The economics of altruism and cooperation in class‐structured populations: what's in a cost? What's in a benefit?

Lehmann & Keller (2006, and hereafter referred to as either ‘the authors’ or L&K) have identified the cost-tobenefit ratio, C/B as being a principal factor in the evolution of altruism and cooperation. The authors argue that this ratio (or some equivalent version) cannot exceed a given threshold if a selective advantage of altruism or cooperation is to exist. Of course, many biologists will readily recognize Hamilton’s (1964) rule as a special case of this result. An actor is willing to pay a cost, C, to give a benefit, B, to a recipient whenever