Lieberman compares Adam and Eve’s expulsion from Eden to humans’ transition to agrarian lifestyles. Agriculture supports a larger population but has consequences, including overcrowding, disease, poor-quality diets, increased labor requirements, social strain, and an increased risk of starvation. Farming emerged in at least seven separate locations shortly after the end of the Ice Age. The Holocene, the current geological period, has warmer and more consistent weather; the favorable weather and the stress of feeding a growing population were the likely catalysts of agriculture.

Mediterranean archaeological sites show a population boom near the end of the Ice Age—a period called the Natufian. The Natufian was interrupted by the Younger Dryas, a return to Ice Age conditions 12,800 years ago. Some Natufians returned to nomadic lifestyles while others remained in their permanent settlements and practiced farming. Over 1,000 years, an agricultural economy emerged, and humans in the area domesticated several species, leading to a new period: The Pre-Pottery Neolithic A (PPNA), characterized by large settlements, mud-brick houses, stone food processing tools, and figuring and plaster art.

In Asia, rice and millet farming began around 9,000 years ago; in Mesoamerica, squash farming began 10,000 years ago followed by corn and other crops, which spread throughout the New World.