Throughout its long history, life has been a force of planetary transformation, remaking the air, the rocks, the landscapes, even painting the color of the sky and increasing the variety of Earth’s minerals. But are the histories of life and Earth just one thing after another, or is there an underlying pattern that we can make sense of? Here, I argue that there is a pattern, and that life-Earth history can be understood as a sequence of five epochs, each of which corresponds to the evolution of lifeforms that can access a new source of energy. With each new epoch, the diversity of life has become greater, ecosystems have become richer, and life has increased its impact on the planet. This framework of energy expansions provides a way to think about current human impacts upon the Earth—and about the probable trajectories of life-planet systems elsewhere in the cosmos.
Olivia Judson is an evolutionary biologist and writer. Her award-winning book, Dr Tatiana’s Sex Advice to All Creation: The Definitive Guide to the Evolutionary Biology of Sex, has been translated into more than 15 languages, and was also made into a TV show. For two years, she was the author of a popular online column in The New York Times; she has also contributed to publications such as National Geographic, The Guardian, and The Economist. Affiliated with both Imperial College London and the Freie Universität Berlin, she is presently writing a history of life and Earth.