Life on Earth—three simple words for a journey spanning billions of years. This program presents 10 milestones that have helped to tell life’s story: Walter Alvarez’s K-T asteroid theory of dinosaur extinction; the first identification of dinosaur fossils; Stanley Miller’s simulation of the early atmosphere, leading to organic compound formation; Robert Ballard’s discovery of hydrothermal vent ecosystems; Charles Walcott’s analysis of the Burgess Shale; the Linnaean classification system; Darwin’s theory of natural selection; Donald Johanson’s “Lucy”; Mary Leakey’s Laetoli footprints; and Michel Brunet’s Toumai skull. A Discovery Channel Production. (46 minutes)