have somewhat stable spatial and temporal boundaries. The phenomenon of symbiosis shows us that such ‘fixist’ assumptions does not correspond to how the natural world actually works. The implications of lateral gene transfer (LGT) have been discussed elsewhere; I wish to stress a related point. I will focus on lateral function transfer (LFT) and will argue, using examples (...) of what many would call ‘superorganisms’, that the emergence of symbiotic individuals revives the importance of functional and adaptationist thinking in how we conceptualize the lineages of biological individuals. The consequence of the argument is that, if we really want to hold onto tree of life thinking, we had better accept that new saplings appear and disappear all the time. (shrink)

Building upon a non-standard understanding of evolutionary process focusing on variation and persistence, I will argue that communities and ecosystems can evolve by natural selection as emergent individuals. Evolutionary biology has relied ever increasingly on the modeling of population dynamics. Most have taken for granted that we all agree on what is a population. Recent work has reexamined this perceived consensus. I will argue that there are good reasons to restrict the term “population” to collections of monophyletically related replicators and (...) interactors, which explains why many existing models in population biology exclude by definition many genuine evolving biological individuals such as communities and ecosystems. By studying a case of community evolution, we will see that it is variation that is important to evolutionary processes, not populations. Variation within a population is only one of many types of variation that can lead to evolution by natural selection. The upshot of focusing on variation is that cases of community and ecosystem adaptive change become tractable in evolutionary terms. I will show that complex emergent individuals such as communities and ecosystems cannot be fully accommodated by conventional population/reproduction models but can be accommodated by variation/persistence models. (shrink)

This paper aims to illustrate one of the primary goals of the philosophy of biology⎯namely, the examination of central concepts in biological theory and practice⎯through an analysis of the concepts of population and metapopulation in evolutionary biology and ecology. I will first provide a brief background for my analysis, followed by a characterization of my proposed concepts: the causal interactionist concepts of population and metapopulation. I will then illustrate how the concepts apply to six cases that differ in their population (...) structure; this analysis will also serve to flesh out and defend the concepts a bit more. Finally, I will respond to some possible questions that my analysis may have raised and then conclude briefly. (shrink)