This film tells the story of a new research project in Kenya and Ethiopia that aims to find answers to the question: What role did the climate play in human evolution? The film follows geologists and anthropologists as they drill into ancient lake bed sediments at remote locations in the African Rift Valley, where the famed hominin fossils Lucy and Turkana Boy were discovered. At the drill sites scientists collect sediments and send samples to laboratories around the world. The samples reveal, for the first time, a precise record of climate change over the past 3.4 million years. New questions arise as to how those changes may have affected human evolution. These new findings, just emerging, may give us valuable insights into dealing with the global climate changes that are happening today.