Most philosophical accounts of emergence are incompatible with reduction. Most scientists regard a system property as emergent relative to properties of the system's parts if it depends upon their mode of organization--a view consistent with reduction. Emergence can be analyzed as a failure of aggregativity--a state in which "the whole is nothing more than the sum of its parts." Aggregativity requires four conditions, giving tools for analyzing modes of organization. Differently met for different decompositions of the system, and in different (...) degrees, these conditions provide powerful evaluation criteria for choosing decompositions, and heuristics for detecting biases of vulgar reductionisms. This analysis of emergence is compatible with reduction. (shrink)

In both biology and the human sciences, social groups are sometimes treated as adaptive units whose organization cannot be reduced to individual interactions. This group-level view is opposed by a more individualistic one that treats social organization as a byproduct of self-interest. According to biologists, group-level adaptations can evolve only by a process of natural selection at the group level. Most biologists rejected group selection as an important evolutionary force during the 1960s and 1970s but a positive literature began to (...) grow during the 1970s and is rapidly expanding today. We review this recent literature and its implications for human evolutionary biology. We show that the rejection of group selection was based on a misplaced emphasis on genes as “replicators” which is in fact irrelevant to the question of whether groups can be like individuals in their functional organization. The fundamental question is whether social groups and other higher-level entities can be “vehicles” of selection. When this elementary fact is recognized, group selection emerges as an important force in nature and what seem to be competing theories, such as kin selection and reciprocity, reappear as special cases of group selection. The result is a unified theory of natural selection that operates on a nested hierarchy of units.The vehicle-based theory makes it clear that group selection is an important force to consider in human evolution. Humans can facultatively span the full range from self-interested individuals to “organs” of group-level “organisms.” Human behavior not only reflects the balance between levels of selection but it can also alter the balance through the construction of social structures that have the effect of reducing fitness differences within groups, concentrating natural selection (and functional organization) at the group level. These social structures and the cognitive abilities that produce them allow group selection to be important even among large groups of unrelated individuals. (shrink)

This paper surveys recent philosophy of biology. It aims to introduce outsiders to the field to the recent literature (which is reviewed in the footnotes) and the main recent debates. I concentrate on three of these: recent critiques of the replicator/vehicle distinction and its application to the idea of the gene as the unit of section; the recent defences of group selection and the idea that standard alternatives to group selection are in fact no more than a disguised form of (...) group selection; and recent ideas on the role of selection in evolution, especially the role of selection in structuring the large-scale history of life. The paper connects philosophy of biology to some more general problems in the philosophy of science, and concludes with a few suggestions about unfinished business. (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 evolutionary problem of the units of selection has elicited a good deal of conceptual work from philosophers. We review this work to determine where the issues now stand.

In an important article, Kim Sterelny and Philip Kitcher challenge the common assumption that for any biological phenomenon requiring a selectionist explanation, it is possible to identify a uniquely correct account of the relevant selection process. They argue that selection events can be modeled in any of a number of different, equally correct ways. They call their view ' Pluralism,' and explicitly connect it with various antirealist positions in the philosophy of science. I critically evaluate Sterelny and Kitcher's Pluralism along (...) with its attendant antirealist theses. In particular, I argue that there are serious problems with their pluralistic antirealism regarding units of selection. By correctly diagnosing these problems a more adequate position can be constructed. I defend such a position, which I designate Inclusive Hierarchical Monism, and show how it captures the important virtues of Sterelny and Kitcher's approach while avoiding its problems. (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)

What I suggest we can see in this brief overview of the literature is an extensive interpenetration on both sides of these debates between scientific, political, and social values. Important shifts in political and social values were of course occurring over the same period, some of them in parallel with, and perhaps even contributing to, these transitions I have been speaking of in evolutionary discourse. The developments that I think of as at least suggestive of possible parallels include the progressive (...) encroachment of public values into the private domain of post-World War II American life, the cold war, the rise of consumerism, and the flowering of what Christopher Lasch calls a “narcissistic individualism.”35 In popular language, the 1960s gave birth to the “me” generation. Perhaps the most tantalizing analogue is suggested by Barbara Ehrenreich's argument for the emergence of a new meaning of masculinity — an ideal of masculinity measured not by commitment, responsibility, or success as family provider, but precisely by the strength of a man's autonomy in the private sphere, his resistance to the demands of a hampering female.36 It is tempting to speculate about possible connections between changes in scientific discourse and developments in the social and political spheres, but such connections, however suggestive, would clearly have to be demonstrated.For now, however, I want to focus on another kind of change —a transformation not so much in the social or political sphere as in the scientific sphere. I make this turn, or return, in support of a more complex account of scientific change that incorporates reverberations within the scientific communty along with social and political changes.In the 1960s, all of biology was undergoing a major transformation in direct response to the dramatic successes of molecular biology. These successes seemed to completely vindicate the values on which the molecular revolution was premised — namely, simplicity and mechanism. Following the victory of Watson and Crick, and of others after them, the fever of that endeavor swept through biology leaving in its wake a new standard of science, and of scientific discourse — one predicated on clarity, simplicity, and analyzability; on the definition of legitimate questions as those capable of clear and unambiguous answers. Every biological discipline felt it — even evolutionary biology, which in some respects was at the furthest pole. Perhaps precisely because it seemed conceptually so remote, evolutionary biology may have felt it most of all. Lewontin inadvertently provides us with some direct support for this view. Indeed, he begins his introduction to Population Biology and Evolution with the following remarks: The twenty years since World War II have seen a vindication in biology of our faith in the Cartesian method as a way of doing science. Some of the most fundamental and interesting problems of biology have been solved or are very nearly solved by an analytic technique that is now loosely called “molecular biology.” But it is not specifically the “molecular” aspect of biology of the last twenty years that has led to its success. It is, rather, the analytic aspect, the belief that by breaking systems down into their component parts, by simplifying them or using simpler organisms, one can learn about more complex systems. As it happens, the problems that were attacked and are being attacked by this method lead to answers in terms of molecules and cell organelles.... There is a host of problems in biology, however, that has been much neglected in these twenty exciting years, because the answers to them cannot be meaningfully framed in molecular and cellular terms.37Lewontin is referring, of course, to problems in evolution. The remainder of his remarks is devoted to an argument for the applicability of the method, if not the content, of molecular biology to these problems. He writes, “It is not the case that molecular biology is Cartesian and analytic while population biology is holistic. Population biology is properly analytic and operates, within the framework of its own problems, by the process of simplification, analysis, and resynthesis.”38 With these remarks, he leads into the criticism of the “holists” who have “held up progress.”This new ethic of simplicity, clarity, and mechanism — embodying the very virtues lauded by Williams — was explicitly carried into evolutionary biology in the name of scientific progress. As it happened, the values implied also fit conveniently well with other values — each set of values providing crucial support for the other.However substantive the scientific gains may have been in some respects, the net effect of this ethic has also been a systematic “perceptual bias” — a bias with profound practical consequences for the entire program of methodological individualism in evolutionary biology, if not elsewhere as well. It may well be that the whole is equivalent to the reconstituted aggregate of its parts, if, in the process of aggregation or summation, all possible interactions among the parts are included. But if certain kinds of interactions are systematically excluded, our confidence in that program necessarily founders. My claim here is that such systematic exclusion does occur, and that it occurs on a number of different levels. To briefly review the interlocking kinds of “bias” that I see occurring in practice, I suggest the following schematic listing:On the most general level: The ethic of simplicity — the privileging of certain values, even certain methodologies, as having an a priori superior claim to scientific credibility.Only slightly less general, and crucially related, is the equation of “scientific” with “tractible”: Given the techniques of analysis available, the equation of science with what we can do inevitably leads to a systematic technical bias favoring simplicity. That is, because we don't know how to model complex dynamics, nonlinear interactions are systematically biased against because of the limitations of our technical know-how. The consequences of this equation of the scientific with the tractible are greatly compounded by the additional equation between what we can do and what is — that is, by our temptation to confuse tractibility with reality.Finally, and also closely related, a further kind of elision occurs even within the confines of tractibility. This kind of elision — taking the form almost of inferring tractibility from one's prior assumptions of what is real — is exemplified by the history of a mathematical ecology of mutualism. Even when mutualism can be introduced into the same technical machinery, it is still not pursued. The basic assumption is that competition is what is real, not because it is easier to model, but because it is what we expect. When the actual difficulties of modeling competition are then in turn suppressed, as in the Robert May story, what we have, given the temptation to equate the tractible with the real, is the possibility of a truly self-fulfilling prophecy. (shrink)

In a previous study, using experimental metapopulations of the flour beetle, Tribolium castaneum, we investigated phase III of Wright's shifting balance process (Wade and Griesemer 1998). We experimentally modeled migration of varying amounts from demes of high mean fitness into demes of lower mean fitness (as in Wright's characterization of phase III) as well as the reciprocal (the opposite of phase III). We estimated the meta-populational heritability for this level of selection by regression of offspring deme means on the weighted (...) parental deme means.Here we develop a Punnett Square representation of the inheritance of the group mean to place our empirical findings in a conceptual context similar to Mendelian inheritance of individual traits. The comparison of Punnett Squares for individual and group inheritance shows how the latter concept can be rigorously defined and extended despite the lack of explicitly formulated, simple Mendelian laws of inheritance at the group level. Whereas Wright's phase III combines both interdemic selection and meta-populational inheritance, our formulation separates the issue of meta-populational heritability from that of interdemic selection. We use this conceptual context to discuss the controversies over the levels of selection and the units of inheritance. (shrink)

The 'Evolution of Cooperation' addresses a simple yet age-old question; If living things evolve through competition, how can cooperation ever emerge? Despite the abundant evidence of cooperation all around us, there existed no purely naturalistic answer to this question until 1979, when Robert Axelrod famously ran a computer tournament featuring a standard game-theory exercise called The Prisoner's Dilemma. To everyone's surprise, the program that won the tournament, named Tit for Tat, was not only the simplest but the most "cooperative" entrant. (...) This unexpected victory proved that cooperation - one might even say altruism - is mathematically possible and therefore needs no hidden hand or divine agent to create and sustain it. A great roadblock to the understanding of all sorts of behavior was at last removed. The updated edition includes an extensive new chapter on cooperation in cancer cells and among terrorist organizations. (shrink)

Developing a definition of group selection, and applying that definition to the dispute in the social sciences between methodological holists and methodological individualists, are the two goals of this paper. The definition proposed distinguishes between changes in groups that are due to group selection and changes in groups that are artefacts of selection processes occurring at lower levels of organization. It also explains why the existence of group selection is not implied by the mere fact that fitness values of organisms (...) are sensitive to the composition of groups. And, lastly, the definition explains why group selection need not involve selection for altruism. Group selection is thereby seen as an evolutionary force which is objectively distinct from other evolutionary forces. Applying the distinction between group and individual selection to the holism/individualism dispute has the desirable result that the dispute is not decidable a priori. This way of looking at the dispute yields a conception of individualism which is untainted by atomism and a conception of holism which is unspoiled by hypostatis. (shrink)

A model is presented to account for the natural selection of what is termed reciprocally altruistic behavior. The model shows how selection can operate -against the cheater (non-reciprocator) in the system. Three instances of altruistic behavior are discussed, the evolution of which the model can explain: (1) behavior involved in cleaning symbioses; (2) warning cries in birds: and (3) human reciprocal altruism. Regarding human reciprocal altruism, it is shown that the details of the psychological system that regulates this altruism can (...) be explained by the model. Specifically, friendship,d islike, moralistic aggression, gratitude, sympathy, trust, suspicion, trustworthiness, aspects of guilt, and some forms of dishonesty and hypocrisy can be explained as important adaptations to regulate the altruistic system. Each individual human is seen as possessing altruistic and cheating tendencies, the expression of which is sensitive to developmental variables that were selected to set the tendencies at a balance appropriate to the local social and ecological environment. (shrink)

Human societies are based on cooperation among large numbers of genetically unrelated individuals. This behavior is puzzling from an evolutionary perspective. Because cooperators are..

The reductionistic vision of evolutionary theory, "the gene's eye view of evolution" is the dominant view among evolutionary biologists today. On this view, the gene is the only unit with sufficient stability to act as a unit of selection, with individuals and groups being more ephemeral units of function, but not of selection. This view is argued to be incorrect, on several grounds. The empirical and theoretical bases for the existence of higher-level units of selection are explored, and alternative analyses (...) discussed critically. The success of a multi-level selection theory demands the recognition and development of a multi-level genetics. The way to accomplish this is suggested. The genotype/phenotype distinction also requires further analysis to see how it applies at higher levels of organization. This analysis provides a way of defining genotype and phenotype for cultural evolution, and a treatment of the innate-acquired distinction which are both generalizeable to analyze problems of the nature and focus of scientific change. (shrink)

Two major clarifications have greatly abetted the understanding and fruitful expansion of the theory of natural selection in recent years: the acknowledgment that interactors, not replicators, constitute the causal unit of selection; and the recognition that interactors are Darwinian individuals, and that such individuals exist with potency at several levels of organization (genes, organisms, demes, and species in particular), thus engendering a rich hierarchical theory of selection in contrast with Darwin’s own emphasis on the organismic level. But a piece of (...) the argument has been missing, and individuals at levels distinct from organisms have been denied potency (although granted existence within the undeniable logic of the theory), because they do not achieve individuality with the same devices used by organisms and therefore seem weak by comparison. We show here that different features define Darwinian individuality across scales of size and time. In particular, species-individuals may develop few emergent features as direct adaptations. The interactor approach works with emergent fitnesses, not with emergent features; and species, as a consequence of their different mechanism for achieving individuality (reproductive exclusivity among subparts, that is, among organisms), express many effects from other levels. Organisms, by contrast, suppress upwardly cascading effects, because the organismic style of individuality (by functional integration of subparts) does not permit much competition or differential reproduction of parts from within. Species do not suppress the operation of lower levels; such effects therefore become available as exaptations conferring emergent fitness—a primary source of the different strength that species achieve as effective Darwinian individuals in evolution. (shrink)