Maybe Matt Ridley was right?

In "The Rational Optimist," Matt Ridley argued that evolutionary pressure operates not only on genes but on cultural innovations; that "ideas have sex."  This article in Nature compares the transmissibility of genes and folktales:

If folk tales simply spread by diffusion, like ink blots in paper, one would expect to see smooth gradients in these variations as a function of distance. Instead, researchers found that language differences between cultures create significant barriers to that diffusion 

These barriers are stronger than those for the exchange of genes — a message that might be crudely expressed as: “I’ll sleep with you, but I prefer my stories to yours.”