The ancestors of today's American Indigenous peoples were the Paleo-Indians; they were hunter-gatherers who migrated into North America. The most popular theory asserts that migrants came to the Americas via Beringia, the land mass now covered by the ocean waters of the Bering Strait. Small lithic stage peoples followed megafauna like bison, mammoth (now extinct), and caribou, thus gaining the modern nickname "big-game hunters." Groups of people may also have traveled into North America on shelf or sheet ice along the northern Pacific coast.
Cultural traits brought by the first immigrants later evolved and spawned such cultures as Iroquois on North America and Pirahã of South America. These cultures later developed into civilizations. In many cases, these cultures expanded at a later date than their Old World counterparts. Cultures that may be considered advanced or civilized include Norte Chico, Cahokia, Zapotec, Toltec, Olmec, Maya, Aztec, Chimor, Mixtec, Moche, Mississippian, Puebloan, Totonac, Teotihuacan, Huastec people, Purépecha, Izapa, Mazatec, Muisca, and the Inca.
After the voyages of Christopher Columbus in 1492, Spanish, Portuguese and later English, French and Dutch colonial expeditions arrived in the New World, conquering and settling the discovered lands, which led to a transformation of the cultural and physical landscape in the Americas. Spain colonized most of the American continent from present-day Southwestern United States, Florida and the Caribbean to the southern tip of South America. Portugal settled in what is mostly present-day Brazil while England established colonies on the Eastern coast of the United States, as well as the North Pacific coast and in most of Canada. France settled in Quebec and other parts of Eastern Canada and claimed an area in what is today the central United States. The Netherlands settled New Netherland (administrative centre New Amsterdam - now New York), some Caribbean islands and parts of Northern South America.
European colonization of the Americas led to the rise of new cultures, civilizations and eventually states, which resulted from the fusion of Native American and European traditions, peoples and institutions. The transformation of American cultures through colonization is evident in architecture, religion, gastronomy, the arts and particularly languages, the most widespread being Spanish (376 million speakers), English (348 million) and Portuguese (201 million). The colonial period lasted approximately three centuries, from the early 16th to the early 19th centuries, when Brazil and the larger Hispanic American nations declared independence. The United States obtained independence from England much earlier, in 1776, while Canada formed a federal dominion in 1867. Others remained attached to their European parent state until the end of the 19th century, such as Cuba and Puerto Rico which were linked to Spain until 1898. Smaller territories such as Guyana obtained independence in the mid-20th century, while certain Caribbean islands and French Guiana remain part of a European power to this day.
The specifics of Paleo-Indian migration to and throughout the Americas, including the exact dates and routes traveled, are subject to ongoing research and discussion. The traditional theory has been that these early migrants moved into the Beringia land bridge between eastern Siberia and present-day Alaska around 40,000 – 17,000 years ago, when sea levels were significantly lowered due to the Quaternary glaciation. These people are believed to have followed herds of now-extinct pleistocene megafauna along ice-free corridors that stretched between the Laurentide and Cordilleran ice sheets. Another route proposed is that, either on foot or using primitive boats, they migrated down the Pacific Northwest coast to South America. Evidence of the latter would since have been covered by a sea level rise of a hundred meters following the last ice age.
Archaeologists contend that the Paleo-Indian migration out of Beringia (eastern Alaska), ranges from 40,000 to around 16,500 years ago. This time range is a hot source of debate. The few agreements achieved to date are the origin from Central Asia, with widespread habitation of the Americas during the end of the last glacial period, or more specifically what is known as the late glacial maximum, around 16,000 – 13,000 years before present.
The American Journal of Human Genetics released an article in 2007 stating "Here we show, by using 86 complete mitochondrial genomes, that all Indigenous American haplogroups, including Haplogroup X (mtDNA), were part of a single founding population." Amerindian groups in the Bering Strait region exhibit perhaps the strongest DNA or mitochondrial DNA relations to Siberian peoples. The genetic diversity of Amerindian indigenous groups increase with distance from the assumed entry point into the Americas. Certain genetic diversity patterns from West to East suggest, particularly in South America, that migration proceeded first down the west coast, and then proceeded eastward. Geneticists have variously estimated that peoples of Asia and the Americas were part of the same population from 42,000 to 21,000 years ago.