Explanations that refer to evolvability are concerned with the ´evolutionary potential´ of populations and lineages. They make claims about the relationship between relatively independent lower-order causal features of populations and lineages and higher-order patterns in the tree of life. The ´evolutionary potential´ of interest here is best thought of as a conditional probability -- the probability of a population or lineage changing over time with respect to some feature or features given the state of the population or lineage at a particular starting point. In the first half of this paper, the author provides a formal framework via which to represent evolvability using these conditional probabilities and therefore clarify the meaning of common statements in the field of the form ´x is more evolvable than y´ and ´a contributes to the evolvability of y.´ Via this approach it also becomes clear that discussions of evolvability must concern more than merely the supply of variation to selection and the nature of that supply supply. In the second half of this paper the author explores what these other phenomena are and some methods via which we can represent their relative contribution to evolvability.
Rachael Brown is a final year PhD candidate in the School of Philosophy at the Research School of Social Sciences, Australian National University in Canberra supervised by Kim Sterelny (chair), Paul Griffiths, and Brett Calcott. She is also a member of Tempo & Mode: Centre for Macroevolution and Macroecology, ANU. Prior to this she completed degrees in Zoology and the History and Philosophy of Science at the University of Melbourne. Her primary research interests lie at the intersection of philosophy, evolutionary biology and the study of animal behavior, and her doctoral thesis is entitled ´Understanding Behavioural Innovation, Novelty and Evolvability.´