Hierarchical expansions of the theory of natural selection exist in two distinct bodies of thought in evolutionary biology, the group selection and the species selection traditions. Both traditions share the point of view that the principles of natural selection apply at levels of biological organization above the level of the individual organism. This leads them both to considermultilevel selection situations, where selection is occurring simultaneously at more than one level. Impeding unification of the theoretical approaches of the multilevel selection traditions (...) are the different goals of investigators in the different subdisciplines and the different types of data potentially available for analysis. We identify two alternative approaches to multilevel situations, which we termmultilevel selection [1] andmultilevel selection [2]. Of interest in the former case are the effects of group membership onindividual fitnesses, and in the latter the tendencies for the groups themselves to go extinct or to found new groups (i.e., group fitnesses). We argue that: neither represents the entire multilevel selection process; both are aspects of any multilevel selection situation; and both are legitimate approaches, suitable for answering different questions. Using this formalism, we show that: multilevel selection [2] does not require emergent group properties in order to provide an explanatory mechanism of evolutionary change; multilevel selection [1] is usually more appropriate for neontological group selection studies; and species selection is most fruitfully considered from the point of view of multilevel selection [2]. Finally we argue that the effect hypothesis of macroevolution, requiring, in selection among species, both the absence of group effects on organismic fitness (multilevel selection [1]), and the direct determination of species fitnesses by those of organisms, is untestable with paleontological data. Furthermore, the conditions for the effect hypothesis to hold are extremely restrictive and unlikely to apply to the vast majority of situations encountered in nature. (shrink)

A number of recent discussions have argued that George Price's equationfor representing evolutionary change is a powerful and illuminatingtool, especially in the context of debates about multiple levels ofselection. Our paper dissects Price's equation in detail, and comparesit to another statistical tool: the calculation and comparison ofaverage fitnesses. The relations between Price's equation and equationsfor evolutionary change using average fitness are closer than issometimes supposed. The two approaches achieve a similar kind ofstatistical summary of one generation of change, and they (...) achieve thisvia a similar loss of information about the underlying fitnessstructure. (shrink)

This paper distinguishes and critiques several forms of pluralism about the levels of selection, and introduces a novel way of thinking about the biological properties and processes typically conceptualized in terms of distinct levels. In particular, "levels" should be thought of as being entwined or fused. Since the pluralism discussed is held by divergent theorists, the argument has implications for many positions in the debate over the units of selection. And since the key points on which the paper turns apply (...) beyond this specific issue, the paper may prove of general interest in thinking about the metaphysics of science. (shrink)

Darwinians are realists about the force of selection, but there has been surprisingly little discussion about what form this realism should take. Arguments about the units of selection in general and genic selectionism in particular reveal two realist assumptions: (1) for any selection process, there is a uniquely correct identification of the operative selective forces and the level at which each impinges; and (2) selective forces must satisfy the Pareto-style requirement of probabilistic causation. I argue that both assumptions are false; (...) we must temper realism about the force of selection and revise the way we think about probabilistic causation. (shrink)

We distinguish dynamical and statistical interpretations of evolutionary theory. We argue that only the statistical interpretation preserves the presumed relation between natural selection and drift. On these grounds we claim that the dynamical conception of evolutionary theory as a theory of forces is mistaken. Selection and drift are not forces. Nor do selection and drift explanations appeal to the (sub-population-level) causes of population level change. Instead they explain by appeal to the statistical structure of populations. We briefly discuss the implications (...) of the statistical interpretation of selection for various debates within the philosophy of biologythe `explananda of selection' debate and the `units of selection' debate. (shrink)

Traditionally a scientific theory is viewed as based on universal laws of nature that serve as axioms for logical deduction. In analyzing the logical structure of evolutionary biology, Elisabeth Lloyd argues that the semantic account is more appropriate and powerful. This book will be of interest to biologists and philosophers alike.

Once upon a time in evolutionary theory, everything happened for the best. Predators killed only the old or the sick. Pecking orders and other dominance hierarchies minimized wasteful conflict within the group. Male displays ensured that only the best and the fittest had mates. In the culmination of this tradition, Wynne-Edwards argued that many species have mechanisms that ensure groups do not over-exploit their resource base. The “central function” of territoriality in birds and other higher animals is “of limiting the (...) numbers of occupants per unit area of habitat”. Species with dominance hierarchies, species with lekking breeding systems, and species with communal breeding regulate their populations. These social mechanisms have population regulation as their “underlying primary function”. Wynne-Edwards argued that these mechanisms evolve through group selection. Populations without such mechanisms are apt to go extinct by eroding their own resource base. (shrink)

In many texts on evolution the reader will find a characteristic depiction of inheritance and evolution, one showing the generations of an evolving population linked only by a causal flow from genotype to genotype. On this view, the genotype of each organism in this population plays a dual role as both the motor of individual development and as the sole causal channel across the generations. This picture is known to be literally false. In many species, parents exert direct causal influence (...) on their offspring, and some of those influences cause the offspring to resemble the parent. For example, a butterfly that lays her eggs on the same plant host on which she hatched thereby exerts a causal influence on her offspring, and one apt to cause them to resemble her more than they would, had she chosen a plant of a different species. None of this is at all controversial, but it poses a puzzle. If the “Weissmanian” conception is literally false, why is it seen as a perspicacious representation of evolution? (shrink)

This paper evaluates and criticises the developmental systems conception of evolution and develops instead an extension of the gene's eye conception of evolution. We argue (i) Dawkin's attempt to segregate developmental and evolutionary issues about genes is unsatisfactory. On plausible views of development it is arbitrary to single out genes as the units of selection. (ii) The genotype does not carry information about the phenotype in any way that distinguishes the role of the genes in development from that other factors. (...) (iii) There is no simple and general causal criterion which distinguishes the role of genes in development and evolution. (iv) There is, however, an important sense in which genes but not every other developmental factor represent the phenotype. (v) The idea that genes represent features of the phenotype forces us to recognise that genes are not the only, or almost the only, replicators. Many mechanisms of replication are involved in both development and evolution. (vi) A conception of evolutionary history which recognises both genetic and non-genetic replicators, lineages of replicators and interactors has advantages over both the radical rejection of the replicator/interactor distinction and the conservative restriction of replication to genetic replication. (shrink)

The ontological dependence of one domain on another is compatible with the explanatory autonomy of the less basic domain. That autonomy results from the fact that the relationship between two domains can be very complex. In this paper I distinguish two different types of complexity, two ways the relationship between domains can fail to be transparent, both of which are relevant to evolutionary biology. Sometimes high level explanations preserve a certain type of causal or counterfactual information which would be lost (...) at the lower level; I argue that this is central to the proper understanding of the adaptationist program. Sometimes high level kinds are multiply realised by lower level kinds: I argue that this is central to the understanding of macroevolution. (shrink)

The authors demonstrate that unselfish behavior is in fact an important feature of both biological and human nature. Their book provides a panoramic view of altruism throughout the animal kingdom--from self-sacrificing parasites to the human capacity for selflessness--even as it explains the evolutionary sense of such behavior.

The Nature of Selection is a straightforward, self-contained introduction to philosophical and biological problems in evolutionary theory. It presents a powerful analysis of the evolutionary concepts of natural selection, fitness, and adaptation and clarifies controversial issues concerning altruism, group selection, and the idea that organisms are survival machines built for the good of the genes that inhabit them. "Sober's is the answering philosophical voice, the voice of a first-rate philosopher and a knowledgeable student of contemporary evolutionary theory. His book merits (...) broad attention among both communities. It should also inspire others to continue the conversation."-Philip Kitcher, Nature "Elliott Sober has made extraordinarily important contributions to our understanding of biological problems in evolutionary biology and causality. The Nature of Selection is a major contribution to understanding epistemological problems in evolutionary theory. I predict that it will have a long lasting place in the literature."-Richard C. Lewontin. (shrink)

We have two main objections to Kerr and Godfrey-Smith's (2002) meticulous analysis. First, they misunderstand the position we took in Unto Others – we do not claim that individual-level statements about the evolution of altruism are always unexplanatory and always fail to capture causal relationships. Second, Kerr and Godfrey-Smith characterize the individual and the multi-level perspectives in terms of different sets of parameters. In particular, they do not allow the multi-level perspective to use the individual fitness parameters i and i. (...) We don't see why the multi-level perspective prevents one from thinking in these terms. Kerr and Godfrey-Smith's argument that Uyenoyama and Feldman's (1980, 1992) definition of altruism belongs more to the individualist perspective than it does to the multi-level perspective is an artifact of their choice of parameters; the same point applies to their argument about the individualism inherent in the idea of Class I and Class II fitness structures. (shrink)

Several evolutionary biologists have used a parsimony argument to argue that the single gene is the unit of selection. Since all evolution by natural selection can be represented in terms of selection coefficients attaching to single genes, it is, they say, "more parsimonious" to think that all selection is selection for or against single genes. We examine the limitations of this genic point of view, and then relate our criticisms to a broader view of the role of causal concepts and (...) the dangers of reification in science. (shrink)

The use of informational terms is widespread in molecular and developmental biology. The usage dates back to Weismann. In both protein synthesis and in later development, genes are symbols, in that there is no necessary connection between their form (sequence) and their effects. The sequence of a gene has been determined, by past natural selection, because of the effects it produces. In biology, the use of informational terms implies intentionality, in that both the form of the signal, and the response (...) to it, have evolved by selection. Where an engineer sees design, a biologist sees natural selection. (shrink)

Inevitably, much of this reply will concern points on which I disagree with one or other of the commentators. I should start, therefore, by saying that I am delighted to find that their thinking is in many ways similar to my own, and that a serious attempt is under way to clarify the concept of information in biology.

Maynard Smith notes that he provides a natural history and not a philosophical analysis of the use of concepts of information in contemporary biology. Just a natural history, however rich, would do little to resolve the ongoing controversy about the role of these concepts in biology. None of the disputants deny that the biological use of these concepts is pervasive. The dispute is about whether these concepts—and the framework in which they are embedded—continue to be of explanatory value in contemporary (...) biology. Fortunately, Maynard Smith does much more than provide a natural history: his contribution is also a sustained attempt to justify many of the uses of information in biology. (shrink)

The group selection controversy is about whether natural selection ever operates at the level of groups, rather than at the level of individual organisms. Traditionally, group selection has been invoked to explain the existence of altruistic behaviour in nature. However, most contemporary evolutionary biologists are highly sceptical of the hypothesis of group selection, which they regard as biologically implausible and not needed to explain the evolution of altruism anyway. But in their recent book, Elliot Sober and David Sloan Wilson [1998] (...) argue that the widespread opposition to group selection is founded on conceptual confusion. The theories that have been propounded as alternatives to group selection are actually group selection in disguise, they maintain. I examine their arguments for this claim, and John Maynard Smith's arguments against it. I argue that Sober and Wilson arrive at a correct position by faulty reasoning. In the final section, I examine the issue of how to apply the principle of natural selection at different levels of the biological hierarchy, which underlies the dispute between Sober and Wilson and Maynard Smith. (shrink)

This paper compares two well-known arguments in the units of selection literature, one due to , the other due to . Both arguments concern the legitimacy of averaging fitness values across contexts and making inferences about the level of selection on that basis. The first three sections of the paper shows that the two arguments are incompatible if taken at face value, their apparent similarity notwithstanding. If we accept Sober and Lewontin's criterion for when averaging genic fitnesses across diploid genotypes (...) is illegitmate, we cannot accept Sober and Wilson's criterion for when averaging individual fitnesses across groups is illegitimate, and vice versa. The final section suggests a possible way of reconciling the two arguments, by invoking an ambiguity in the concept of genic selection. (shrink)

A number of recent biologists have used multi-level selection theory to help explain the major transitions in evolution. I argue that in doing so, they have shifted from a ‘synchronic’ to a ‘diachronic’ formulation of the levels of selection question. The implications of this shift in perspective are explored, in relation to an ambiguity in the meaning of multi-level selection. Though the ambiguity is well-known, it has never before been discussed in the context of the major transitions.

Two alternative statistical approaches to modelling multi-level selection in nature, both found in the contemporary biological literature, are contrasted. The simple covariance approach partitions the total selection differential on a phenotypic character into within-group and between-group components, and identifies the change due to group selection with the latter. The contextual approach partitions the total selection differential into different components, using multivariate regression analysis. The two approaches have different implications for the question of what constitutes group selection and what does not. (...) I argue that the contextual approach is theoretically preferable. This has important implications for a number of issues in the philosophical debate about the levels of selection. Introduction Group selection and the covariance formulation of selection The contextual approach A modification of the simple covariance approach Consequences: frameshifting and additivity 5.1 Frameshifting 5.2 Additivity Conclusion. (shrink)

The idea that clades might be units of selection, defended by a number of biologists and philosophers of biology, is critically examined. I argue that only entities which reproduce, i.e. leave offspring, can be units of selection, and that a necessary condition of reproduction is that the offspring entity be able, in principle, to outlive its parental entity. Given that clades are monophlyetic by definition, it follows that clades do not reproduce, so it makes no sense to talk about a (...) clade's fitness, so clade selection is impossible. Three possible responses to this argument are examined and found wanting. (shrink)

In their recent book, Elliott Sober and David Wilson (1998) argue that evolutionary biologists have wrongly regarded kinship as the exclusive means by which altruistic behavior can evolve, at the expense of other mechanisms. I argue that Sober and Wilson overlook certain genetical considerations which suggest that kinship is likely to be a more powerful means for generating complex altruistic adaptations than the alternative mechanisms they propose.

Recent years have seen a renewed debate over the importance of groupselection, especially as it relates to the evolution of altruism. Onefeature of this debate has been disagreement over which kinds ofprocesses should be described in terms of selection at multiple levels,within and between groups. Adapting some earlier discussions, we presenta mathematical framework that can be used to explore the exactrelationships between evolutionary models that do, and those that donot, explicitly recognize biological groups as fitness-bearing entities.We show a fundamental set (...) of mathematical equivalences between these twokinds of models, one of which applies a form of multi-level selectiontheory and the other being a form of ``individualism.'' However, we alsoargue that each type of model can have heuristic advantages over theother. Indeed, it can be positively useful to engage in a kind ofback-and-forth switching between two different perspectives on theevolutionary role of groups. So the position we defend is a``gestalt-switching pluralism.''. (shrink)

The history and theoretical role of the concept of a ``replicator''is discussed, starting with Dawkins' and Hull's classic treatmentsand working forward. I argue that the replicator concept is still auseful one for evolutionary theory, but it should be revised insome ways. The most important revision is the recognition that notall processes of evolution by natural selection require thatsomething play the role of a replicator.

Maynard Smith is right that one of the most striking features of contemporary biology is the ever-increasing prominence of the concept of information, along with related concepts like representation, programming, and coding. Maynard Smith is also right that this is surely a phenomenon which philosophers of science should examine closely. We should try to understand exactly what sorts of theoretical commitment are made when biological systems are described in these terms, and what connection there is between semantic descriptions in biology (...) and in other domains. (shrink)

'...a challenging and useful book, both because it provokes a careful scrutiny of one's own basic ideas regarding evolutionary theory, and because it cuts across so many biological disciplines.' -The Quarterly Review of Biology 'In my view, this work exemplifies Theoretical Biology at its best...here is rampant speculation that is consistently based on cautious reasoning from the available data. Even more refreshing is the absence of sloganeering, grandstanding, and 'isms'.' -Biology and Philosophy 'Epigenetics is fundamental to understanding both development and (...) gene expression, and not surprisingly, evolutionary biologists have long been fascinated with its proper place in evolutionary theory...Enter Jablonka and Lamb, who provide a thoughtful review of the recent molecular literature and suggest a number of potential consequences.' -EvolutionSince first publication of this controversial book, much of the initial opposition to the ideas it contained has been replaced by a general, although often grudging, acceptance of them. Advances in knowledge, especially at the molecular level, have enhanced general awareness and interest in epigenetics and the evolution of systems that store and transmit information and put any of the authors' speculations on a more solid basis. This paperback edition contains a new Preface that sets out the major changes in the scientific world and in the authors' own thinking that have occurred since the book was published. A new Appendix provides a selected bibliography of the many books and articles about epigenetic inheritance and its role in evolution that have appeared since first publication. (shrink)

A historical and critical analysis of the concept of the gene that attempts to provide new perspectives and metaphors for the transformation of biology and its philosophy.