These days, we are repeatedly reminded - by scientists, by the media, by popular culture - of the looming threat of mass extinction. We're told that human activity is currently producing a sixth mass extinction. Indeed, there is a very real concern that the human species may itself be poised to go the way of the dinosaurs, victims of the most recent mass extinction some 65 million years ago. How we interpret the causes and consequences of extinction and their ensuing moral imperatives is deeply embedded in the cultural values of any given historical moment. And, as David Sepkoski reveals, the history of scientific ideas about extinction over the past two hundred years - as both a past and a current process - is implicated in major changes in the way Western society has approached biological and cultural diversity.