The "meaning of it all” hinges on whether we arose by chance, or whether there is some cosmic imperative behind our existence. Forty years ago, geneticist Jacques Monod bleakly concluded that we are alone, a freak accident in an empty universe. Since then, our understanding of biology, evolution and the cosmos has been transformed. Nick Lane will argue that, while the origin of life was thermodynamically nearly inevitable, the birth of complex life was another matter altogether.