Humanity is the keystone species for fire on Earth: fire is what we do that no other creature does. But our firepower underwent a phase change when we went from burning living landscapes to burning lithic ones (that is, fossil fuels). What had been an interglacial period between ice ages increasingly resembles a fire age — even climate change has become a subnarrative of fire history. The Pleistocene is yielding to a Pyrocene, and what began as a mutual-assistance pact is looking more like a Faustian bargain. Steve Pyne is an emeritus professor at Arizona State University best known for his research into the history of fire and humanity.