A strength of kin-selection theory for explaining the evolution of altruism is that it generates multiple hypotheses that can fail in resulting tests, forcing principles to be re-examined. Lessons can be learned from one such failure discussed by Nowak et al.: the haplodiploid hypothesis (Nature 466, 1057–1062; 2010).

With haplodiploidy, fertilized eggs become females and unfertilized ones become males. Thus, females can have higher fitness if they raise their full sisters instead of their own offspring.

This prediction was not wrong in the sense that it arose from flawed mathematics. Indeed, practitioners of the natural-selection approach championed by Nowak et al. could have made the exact same prediction. It fails experimentally because a basic assumption is not met in nature: females rarely get the opportunity preferentially to raise full sisters.

Theoretical papers that developed more viable alternative scenarios also used inclusive fitness methods (for example, see D. C. Queller Proc. Natl Acad. Sci. USA 86, 3224–3226; 1989). This robust predict–fail–reevaluate triumvirate is why kin selection has been the main informative model of choice in the past and why it should continue to help us understand the evolution of cooperation and conflict.

See also: Better living through physics, Inclusive fitness is just bookkeeping, Call for a return to rigour in models