To explain the mystery of how life evolved on Earth, Nick Lane explores the deep link between energy and genes.

Why is life the way it is? For two billion years, bacteria continually evolved without ever changing their basic form. Then single-celled organisms made the jump into complex life. In The Vital Question, award-winning author and biochemist Nick Lane argues that the evolution of multicellular life—the kind found in fungi, plants, animals, and humans—was contingent on a single event: the first successful prokaryotic endosymbiosis, or a bacterium living within another bacterium. Building on the pillars of evolutionary theory, Lane’s hypothesis draws on cutting-edge research into the link between energy and genes to suggest a novel account of cellular evolution and large-scale life as we know it. At once rigorous and enchanting, the conclusions in The Vital Question not only explain the vast sweep of evolutionary history but also provide insights that stretch forward into our understanding of sex, speciation, and the complexity of human life.