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Chance and Natural Selection John Beatty Philosophy of Science Vol 51 No 2 Jun 1984 pp 183 211 Stable URL http links jstor org sici sici 0031 8248 28198406 2951 3A2 3C183 3ACANS 3E2 0 CO 3B2 C Philosophy of Science is currently published by The University of Chicago Press Your use of the JSTOR archive indicates your acceptance of JSTOR s Terms and Conditions of Use available at http www jstor org about terms html JSTOR s Terms and Conditions of Use provides in part that unless you have obtained prior permission you may not download an entire issue of a journal or multiple copies of articles and you may use content in the JSTOR archive only for your personal non commercial use Please contact the publisher regarding any further use of this work Publisher contact information may be obtained at http www jstor org journals ucpress html Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printed page of such transmission The JSTOR Archive is a trusted digital repository providing for long term preservation and access to leading academic journals and scholarly literature from around the world The Archive is supported by libraries scholarly societies publishers and foundations It is an initiative of JSTOR a not for profit organization with a mission to help the scholarly community take advantage of advances in technology For more information regarding JSTOR please contact support jstor org http www jstor org Sun Aug 19 01 27 28 2007 Philosophy of Science June 1984 CHANCE AND NATURAL SELECTION JOHN BEATTY Department of Philosophy Arizona State Universitj Among the liveliest disputes in evolutionary biology today are disputes concerning the role of chance in evolution more specifically disputes concerning the relative evolutionary importance of natural selection vs so called random drift The following discussion is an attempt to sort out some of the broad issues involved in those disputes In the first half of this paper I try to explain the differences between evolution by natural selection and evolution by random drift On some common construals of natural selection those two modes of evolution are completely indistinguishable Even on a proper construal of natural selection it is difficult to distinguish between the improbable results of natural selection and evolution by random drift In the second half of this paper I discuss the variety of positions taken by evolutionists with respect to the evolutionary importance of random drift vs natural selection I will then consider the variety of issues in question in terms of a conceptual distinction often used to describe the rise of probabilistic thinking in the sciences I will argue in particular that what is going on here is not as might appear at first sight just another dispute about the desirability of stochastic vs deterministic theories Modem evolutionists do not argue so much about whether evolution is stochastic but about how stochastic it is Received June 1983 revised February 1984 This article was written during the academic year 1982 1983 while I was a fellow at the Center for Interdisciplinary Research at the University of Bielefeld in Bielefeld West Germany I was part of a group research project organized by Lorenz Kriiger which studied the rise and role of probabilistic thinking in the sciences since 1800 I am very grateful to the staff of the Center the faculty of the University of Bielefeld and of course my fellow probabilists for their thoughts and for their friendship Robert Brandon Lorenz Kriiger Elliott Sober Kenneth Waters and the referees of Philosoplzy of Science all helped me to clarify the issues discussed here The residual unclarity distinguishes my contributions from theirs Some of the residual unclarity must be attributed to Jonathan Hodge s and Alexander Rosenberg s critiques of the notion of fitness used here Their thoughtful critiques have I must admit left me a bit confused about my position Philosophy of Science 51 1984 pp 183 21 1 Copyright 0 1984 by the Philosophy of Science Association 184 JOHN BEATTY 1 Introduction Charles Darwin s account of organic form appealed to chance in a way that did not settle well with his critics As Darwin unhappily reported the opinion of the great scientist philosopher John Herschel I have heard by a round about channel that Herschel says my book is the law of higgledy piggledy What exactly this means I do not know but it is evidently very contemptuous Darwin to Lyell Dec 12 1859 in F Darwin 1887 Vol 2 p 37 In time though Darwin was praised rather than scorned for his appeal to chance For instance looking back at the turn of the century another great scientist philosopher C S Peirce assessed Darwin s contribution in this regard more favorably The Origin of Species was published toward the end of the year 1859 The preceding years since 1846 had been one of the most productive seasons or if extended so as to cover the great book we are considering the most productive period of equal length in the entire history of science from its beginnings until now For the idea that chance begets order was at that time put into its clearest light Peirce 1893 p 183 Since the turn of the century however and especially since the thirties evolutionists havefurther appealed to chance in ways that Darwin himself might contemptuously have regarded as higgledy piggledy views of nature Indeed proponents of one such appeal have coined the term nonDarwinian evolution to distance their views from his Actually the new appeals to chance have been matters of considerable dispute And today those disputes are among the liveliest in the already lively field of evolutionary biology The following discussion is an attempt to sort out some of the broad issues involved in these disputes The most general question at issue concerns the relative evolutionary importance of random drift vs natural selection But what does that mean In the first half of this paper Sections 2 3 I will try to make sense of that question That will involve explaining the sense in which evolution by random drift is properly speaking an alternativewto evolution by natural selection Darwin did not conceive of chance as anything like an alternative to natural selection but rather as complimentary to natural selection Modern evolutionists on the other hand recognize alternative as well as complimentary roles of chance and natural selection And yet on some common construals of natural

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