As I browsed the new papers published this week in the Proceedings of the National Academy of Sciences, I was brought up short by this frolicsome picture. It’s a nice example of the visual display of information done right. It shows the spread of primates 55 million years ago across the Northern Hemisphere. I’m always game to learn about what primates were up to in Wyoming and Greenland. But this picture–and the paper that goes with it–have an extra value. They offer some clues to what sort of world we may be creating by pumping billions of tons of carbon dioxide into the atmosphere.

Paleontologists have known for a long time that something remarkable happened around the time the