Life on Earth arose nearly 4 billion years ago, bursting forth from air, water, and rock. Though the process obeyed all the rules of chemistry and physics, the details of that original event pose as deep a mystery as any facing science. How did non-living chemicals become alive? While the question is (deceivingly) simple, the answers are unquestionably complex. Science inevitably plays a key role in any discussion of life's origins, dealing less with...