We’ve always assumed that humans are the only animal to engage in economic activity. We even have a name for ourselves, Homo economicus, that enshrines the idea of ourselves as rational economic actors. But what if we have that completely turned around? A theory gaining currency in biology suggests that non-human animals are much more rational economic actors than we are. I co-produced this episode of Freakonomics Radio (with Brian Gutierrez) all about biological markets among primates, fish, and fungi.