The travel of people and goods between the Old and New Worlds led to an exchange of animals, plants, and diseases, a complex process known as the Columbian exchange. As we have seen, the introduction of new diseases to the Americas had devastating consequences. But other results of the exchange brought benefits not only to the Europeans but also to native peoples.

Everywhere they settled, the Spanish and Portuguese brought and raised wheat with labor provided by the encomienda system. Grapes and olives brought over from Spain did well in parts of Peru and Chile. Perhaps the most significant introduction to the diet of Native Americans came via the meat and milk of the livestock that the early conquistadors brought with them, including cattle, sheep, and goats. The horse enabled both the Spanish conquerors and native populations to travel faster and farther as well as to transport heavy loads.

In turn, Europeans returned home with many food crops that became central elements of their diet. Crops originating in the Americas included tomatoes as well as many varieties of beans, squash, pumpkins, and peppers. One of the most important of such crops was maize (corn). By the late seventeenth century maize had become a staple in Spain, Portugal, southern France, and Italy, and in the eighteenth century it became one of the chief foods of southeastern Europe. Even more valuable was the nutritious white potato, which slowly spread from west to east—to Ireland, England, and France in the seventeenth century, and to Germany, Poland, Hungary, and Russia in the eighteenth, contributing everywhere to a rise in population.

While the exchange of foods was a great benefit to both cultures, the introduction of European pathogens to the New World had a disastrous impact on the native population. The wave of catastrophic epidemic disease that swept the Western Hemisphere after 1492 can be seen as an extension of the swath of devastation wreaked by the Black Death in the 1300s, first on Asia and then on Europe. The world after Columbus was thus unified by disease as well as by trade and colonization.