Between the fifteenth and seventeenth centuries Africa and the Americas became the first areas of the world to experience significant consequences from European expansion. On both sides of the Atlantic the arrival of Europeans resulted in demographic and biological changes, political upheavals, and the introduction of new trade patterns, religions, and technologies. But the depth and extent of European impact on the two regions was far different Africa was affected by the Europeans, but the Americas were transformed.

          The European presence in Africa primarily meant trade, trade in which human beings -- slaves -- became the most lucrative commodity. However, even in the eighteenth century, when the Atlantic slave trade reached its peak and was a source of misery and death for millions, most of the continent was unaffected. Even where slaving was most intense, traditional African institutions remained largely intact. Europeans maintained no permanent colonies in sub-Saharan Africa until the Dutch began to settle in south Africa in 1652. On the other side of the Atlantic, however, by 1650 the Spaniards and Portuguese ruled and economically dominated Mexico and all of Central and South America, and several permanent European settlements had been established on North America's Atlantic coast and the St. Lawrence River Basin. The result was catastrophe for Native Americans. Political structures disintegrated, millions of people died of Old World diseases, and traditional patterns of life and belief managed only a tenuous survival.

          What explains the divergent experiences of Africa and the Americas despite the two areas' broad technological and political similarities? A major factor was that Portugal, which led the way in African exploration, trade, and conquest, had a relatively small population and limited resources, and by the sixteenth century shifted most of its energies from Africa to Asia, where until the seventeenth century it dominated the lucrative trade in spices. Later, in the seventeenth and eighteenth centuries, when Spain, England, and France became interested in Africa, the Africans had firearms and were capable of resisting unwanted European encroachment. Two other factors that discouraged European involvement were African diseases such as malaria and yellow fever that were deadly to Europeans and the absence of easily navigable rivers from-the seacoast to the continent's interior.

          Until the nineteenth century Europeans were content to remain in their coastal enclaves and trade with African merchants who brought them ivory, pepper, and especially slaves. More aggressive intervention in African affairs ended disastrously, either for the Africans, as in the kingdom of Kongo, or for the Europeans, as was ultimately the case with the Portuguese in East Africa.

          European explorers, adventurers, and colonists faced a far different situation in the Americas. They soon discovered that the region contained easily exploitable sources of wealth, such as silver and furs, and land capable of production profitable agricultural goods, such as tobacco and especially sugar cane. They also found that these things were theirs for the taking, not only in the sparsely populated regions of North America and eastern and southern South America but also in more populous areas such as Mexico, Peru, and the Caribbean.

          Although the Europeans' guns, horses, and war (logs gave them a distinct military advantage over the Amerindians, this was not the main reason for the relative ease of their conquests. In Mexico, for example, under normal circumstances several hundred Spaniards, even with their cannons and Amerindian allies, would have been no match for thousands of Aztec warriors with arrows, clubs, lances, and spears. But the Aztecs and all other Native Americans had to contend not just with their enemies' weapons but also the Old World bacteria, viruses, and parasites their enemies were carrying in their bodies. Because of their long isolation Amerindians lacked immunity to such Old World sicknesses as diphtheria, measles, trachoma (severe conjunctivitis), chicken pox, whooping cough, yellow fever, influenza, dysentery, and smallpox. Thus, the arrival of a few Europeans and Africans in the Americas had immediate and devastating consequences. On the island of Hispaniola, where Columbus established the first Spanish settlement in the New World in 1492, the population plummeted from one million to only a few thousand by 1530. Within fifty years after the arrival of Cortes in Mexico, the estimated population of the Aztec Empire fell by 90 percent. Ultimately, no part of the Americas was untouched.

          Such human devastation not only made it relatively easy for the Europeans to conquer or displace the Native Americans but also led to the enslavement of Africans in the New World. The epidemics created labor shortages that European plantation owners in Brazil, the West Indies, and southeastern North America sought to overcome by importing and enslaving Africans. Before the transatlantic slave trade ended, approximately nine million Africans were sold into slavery. These Africans too were indirect victims of the bacilli, viruses, and parasites carried across the Atlantic to the New World in the early years of European expansion.