Where did we come from, biologically speaking? In this hour of Science Friday, Ira talks with biologist Richard Dawkins about his latest book, 'The Ancestor's Tale,' a tour through the evolution of life on Planet Earth.

Plus, researchers in Spain say they've made a fossil find that could be close to the last common ancestor of all great apes and humans. We'll find out about the new member of the family tree. Call in with your questions and comments at 1-800-989-8255 (3-4 Eastern).

During this hour, Ira and Dr. Dawkins got to talking about how hard it is to remember the names of various geologic time periods. Ever helpful, our listeners stepped up to the plate with a collection of mnemonic devices.