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 indigenous peoples.

European immigrants to the Americas wanted a familiar diet, so they searched for climatic zones favorable to familiar crops. 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. Europeans also introduced domestic livestock and horses, which allowed for faster travel and easier transport of heavy loads. In turn, Europeans returned home with many food crops that became central elements of their diet, such as potatoes, maize (corn), and tomatoes. (See “Living in the Past: Foods of the Columbian Exchange.”)

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. In Europe, infectious diseases like smallpox, measles, and influenza — originally passed on from domestic animals living among the population — killed many people each year. Given the size of the population and the frequency of outbreaks, in most of Europe these diseases were experienced in childhood, and survivors carried immunity or resistance. Over centuries of dealing with these diseases, the European population had had time to adapt. Prior to contact with Europeans, indigenous peoples of the New World suffered from insect-borne diseases and some infectious ones, but their lack of domestic livestock spared them the host of highly infectious diseases known in the Old World. The arrival of Europeans spread these microbes among a completely unprepared population, and they fell victim in vast numbers (see “Indigenous Population Loss and Economic Exploitation.”) 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 fourteenth century, first on Asia and then on Europe. The world after Columbus was thus unified by disease as well as by trade and colonization.