The premise is that morality comes out of altruistic reciprocity which evolves genetically. But game theory shows that it is easy to learn reciprocity. In other words morality and religion are consonant with our ability to learn, but not necessarily a genetic result. It's a genetic result of the smart people learning how to be altruistic among other things, at best. I'd say that morality comes more out of a culture of learned behavior, as described in IX, pp.
Irons uses a Lamarckian theory of evolution.