While the phrase "pre-Columbian era" literally refers only to the time preceding Christopher Columbus's voyages of 1492, in practice the phrase is usually used to denote the entire history of indigenous Americas cultures until those cultures were exterminated, diminished, or extensively altered by Europeans, even if this happened decades or centuries after Columbus's first landing. For this reason the alternative terms of Precontact Americas, Pre-Colonial Americas or Prehistoric Americas are also in use. In areas of Latin America the term usually used is Pre-Hispanic.
Many pre-Columbian civilizations established hallmarks which included permanent settlements, cities, agriculture, civic and monumental architecture, major earthworks, and complex societal hierarchies. Some of these civilizations had long faded by the time of the first permanent European colonies and the arrival of enslaved Africans (c. late 16th–early 17th centuries), and are known only through archaeological investigations and oral history. Other civilizations were contemporary with the colonial period and were described in European historical accounts of the time. A few, such as the Maya civilization, had their own written records. Because many Christian Europeans of the time viewed such texts as heretical, men like Diego de Landa destroyed many texts in pyres, even while seeking to preserve native histories. Only a few hidden documents have survived in their original languages, while others were transcribed or dictated into Spanish, giving modern historians glimpses of ancient culture and knowledge.
Indigenous American cultures continue to evolve after the pre-Columbian era. Many of these peoples and their descendants continue traditional practices while evolving and adapting new cultural practices and technologies into their lives.
Before the development of archaeology in the 19th century, historians of the pre-Columbian period mainly interpreted the records of the European conquerors and the accounts of early European travelers and antiquaries. It was not until the nineteenth century that the work of men such as John Lloyd Stephens, Eduard Seler and Alfred P. Maudslay, and of institutions such as the Peabody Museum of Archaeology and Ethnology of Harvard University, led to the reconsideration and criticism of the European sources. Now, the scholarly study of pre-Columbian cultures is most often based on scientific and multidisciplinary methodologies.
Asian nomads are thought to have entered the Americas via the Bering Land Bridge (Beringia), now the Bering Strait and possibly along the coast. Genetic evidence found in Amerindians' maternally inherited mitochondrial DNA (mtDNA) supports the theory of multiple genetic populations migrating from Asia. Over the course of millennia, Paleo-Indians spread throughout North and South America. Exactly when the first group of people migrated into the Americas is the subject of much debate. One of the earliest identifiable cultures was the Clovis culture, with sites dating from some 13,000 years ago. However, older sites dating back to 20,000 years ago have been claimed. Some genetic studies estimate the colonization of the Americas dates from between 40,000 and 13,000 years ago. The chronology of migration models is currently divided into two general approaches. The first is the short chronology theory with the first movement beyond Alaska into the New World occurring no earlier than 14,000–17,000 years ago, followed by successive waves of immigrants. The second belief is the long chronology theory, which proposes that the first group of people entered the hemisphere at a much earlier date, possibly 50,000–40,000 years ago or earlier.
Artifacts have been found in both North and South America which have been dated to 14,000 years ago, and accordingly humans have been proposed to have reached Cape Horn at the southern tip of South America by this time. In that case, the Eskimo peoples would have arrived separately and at a much later date, probably no more than 2,000 years ago, moving across the ice from Siberia into Alaska.
The North American climate was unstable as the ice age receded. It finally stabilized by about 10,000 years ago; climatic conditions were then very similar to today's. Within this time frame, roughly pertaining to the Archaic Period, numerous archaeological cultures have been identified.