European migration to the Americas had few, if any, positive effects on the native populations. The Indians' contact with settlers led to their displacement, subjugation and death from disease and warfare. These negative consequences far outweighed the Europeans' good intentions, which included efforts to Christianize and educate America's original inhabitants. Researchers estimate that the native population in America declined by nearly 50 percent due to disease alone, beginning with the natives' first contact with European explorers in the 16th century.

Europeans Bring Diseases

When Spanish conquistador Hernan Cortes arrived with his army in the Aztec capital, Tenochtitlan, in 1521, he found the city in the grip of a smallpox epidemic. The epidemic has been traced to an African slave sailing with Spanish soldiers from Cuba to Mexico. By the time Francisco Pizarro arrived in Peru about ten years later, smallpox had decimated a large part of the Inca population. Europeans exploring and settling North America in the 16th and 17th centuries brought smallpox, measles and influenza, diseases usually associated with domesticated livestock. Native Americans, who generally were in better health than Europeans, did not keep livestock and had no immunity to these diseases.

Europeans Disrupt Food Supply

European settlers in North American failed to understand the Indians' concept of maintaining hunting and fishing lands. To the Europeans, land that wasn't cultivated was wasted. To the Indians, even land they sold to the Colonists was still theirs to hunt and fish. This led to many conflicts. In addition, settlers, particularly in the southern Colonies, often let their livestock roam freely. The livestock damaged the environment and changed the ecosystem. This, in turn, endangered the wildlife and diminished the Indians' traditional food supply.

The Effects of Warfare

Warfare between the Indians and European settlers began shortly after the arrival of the first colonists in the early 1600s and lasted for nearly 300 years. Estimates of the Indian population prior to European settlement range from one million to 12 million. By the late 1800s, the population was determined to be about 250,000. It's estimated that at least 10 percent of the population -- representing hundreds of thousands of Indians -- died from violence, torture and the hardships of being forcibly relocated. Many also were sold into slavery. On the western frontier, in particular, there was little oversight of Indian and settler relations. Personal accounts from the period describe the settlers' attitude as one of favoring extinction of the native population.

Christianization, Coexistence and Captives

European missionaries felt they had an obligation to convert Indians to Christianity. The Puritans believed the Indians to be one of the Lost Tribes of Israel. They built "praying towns" where Indians were educated in the Christian faith. French Jesuit missionaries in Canada established villages where they lived among the Indians, exchanged information about their cultures, and acted as intermediaries between the Indians and fur trappers. Conversely, many European women and children were absorbed into the Indian population after being taken captive. They were adopted into families and often treated very well. Many captives chose to stay with the tribe even after being given an opportunity for freedom.