The tale of a massive, devastating flood appears not only in the Bible but also in other ancient writings, often in similar terms, suggesting that it records a real and singularly memorable event. Ryan and Pitman, who are senior scientists at Columbia University’s Lamont-Doherty Earth Observatory, think the event might have been a huge and prolonged cascade of water from the Mediterranean that broke through a natural dam in the Bosporus Strait and plunged into what was then a freshwater lake and is now the Black Sea. They present both geologic and archaeological evidence for the flood, dating it at about 5600 B.C. “The Bosporus flume roared and surged at full spate for at least three hundred days,” they write. The cascade inundated 60,000 square miles of land, forcing the people living in the region to disperse. The book explores the question of who those people were and where they went; it also examines the tradition of oral storytelling that could have passed the flood story from generation to generation.