Evolutionary Psychology and Literature -- an Objection

I had an email discussion once with a fellow scholar who argued against using evolutionary psychology to understand the actions of Shakespeare's characters on the grounds that Shakespeare couldn't have put in something he didn't know about. The problem with this is that if evolutionary psychology accurately describes human behavior, then Shakespeare doesn't have to have known anything about it to nevertheless use it. I think this may be one of the main errors theorists make in their objection to using things like evolutionary theory and psychology. It's one of the many things literary Darwinists have to overcome. One does have to wonder, though, why Freudian interpretations of Hamlet don't meet with the same objections, though.