A few years ago, I spent a week in the village of Salamaua on the Huon Gulf coast of Papua New Guinea (PNG). I delighted in swimming in the warm tropical waters that lap the village. After a dip or two, I wondered if there might be crocodiles about. My hosts told me that there was a resident crocodile; sometimes it came through the village at night, but I need not worry. In generations past, Salamauans and crocodiles had come to an agreement not to hurt each other, and since then the people of the village and their guests had been perfectly safe. I kept swimming.