Beginning with Homo erectus's migrations from East Africa to the rest of the continent and to Eurasia a million and a half years ago, the book examines how and why cultures spread throughout the world. Each section of the globe is examined, from the Tigris and Euphrates to the Pacific Islands, the Middle East and Africa. Along the way, technological and scientific leaps, such as sails, cartography and the cure for scurvy are explained. Fernández-Armesto also looks at the important role economics and politics have played in world exploration.