Why did the dinosaurs and two-thirds of all living species vanish from the face of the Earth sixty-five million years ago? Throughout the history of life a small number of catastrophic events have caused mass extinction, and changed the path of evolution forever. Two main theories have emerged to account for these dramatic events: asteroid impact, and massive volcanic eruptions, both leading to nuclear-like winter. In recent years, the impact hypothesis has gained precedence, but Vincent Courtillot suggests that cataclysmic volcanic activity can be linked not only to the K-T mass extinction,...