In this provocative and far-reaching book, internationally acclaimed physicist and writer Paul Davies confronts one of science's great outstanding mysteries -- the origin of life.

Three and a half billion years ago, Mars resembled earth. It was warm and wet and could have supported primitive organisms. If life once existed on Mars, might it have originated there and traveled to earth inside meteorites blasted into space by cosmic impacts?

Davies builds on recent scientific discoveries and theories to address larger questions of existence: What, exactly, is life? Is it the inevitable by-product of physical laws, as many scientists maintain, or an almost miraculous accident? Are we alone in the universe, or will life emerge on all earthlike planets? And if there is life elsewhere in the universe, is it preordained to evolve toward greater complexity and intelligence?

Through his search for answers to these questions, Davies explores the ultimate mystery of mankind's existence -- who we are and what our place might be in the unfolding drama of the cosmos.