Hamilton's rule: a non-causal explanation?


More than fifty years since Hamilton’s (1963; 1964) groundbreaking work on social evolution, the evolutionary explanation of altruism and cooperation is an ongoing topic of research. More recently, high-profile biologists Nowak et al. (2010) have joined forces in criticizing the relevance of inclusive fitness theory for evolutionary research. Their article resulted in a fierce response by over one hundred evolutionary biologists (Abbot et al. 2011) and subsequently generated a growing body of highly technical literature. In this paper, we reinforce the case for the considerable value of the general version of Hamilton’s rule in explaining the evolution of social traits. In particular, we argue that although the rule can have an organizing role in social evolution research (Birch 2014; 2017), it does not explain in virtue of providing an organizing framework. Instead, we argue it either provides an explanation by constraint or a non-causal counterfactual explanation.