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? The authors examine the latest research - in fields ranging from molecular biology to astronomy - on questions surrounding life's origins. They untangle a century of contentious debate and explore many theories, assessing the probability of everything from asteroids and Martian rocks to 'primordial soup' and volcanic vents. They 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 endeavours - the search for extra-terrestial life.