Native Americans (also Indians, American Indians, First Nations, Alaskan Natives, Red Indians, or Indigenous Peoples of America) refers to the indigenous inhabitants of Americas prior to the Europeancolonization, and their modern descendants. This term comprises a large number of distinct tribes, states, and ethnic groups, many of them still enduring as political communities.
Depending on the context, the terms "Indian" or "Native American" may or may not include the "Eskimos" (Inuit, Yupik, and Aleut peoples), which are very distinctive in culture and genetics from the other groups. The terms may also be construed to include or exclude the CanadianMétis.
However, the precise epoch and route is still a matter of controversy. Until recently there was a consensus that the migrants crossed the strait around 10,000 BC via the Bering Land Bridge which existed during the last Ice Age (24,000 to 9,000 BC); and that they followed an inland route through Alaska and Canada that had just been freed of its ice cover. There are, however, a number of difficulties in this theory — in particular, growing evidence of human presence in Brazil and Chile by 9,500 BC or earlier . Thus other possibilities, not necessarily exclusive, have been suggested:
The migrants may have crossed the land bridge several millenia earlier, and followed a coastal route thus avoiding the ice-covered interior.
They may have been seafaring people that moved along the coast.
The crossing of the Bering Land Bridge may have occurred during the previous Ice Age, around 35,000 BC.
A more radical alternative is that the Siberians were preceded by migrants from Oceania, who arrived either by sailing across the Pacific Ocean or by following the land route through Beringia at a much earlier date. Proponents of this theory claim that the oldest human remains in South America and in Baja California show distinctive non-Siberian traits, resembling those of Australian Aborigines or the Negritos of the Andaman Islands. These hypothetical American Aborigines would have been displaced by the Siberian migrants, and may have been ancestral to the distinctive Native Americans of the Tierra del Fuego, which are nearly extinct.
Other theories have been advanced as to the origin of Native Americans:
Several amateur historians have suggested that they are descendants of Europeans or Africans who crossed the Atlantic Ocean in prehistory. For instance, some proponents claim to see a resemblance between Olmec physique and African physique. The journalist Thor Heyerdahl demonstrated the possibility of this by sailing from Africa to America on a replica of an Ancient Egyptian reed boat.
Most Native American religions teach that humans were created in America at the beginning of time.
According to Mormon doctrine, most Native Americans are descendants of Lehi and the Nephites, Israelites who came to the Americas c. 590 B.C.
Although there are some experts actively researching these hypotheses, they are not taken seriously by mainstream anthropologists and archaeologists, who consider the genetic, linguistic, and cultural evidence for a Siberian origin overwhelming.
According to that evidence, at least three separate migrations from Siberia to the Americas are highly likely to have occurred. The first wave came into a land populated by the large mammals of the late Pleistocene, including mammoths, horses, giant sloths, and wooly rhinoceroses. The Clovis culture would be a manifestation of that migration; and the Folsom culture, based on the hunting of bison, would have developed from it. This wave eventually spread over the entire continent as far south as Tierra del Fuego.
The second migration brought the ancestors of the Na-Dene peoples. The Na-Dene peoples generally lived in Alaska and western Canada, but some migrated as far south as the Pacific Northwestern US and the American Southwest, and would be ancestral to the Apachess and Navajos.
The third wave brought the ancestors of the Eskimos and the Aleuts. They may have come by sea over the Bering Strait, after the land bridge had disappeared.
In recent years, molecular genetics studies have suggested as many as four distinct migrations from Asia. Most surprisingly, those studies provide evidence of smaller-scale, contemporaneous human migration from Europe, possibly by European peoples who had adopted a lifestyle resembling that of Inuits and Yupiks during the last ice age.
The European colonization of the Americas forever changed the lives and cultures of the Native Americans. In the 15th to 19th centuries, their populations were decimated, by the privations of displacement, by disease, and in many cases by warfare with European groups and enslavement by them. The first Native American group encountered by Columbus, the 250,000 Arawaks of Haiti, were violently enslaved. Only 500 survived by the year 1550, and the group was totally extinct before 1650. Over the next 400 years, if the contacts between the two cultures rarely amounted to outright genocide, they would typically be disastrous for the Native Americans.
In the 15th centurySpaniardss and other Europeans brought horses to the Americas. Some of these animals escaped their owners and began to breed and increase their numbers in the wild. Ironically, the horse had originally evolved in the Americas, but the last American horses died out at the end of the last ice age. The re-introduction of the horse, however, had a profound impact on Native American cultures in the Great Plains of North America. This new mode of travel made it possible for some tribes to greatly expand their territories, exchange goods with neighboring tribes and to more easily capture game.
Europeans also brought diseases against which the Native Americans had no immunity. Sometimes they did this intentionally, but often it was unintentional. Ailments such as chicken pox and measles, though common and rarely fatal among Europeans, often proved fatal to Native Americans. More deadly diseases such as smallpox were especially deadly to Native American populations. It is difficult to estimate the percentage of the total Native American population killed by these diseases, since waves of disease oftentimes preceded Whitescouts and often destroyed entire villages. Some historians have argued that up to 80% of some Indian populations may have died due to European-derived diseases. (See Jeffrey Amherst for an example of germ warfare)
In the 19th century, the Westward expansion of the United States incrementally expelled large numbers of Native Americans from vast areas of its territory, by forcing them into marginal lands in areas farther and farther west, or by outright massacres. Conflicts widely reported at the time as Indian Wars broke out between US forces and many different tribes. Authorities entered numerous treaties during this period, but later abrogated many for various reasons. Well-known military engagements include an atypical Native American victory at the Battle of Little Bighorn in 1876, and the massacre of Native Americans at Wounded Knee in 1890. On January 31, 1876 the United States government ordered all remaining Native Americans to move into reservations or reserves. This set about the downturn of Prairie Culture that developed around the use of the horse for hunting, travel and trading.
The first reported case of white men scalping Native Americans took place in New Hampshire colony on February 20, 1725, though it is thought that Indians learned scalping from Americans who, at times, collected them for bounties.
American policy toward Native Americans has been an evolving process. In the late nineteenth century reformers in efforts to civilize Indians adapted the practice of educating native children in Indian Boarding Schools. These schools, which were primarily run by Christians, proved traumatic to Indian children who were forbidden to speak their native languages, taught Christianism instead of their native religions, and in numerous other ways forced to abandon their Indian identity and adopt European-American culture. There are also documented cases of various abuses at these schools .
Many other attempts were made to deprive the American Indians of their culture, language, and religious beliefs . As recently as the 1960s, Indians were being put into jail for teaching their traditional beliefs. As recently as the 1970s, the BIA was still actively pursuing a policy of "assimilation" , whose goal was to eliminate the reservations and turn Indians into members of mainstream U.S. culture. As of 2004, a major battle, with thousands of deaths , is still being fought against what some consider the theft of Indian land for the coal and urainium it contains. 
Military defeat, cultural pressure, confinement on reservations, forced cultural assimilation, the outlawing of native languages and culture, forced sterilizations, termination policies of the 1950s and 1960s, and slavery have had deleterious effects on Native Americans' mental and ultimately physical health. Contemporary problems include poverty, alcoholism, heart disease, diabetes and New World Syndrome.
In the early 21st century, Native American communities remain an enduring fixture on the United States landscape, in the American economy and in the lives of Native Americans. Communities have consistently formed governments that administer services like firefighting, natural resource management and law enforcement. Most Native American communities have established court systems to adjudicate matters related to local ordinances, and most also look to various forms of moral and social authority vested in traditional affiliations within the community.
Gaming has become a leading industry. Casinos operated by many Native American governments in the United States are creating a stream of gaming revenue that some communities are beginning to use as leverage to build diversified economies. Native American communities have also waged and often prevailed in various legal battles to assure recognition of rights to self-determination and to use of various natural resources. Some of those rights, known as treaty rights are enumerated in early treaties signed with the young United States government. Tribal sovereignty has become a cornerstone of American jurisprudence, and at least on the face, in national legislative policies.