 Again, while it may initially seem puzzling that evolution should give rise to psychological altruism, rather than merely to selfishness, there is nothing paradoxical about it: a genetically-based disposition for psychological altruism will evolve just in case such a trait, in the relevant circumstances, promotes the propagation of the genes that bring it about (and does so more effectively than alternative traits produced by rival alleles). And this can again happen in various ways.