As others have pointed out, writing is a very recent phenomenon, but your intuition seems correct in general - what sets humans apart from chimps and bonobos is efficient transfer learning to future generations. If you are interested, The Cultural Origins of Human Cognition by Michael Tomasello makes this point in detail. Tomasello argues that chimps, while being impressive learners and problem solvers in some ways, actually have extremely inefficient cultural transfer, which prevents runaway cultural evolution that has happened in humans.