Evaluating inclusive fitness.

Abstract

In 2010, a contentious debate erupted in the field of evolutionary biology in response to an article published in the journal Nature by two mathematical biologists, Martin Nowak and Corina Tarnita, and the renowned evolutionary theorist and entomologist, E.O. Wilson [1]. The article questioned the explanatory efficacy and value of William Hamilton's theory of ‘inclusive fitness’, the reigning theoretical and mathematical basis of decades of empirical research into the evolution of social behaviour—especially cooperative and altruistic behaviour—across the living world. It was an especially polarizing article, given that E.O. Wilson was once one of the main proponents of Hamilton's theory for explaining the evolution of sterile worker castes in insects, and in this article, he revoked his earlier stance. A number of highly critical responses followed, one signed by 137 eminent theoreticians and empiricists in evolutionary biology [2]. The number of scientists rejecting the conclusions of Nowak, Tarnita and Wilson was itself an indication of the nerve that it struck, and also of the continuing centrality of Hamilton's theory to the study of social evolution. But while the years since the publication of the article have witnessed a number of responses and counter-responses that have attempted to settle the disagreements, a definitive consensus is yet to emerge [3–9]. The first task of the present collection is to showcase diverse interpretations, evaluations and uses of inclusive fitness since then, and so to advance towards a better understanding of the role of this theory in diverse areas of research both in the life sciences and beyond. Our aim is to use the recent debates over inclusive fitness not only to highlight interesting divergences between uses of the theory, but also to explore the philosophical questions that it has raised about causality in the study of social evolution, and even about the nature of behaviour in general across diverse species.