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.

Whatever we take “life” to mean, it must involve an attempt to describe the objective reality beyond scientists’ biases. Traditionally, this is thought to involve comparing our scientific categories to “natural kinds.” But this approach has been tainted with an implicit metaphysics, inherited from Aristotle, that does not fit biological reality. In particular, we must accept that biological categories will never be specifiable in terms of necessary and sufficient conditions or shared underlying physical structures that produce clean boundaries. Biology blurs (...) all lines and failure to embrace this unique feature has blocked attempts to reach consensus on the meaning of “life.” Thus, while the three classical accounts all fall short of offering a complete definition, their advocates fail to realize that they share the same view of life’s ultimate, functional hallmark: its uniquely rich adaptive capacity. I develop an account of life as adaptive capacity that sidesteps debates about the relative importance of specific mechanisms and the precise location of boundaries to bring the three classical accounts together under a shared conceptual framework. (shrink)

We review Evolution and the Levels of Selection by Samir Okasha. This important book provides a cohesive philosophical framework for understanding levels-of-selections problems in biology. Concerning evolutionary transitions, Okasha proposes that three stages characterize the shift from a lower level of selection to a higher one. We discuss the application of Okasha’s three-stage concept to the evolutionary transition from unicellularity to multicellularity in the volvocine green algae. Okasha’s concepts are a provocative step towards a more general understanding of the major (...) evolutionary transitions; however, the application of certain ideas to the volvocine model system is not straightforward. (shrink)

Determining whether a homoplastic trait is the result of convergence or parallelism is central to many of the most important contemporary discussions in biology and philosophy: the relation between evolution and development, the importance of constraints on variation, and the role of contingency in evolution. In this article, I show that two recent attempts to draw a black-or-white distinction between convergence and parallelism fail, albeit for different reasons. Nevertheless, I argue that we should not be afraid of gray areas: a (...) clarified version of S. J. Gould's earlier account, based on a separation of underlying developmental mechanisms from the realized trait, still represents a useful approach. (shrink)

What exactly is a genetic disease? For a phrase one hears on a daily basis, there has been surprisingly little analysis of the underlying concept. Medical doctors seem perfectly willing to admit that the etiology of disease is typically complex, with a great many factors interacting to bring about a given condition. On such a view, descriptions of diseases like cancer as geneticseem at best highly simplistic, and at worst philosophically indefensible. On the other hand, there is clearly some practical (...) value to be had by classifying diseases according to theirpredominant cause when this can be accomplished in a theoretically satisfactory manner. The question therefore becomes exactly how one should go about selecting a single causal factor among many to explain the presence of disease. When an attempt to defend such causal selection is made at all, the standard accounts offered (Koch's postulates, Hill's epidemiological criteria, manipulability) are all clearly inadequate. I propose, however, an epidemiological account of disease causation which walks the fine line between practical applicability and theoretical considerations of causal complexity and attempts to compromise between patient-centered and population-centered concepts of disease. The epidemiological account is the most basic framework consistent with our strongly held intuitions about the causal classification of disease, yet it avoids the difficulties encountered by its competitors. (shrink)

During the past hundred years or so, those scholars studying science have isolated themselves as much as possible from scientists as well as from workers in other disciplines who study science. The result of this effort is history of science, philosophy of science and sociology of science as separate disciplines. I argue in this paper that now is the time for these disciplinary boundaries to be lowered or at least made more permeable so that a unified discipline of Science Studies (...) might emerge. I discuss representative problems that stand in the way of such an integration. These problems may seem so formidable in the abstract that no one in their right mind would waste their time trying to bring about a unified field of Science Studies. However, those of us who limit ourselves to the study of the biological sciences have already formed a society in which workers from all disciplines can share their expertise -- the International Society for the History, Philosophy and Social Studies of Science. (shrink)

Philosophers have used the probabilistic relation of ’screening-off‘ to explicate concepts in the theories of causation and explanation. Brandon has used screening-off relations in an attempt to reconstruct an argument of Mayr and Gould that natural selection acts at the level of the organism. I argue that Brandon‘s reconstruction is unsuccessful.

Richard Lewontin's (1970) early work on the units of selection initiated the conceptual and theoretical investigations that have led to the hierarchical perspective on selection that has reached near consensus status today. This paper explores other aspects of his work, work on what he termed continuity and quasi-independence, that connect to contemporary explorations of modularity in development and evolution. I characterize such modules and argue that they are the true units of selection in that they are what evolution by natural (...) selection individuates, selects among, and transforms. (shrink)