After the IceTwenty thousand years ago, Earth was in the midst of an ice age. Then global warming arrived, leading to massive floods, the spread of forests, and the retreat of the deserts. By 5,000 BC, a radically different human world had appeared. In place of hunters and gatherers, there were farmers; in place of transient campsites, there were towns. The foundations of our modern world had been laid, and nothing that came afterthe Industrial Revolution, the