Evolution

Ten milestones that have helped to tell life's story: Walter Alvarez's asteroid theory of dinosaur extinction, the first identification of dinosaur fossils Stanley Miller's simulation of the early atmosphere, 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.