Facing the facts

Counting from the first papers by Hamilton (1963, 1964) on the principles of kin selection, it is now more than four decades that arguments about the evolution of cooperation and altruism have played an important role in evolutionary theorizing. Much of the work is characterized by ingenuity and brilliance, possibly because the evolution of cooperation is crucial for the understanding of biological organization and, in particular, for the understanding of our own species, making it an interesting topic for some of the strongest theoreticians. After this extended period of high-quality conceptual inquiry, it seems reasonable to ask whether theory in the field is becoming more successful at interpreting facts and inspiring decisive empirical observation, which is after all a main purpose of theory in the natural sciences. From such a perspective, an interesting classification of models ought to make distinctions that encourage critical empirical investigation. The target review by Lehmann & Keller (2006, L & K) achieves this aim in at least one important instance, by insisting on distinguishing whether or not interactions occur between related individuals. However, in other regards their classification seems less helpful in promoting contact between theory and observation.