Essentially a threadjack, but Michael Tomasello makes an excellent case (http://www.2think.org/humancognition.shtml) that the major difference between humans and other animals is something he calls the "ratchet effect" of culture and literacy, such that useful things learned don't need to be either discovered anew by each generation or biologically inherited.

Tomasello works with great apes and small children, especially on language acquisition. He’s very anti-Chomsky and anti-Pinker in his conclusions, if you're familiar with those two, but he doesn’t condemn them much in his arguments.