As important as philosophy and moral fiction are, they’re just ideas if they’re not counterbalanced with an understanding of our biology and psychology.
The Moral Animal by Robert Wright
This is probably the definitive beginner text on evolutionary psychology and one of the easiest to get into. It’s a little depressing at first, realizing how ruthless many of our so called “good” feelings are. But then you realize that truth is better than ignorance, and you emerge seeing the world as it truly is for the first time. Also, a similar read is Why Beautiful People Have More Daughters (Amazon), which is more of a Q&A approach to the subject and has contemporary edge.
Sex on the Brain by Deborah Blum
One of the better books on evolutionary biology that focuses almost entirely on the biological and psychological differences between men and women. It’s written by a journalist (who cites scientists) so it’s easy to read if you’re not studied in the field. If you want to get into evolutionary psychology–which you totally should–this is a good starting point because it covers all the basics. Essentially, it discusses how men and women have benefited evolutionarily through different behaviors and strengths so it would only make sense that they would have developed into two very different entities.
I would also recommend: The Game by Neil Strauss (Amazon), (as well as The Truth (Amazon)), The God Delusion by Richard Dawkins (Amazon), The Evolution of Desire by David Buss (Amazon), and the The Origins of Virtue by Matt Ridley (Amazon) which asserts that we had morality before religion, trade before capitalism and cooperation before government.