Punctuated equilibrium and species selection: what does it mean for one theory to suggest another?

Abstract

McMullin (In: Cohen et al. (eds.) Essays in memory of Imre Lakatos, 1976, In: Leplin (ed.) Scientific realism, 1984) argues that fertility is a theoretical virtue. He thinks of a fertile theory as one whose central metaphors suggest new directions for theoretical development, where those new developments help solve previous problems and anomalies. Nolan (Br J Philos Sci 50:265-282, 1999) argues that fertility in this sense is not a distinctive theoretical virtue in its own right. Rather, Nolan thinks that fertility is reducible to predictive novelty. This article explores the relationship between punctuated equilibrium (PE) and species selection in the light of this philosophical debate about the nature of theoretical fertility, or suggestiveness. I argue that (1) PE suggests, but does not imply, that species selection is a mechanism of evolution; (2) the suggestiveness in this case is not reducible to predictive novelty; (3) species selection is not a metaphorical extension of PE; and (4) getting clear about the way in which PE suggests species selection can help solve a puzzle about punctuated equilibrium. The puzzle is that Eldredge and Gould's initial presentation of PE seems to presuppose a minimalist or extrapolationist view of macroevolution, even though many scientists take PE to challenge that minimalist view.