I think The Neandertal Enigma gets into some of the evolutionary aspects of psychology and religion later in the book. But of course, that's all speculation, so not really very helpful in this sort of debate.

There's also a ... Brin(?) story about a plague that causes everyone to be altruistic -- sort of the flipside to the paradox of why a parasite should kill off its host... Oh, right, in this case it made people really want to donate blood.