Spanning millennia and continents, here is a stunningly revealing history of how the distribution of water has shaped human civilization. Giulio Boc­caletti describes how these societies were made possible by sea-level changes from the last glacial melt and incisively examines how this type of farming led to irrigation and multiple cropping, which, in turn, led to a population explosion and labor specialization. We see with clarity how irrigation’s structure informed social structure (inventions such as the calendar sprung from agricultural necessity); how in ancient Greece, the communal ownership of wells laid the groundwork for democracy; how the Greek and Roman experiences with water security resulted in systems of taxation; and how the modern world as we know it began with a legal framework for the development of water infrastructure.