Where did we come from? Though researchers have done much work on this question in recent years, the answer remains elusive. InThe Spark of Life, Christopher Wills and Jeffrey Bada examine the enduring mysteries surrounding life's origin: Did life arise on earth or on some other planet? What did the earliest primitive organisms look like? Were they based on RNA, DNA, or on something we would hardly recognize today? Untangling a century of contentious debate, the authors explore current theories of "the source"-from Martian meteors to hydrothermal vents-and then present their own elegant and compelling 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. The book ends with a whirlwind tour of one of the most exciting scientific endeavors: the search for extraterrestrial life. Knowing exactly how life began on Earth will not only teach us more about ourselves, it will bring us much closer to finding life elsewhere.

Christopher Wills is Professor of Biology at the University of California at San Diego.