Abstract:

The new foundation for the propensity interpretation of fitness (PIF), developed by Pence and Ramsey, describes fitness as a probability distribution that encompasses all possible daughter populations to which the organism may give rise, including daughter populations in which traits might change and the possible environments that members of the daughter populations might encounter. This long-term definition of fitness is general enough to avoid counterexamples faced by previous mathematical conceptions of PIF. However, there seem to be downsides to its generality: the ecological role of fitness involves describing the degree of adaptedness between an organism and the specific environment it inhabits. When all possible changes in traits and all possible environments that a daughter population may encounter are included in the concept, it becomes difficult to see how fitness can fulfill this role. In this paper, we argue that this is a feature of Pence and Ramsey’s view rather than a bug: long-term fitness accommodates evolvability considerations, which concern the role that variation plays in evolutionary processes. Building on the foundations, we show that Pence and Ramsey’s fitness—F—can be partitioned into fourths: adaptedness, robustness of adaptedness, and two facets of evolvability. Conceptualizing these last three components forces us to consider the role played by grains of description of both organisms and the environment when thinking about long-term fitness. They track the possibility that there could be a change in type in a daughter population as a way of responding to environmental challenges, or that the type persists in the face of novel environments. We argue that these components are just as salient as adaptedness for long-term fitness. Together, this decomposition of F provides a more accurate picture of the factors involved in long-term evolutionary success.

Biography:

Prof. Pierrick Bourrat is a Senior Lecturer and DECRA Fellow at Macquarie University, Sydney, Australia. He specialises in philosophy of biology. Together with Paul Griffiths, I head the Theory and Method in Biosciences group. From 2017 to 2020 I was a Macquarie University Research Fellow. He completed a PhD in philosophy of biology at the University of Sydney in 2015. His work focuses on core concepts of evolutionary theory, such as fitness and heritability, as well as evolutionary transitions in individuality. His other interests include causation, the interplay between biological and cultural evolution and the evolution of religious beliefs.