If you were to visit the Great Basin and Colorado Plateau a thousand years ago, you'd find conditions remarkably familiar to the present. The climate was warm, but drier than today. There were large populations of Indigenous people known as the Fremont, a who hunted and grew crops in the area. With similar climate and moderate human activity, you might expect to see the types of wildfires that are now common to the American West: infrequent, gigantic and devastating. But you'd be wrong.