Exploring the development of humankind between the Old World and the New�from 15,000 BC to AD 1500�the acclaimed author of Ideas and The German Genius offers a groundbreaking new understanding of human history. Why did Asia and Europe develop far earlier than the Americas? What were the factors that accelerated�or impeded� development? How did the experiences of Old World inhabitants differ from their New World counterparts�and what factors influenced those differences? In this fascinating and erudite history, Peter Watson ponders these questions central to the human story. By 15,000 BC, humans had migrated from northeastern Asia across the frozen Bering land bridge to the Americas. When the world warmed up and the last Ice Age came to an end, the Bering Strait refilled with water, dividing America from Eurasia. This division�with two great populations on Earth, each unaware of the other�continued until Christopher Columbus voyaged to the New World in the fifteenth century. The Great Divide compares the development of humankind in the Old World and the New between 15,000 BC and AD 1500. Watson identifies three major differences between the two worlds�climate, domesticable mammals, and hallucinogenic plants�that combined to produce very different trajectories of civilization in the two hemispheres. Combining the most up-to-date knowledge in archaeology, anthropology, geology, meteorology, cosmology, and mythology, this unprecedented, masterful study offers uniquely revealing insight into what it means to be human.