Evolutionary Sexuality

I am listening to THE MORAL ANIMAL: WHY WE ARE THE WAY WE ARE by Robert Wright.  The main idea of the first chapter, that men engage in more and less discriminating sex than women because women can have fewer offspring over their lifetime then men, seems a reasonable biological explanation.  In my opinion, society then constructs explanations for this and sets rules to reinforce it.  As Wright notes, the most common of these is the "madonna-whore" dichotomy.