The Big Ratchet is the story of the ratchets: the technologies and innovations, big and small, that propelled our species from hunters and gatherers on the savannahs of Africa to shoppers in the aisles of the supermarket. Our species long lived on the edge of starvation. Now we produce enough food for all 7 billion of us to eat nearly 3,000 calories every day. This is such an astonishing thing in the history of life as to verge on the miraculous. The Big Ratchet is the story of how it happened.