Human morality is composed of three elements: prosocial behaviour, a normative imperative, and the tendency to adjust the boundaries of the social network to which these apply in a flexible, self-interested fashion. A credible case for human uniqueness can be made for the last element only. Because defining social boundaries can be done rationally , the intersection of this tactical approach with the psychological bases underlying the first two elements can help resolve the conflict between emotion and Kant cited by (...) Flack and de Waal. They make a solid case for prosociality, though their discussion of reciprocal sharing has some problems. The perspectives of Boehm and of Sober and Wilson are needed to understand our boundary-adjusting . A satisfying theory of morality's evolution should integrate, not distinguish amongst, the three elements. (shrink)

Emphasis on cross-cultural testing, multiple currencies, multivariate analyses, and levels of explanation makes this an important paper. However, it does not distinguish current function from evolutionary origin; it lacks history. Rather than distinct alternatives, tolerated scrounging (TS), costly signaling (CS), and reciprocal altruism (RA) are likely to be sequentially evolved components of a single integrated system (and kin selection (KS) important only among very close relatives).