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Darwinism About Darwinism (Joeri Witteveen)

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Review of Darwinian Populations and Natural Selection by Peter Godfrey-Smith (Oxford Uni Press 2009)

“… devoted to fleshing out what makes a population Darwinian. This is done by scoring a given population on a variety of parameters, such as H, the fidelity of heredity, and V, the abundance of variation. So, instead of saying that a population must have heredity and variation—in the vein of the classical approach—the Darwinian populations framework ranks populations according to how much it possesses of each. The H and V parameters are familiar; they are derived from the classical summaries. The other parameters are less obvious. G-S discusses several important ones, but notes that these do not exhaust the options; other parameters may also be important in judging how Darwinian a population is. The new parameters that are discussed at some length are α, defined as the competitive interaction with respect to reproduction, C, for “continuity” or smoothness of the fitness landscape, and S, the dependence of reproductive differences on “intrinsic character.” The concept of continuity was introduced by Lewontin as the principle that “small changes in a characteristic must result in only small changes in ecological relations” (Lewontin 1978: 169). G-S extends this principle, and turns it into a parameter. One way to understand C is as the smoothness of the fitness landscape. The smoother the fitness landscape, the higher the value C takes for the population under consideration. C is determined by causes of both internal and external nature. Internal influences stem from the organism’s physiology and development. External influences on C are location, and interaction with others. G-S assigns the internal/external difference its own parameter, S, for “intrinsic character.” The higher a population’s score on C and S, the more Darwinian are the individuals it is composed of. C and S not only tell us something about what makes individuals more Darwinian, they also serve as a replacement for another vexed notion in evolutionary theory: drift. Selection is often contrasted with drift; change may be due to selection and/or drift. G-S suggests that the C and S parameters dissolve this dichotomy. What we take to be drift is in fact a combination of low values of C and/or S. So drift and selection are not two distinct factors, but are “distinctions along the gradients of S and C” (p. 61). After having discussed some of the parameters, G-S introduces a spatial framework of three-dimensional “Darwinian spaces” as a tool for further analysis. Along each of the three axes of a Darwinian space, we can put a parameter, on which a score from 0 to 1 can be obtained. For instance, if we put the H, C, and S parameters along the axes and start scoring populations, one that scores close to (0,0,0) is very marginal, and one that sits close to (1,1,1) is a paradigmatic Darwinian population. Scoring somewhere in between will make it a minimal Darwinian population.”

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