Multiple Realization and Evolutionary Dynamics: A Fitness-Based Account

ABSTRACT

Multiple realization occurs when a natural kind is variably realized at more basic levels and the common physical structure of the realizers is not essential for supporting nomological statements. It has been suggested that this phenomenon may be an outcome of natural selection acting over multiple realizers that perform an adaptive function. In this paper, we make the following contributions. First, we present a revision of this model, characterized by stricter equilibrium conditions and superior explanatory power. Second, we present a typology of multiple realization that provides a plausible account of the differences between across- and within-species multiple realization. Third, we perform a formal analysis of the dynamics of multiple realization that sheds light on the differences between multiple realization at different levels of organization.

KEYWORDS:

• multiple realization
• natural selection
• evolutionary dynamics

Disclosure Statement

No potential conflict of interest was reported by the authors.

Notes

1 According to the functional-cum-selective account, selection does not entail multiple realization. However, this account is committed to the presence of selection in instances of multiple realization. As David Papineau [2009] suggests, an argument against this account would be to identify a case of multiple realization that does not involve traits that are subject to either selection or intelligent design.

2 In finite populations, the condition of equal fitness does not apply strictly. Relatively unfit traits can persist over evolutionary time by genetic drift.

3 One could think of realizers that are linked by complementarity rather than substitution, as in Aizawa [2013]. We leave this extension of our typology for further research.

4 This does not rule out that multiple traits or behaviours in different niches could have the same fitness by chance.

5 We are agnostic as to whether evolutionary thinking can be applied to anthropology. We claim, nevertheless, that, if this were the case, multiply realized generalizations must satisfy the equal fitness condition.

6 The authors are grateful for comments to Eleonora Cresto, David Papineau, and Dan Sperber.