If, in schools, we keep teaching that history is divided into American history and Chinese history and Russian history and Australian history, we're teaching kids that they are divided into tribes. And we're failing to teach them that we also, as human beings, share problems that we need to work together with.

Modern scientific knowledge appeared piecemeal. Historians wrote about human history; physicists tackled the material world; and biologists studied the world of living organisms. But there were few links between these disciplines, as researchers focused on getting the details right.