Optimality Models and the Propensity Interpretation of Fitness

ROFFÉ, ARIEL; GINNOBILI, SANTIAGO

Sao Paulo

Congreso; International Society for History, Philosophy and Social Studies of Biology; 2017

74. International Society for History, Philosophy and Social Studies of Biology (ISHPSSB) & Brazillian Association of Philosophy and History of Biology (ABFHIB)

The aim of this presentation is to examine the nature of the relation between optimality models and the concept of fitness. More specifically, to scrutinize the role that the so-called "Propensity interpretation of fitness" ascribes to optimality models in evolutionary biology. According to this account, the concept of fitness can be thought of as a probabilistic one; the novelty comes, however, in the way that it proposes to interpret this mathematical concept. Indeed, it is not done frequentially (i.e. the probability of an event A is its relative frequency in an infinite number of experiments), as is usual in most applications of probability theory, but rather as a propensity (i.e. the probability of A is its propensity to take place). Propensities, as dispositions, explain relative frequencies in the long run, so they can be determined/operationalized/estimated through them, just as in the frequentist interpretation. The point is that these dispositional properties should also be operationalizable independently of frequencies, otherwise the propensity account would collapse, in practice, with the frequency one. In the context of fitness as a propensity, this idea translates to the thesis that fitness values can be determined independently of actual reproductive success, via optimality models. So far, proponents of the propensity account have not specified exactly how these intependent determinations actually work, but a plausible way is via the models' currency values. For example, many claim that acceptable currencies must be chosen as "proxies" or "substitutes" of fitness values. We will argue that, at least for an important subset of optimality models (those coming from Optimal foraging theory), currency values cannot be taken to be operationalizations of fitness values, and thus cannot be used as "proxies" for them. Additionally, we will hold that the relation between currencies (such as energetic efficiency) and fitness is empirical and not conceptual; that is, that it is also possible to connect a frequentist concept of fitness with ecological considerations through some empirical statement(s). Finally, we suggest that restrictions on acceptable currencies come from functional biology, not from evolutionary biology. We conclude that, if the propensity account cannot adequately capture all of these facts, then it loses some of its initial appeal.