I mention this book because it also addresses the idea of "moral" behavior, not as a chemical reaction, but as a contributing factor to natural selection and survival of a species.
You might enjoy it.
Dr Zak covers this in fairly high detail, he studied the behavior of two certain types of shrew, one that was social and one that was anti-social. The anti-social shrew had not evolved as many oxytocin receptors. It is meant to be a startlingly large part of natural selection, co-operation rather than competition, but competition of different groups with testosterone used as the other side of the scale (to enhance aggression and dominance over rivals)
I will look it up though! Definitely. Is there a version of it on project Gutenburg?