In this portrait of Planet Earth—at just about the mid point of its probable lifespan—a biologist discusses the evolution of the network of life and the crucial role played by humans in determining the future of our world. Unlike most books on earth history, which present the story of life on our planet in terms of one chronological period after another, the author discusses Earth’s teeming diversity in terms of pivotal evolutionary developments. Among these he stresses the importance of symbiosis, sex, and altruism as key determinants of the Earth’s biodiversity. Symbiosis—when single cells began working together—sparked the sudden appearance of complex animals. Much later symbiotic relationships led to flowering plants that depended on animals for pollination and seed dispersal.
