A highly readable survey of the historical prelude to the study of the origins of life, as well as selected areas of current research, including the search for extraterrestrial life.-NatureWhere did we come from? Did life arise on earth or on some other planet? What did the earliest primitive organisms look like? Untangling a century of contentious debate, the authors explore current theories of the source of life-from Martian meteors to hydrothermal vents-and then present their own elegant scenario: Life arose not in the subterranean depths, as many believe, but on Earth's tumultuous surface, where a primitive form of natural selection spawned the first genetic material, perhaps in the form of a proto-virus. Knowing exactly how life began on Earth will not only teach us more about ourselves, it will bring us closer to finding life elsewhere.