At a research site in Fongoli, Senegal, a female chimpanzee breaks off a branch, chews the end to make it sharp, and then uses this rudimentary spear to skewer a tasty bush baby hiding inside a hollow tree. It's an astonishing breakthrough for primate researchers—the first time anyone has documented a chimpanzee wielding a carefully prepared, preplanned weapon. But it's only the latest in a slew of extraordinary new findings about ape behavior.

The more researchers learn about the great apes—chimpanzees, bonobos, gorillas, and orangutans—the more evidence they find of creative intelligence. What, then, is the essential difference between them and us? "Ape Genius," a NOVA-National Geographic special, explores that provocative question and examines research that is illuminating the ape mind. Bit by bit, investigators are finding an explanation for why the non-human great apes never made the breakthrough into a human-style culture that builds on the achievements of previous generations.