A boy who dreamt of studying behaviors of mammals in African savannah grew up and got a post at the “Primate Research Institute, Kyoto University”, which is a top-ranking institute of this field. Among a bunch of primates, his research subject is Japanese monkeys ( macaca fuscata ), which was and is already a well-researched and thought to be too well-studied that anything unprecedented can be hardly expected to be discovered. Nevertheless, what NAKAGAWA found in some of Japanese monkeys’ behaviors were a sorts of cultures that have something in common with human cultures. It was a new discovery. How could he reach this conclusion? In his talk he will share some clues to make a new discovery.