One hotly debated philosophical question in the analysis of evolutionary theory concerns whether or not evolution and the various factors which constitute it (selection, drift, mutation, and so on) may profitably be considered as analogous to “forces” in the traditional, Newtonian sense. Several compelling arguments assert that the force picture is incoherent, due to the peculiar nature of genetic drift. I consider two of those arguments here—that drift lacks a predictable direction, and that drift is constitutive of evolutionary systems—and show that they both fail to demonstrate that a view of genetic drift as a force is untenable. I go on to diagnose the reasons for the stubborn persistence of this problem, considering two open philosophical issues and offering some preliminary arguments in support of the force metaphor.
KeywordsEvolutionary theory Genetic drift Force Causation Brownian motion
Special thanks to an audience at the APA Eastern Division Meeting, 2012, and particularly my commentators at that meeting, Lindley Darden and Lindsay Craig, without whom several of the best ideas here would be missing. Helpful comments were also provided at the APA by Tyler Curtain, Marc Lange, Massimo Pigliucci, and Beth Preston. Thanks as well to an audience at the 2012 PSA, especially Joshua Filler and Michael Goldsby, and an audience at the Notre Dame History and Philosophy of Science Colloquium, especially Anjan Chakravartty, Melinda Gormley, Christopher Hamlin, Pablo Ruiz de Olano, and Tom Stapleford. Finally, thanks to Edward Jurkowitz, Roberta Millstein, Grant Ramsey, and six anonymous referees for comments on various drafts of this paper. As usual, commentary should not be taken to imply endorsement, and all flaws are undoubtedly mine.
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