Bookninja has two links on the subject today, one from The Guardian and another from The New York Times, which provides us with the theory in a nutshell:

Just as Charles Darwin studied animals to discover the patterns behind their development, Literary Darwinists read books in search of innate patterns of human behavior: child bearing and rearing, efforts to acquire resources (money, property, influence) and competition and cooperation within families and communities. They say that it's impossible to fully appreciate and understand a literary text unless you keep in mind that humans behave in certain universal ways and do so because those behaviors are hard-wired into us. For them, the most effective and truest works of literature are those that reference or exemplify these basic facts.

We've discussed this before. It's silly, but it's a wise silly, and honestly I think Darwinism probably has a place alongside Marxism, feminism, race-consciousness, deconstructionism, and other investigative tools in the literary theorist's toolkit. It has it uses. But no -ism can explain anything, and all -ists would be wise not to try.