In Earth’s 4.5-billion-year history, over 5 billion species have gone extinct. In Extinction: What Happened to the Dinosaurs, Mastodons, and Dodo Birds? explore the mysteries of extinction on the planet – past, present, and future. Paleontologists, geologists, and other scientists follow clues left behind in rocks to determine the reasons for extinction. This scientific detective work is particularly focused on the five mass extinctions that have occurred on Earth, events which killed over 75% of species at one time. Extinction then explores the role that humans have had in extinction since the dawn of man, and whether humans are responsible for initiating a sixth mass extinction.