Fire is evolving. The three necessary ingredients for fire - heat, fuel, and oxygen - each appeared at different times in geological history, meaning that fire wasn't always around on Earth's surface. Fire historian Steve Pyne describes the origin and evolution of fire over the past 420 millions years on Earth, including history's true Promethean moment. In a bonus segment, producer Mike Osborne chats with paleoclimate scientist Jud Partin about his new publication exploring the Younger Dryas, the most recent time in Earth's history to experience abrupt climate change. Hear Jud describe what happened as Earth left the last ice age and why he's still optimistic about abrupt climate change today.