Peopling of the Americas

The peopling of the Americas began when Paleolithic hunter-gatherers (Paleo-Indians) entered North America from the North Asian Mammoth steppe via the Beringia land bridge, which had formed between northeastern Siberia and western Alaska due to the lowering of sea level during the Last Glacial Maximum (26,000 to 19,000 years ago).^[2] These populations expanded south of the Laurentide Ice Sheet and spread rapidly southward, occupying both North and South America by 12,000 to 14,000 years ago.^{[3][4][5][6][7]} The earliest populations in the Americas, before roughly 10,000 years ago, are known as Paleo-Indians. Indigenous peoples of the Americas have been linked to Siberian populations by proposed linguistic factors, the distribution of blood types, and in genetic composition as reflected by molecular data, such as DNA.^[8][9]

While there is general agreement that the Americas were first settled from Asia, the pattern of migration and the place(s) of origin in Eurasia of the peoples who migrated to the Americas remain unclear.^[4] The traditional theory is that Ancient Beringians moved when sea levels were significantly lowered due to the Quaternary glaciation,^[10][11] following herds of now-extinct Pleistocene megafauna along ice-free corridors that stretched between the Laurentide and Cordilleran ice sheets.^[12] Another route proposed is that, either on foot or using boats, they migrated down the Pacific coast to South America as far as Chile.^[13] Any archaeological evidence of coastal occupation during the last Ice Age would now have been covered by the sea level rise, up to a hundred metres since then.^[14]

The precise date for the peopling of the Americas is a long-standing open question. While advances in archaeology, Pleistocene geology, physical anthropology, and DNA analysis have progressively shed more light on the subject, significant questions remain unresolved.^[15][16] The "Clovis first theory" refers to the hypothesis that the Clovis culture represents the earliest human presence in the Americas about 13,000 years ago.^[17] Evidence of pre-Clovis cultures has accumulated and pushed back the possible date of the first peopling of the Americas.^{[18][19][20][21]} Academics generally believe that humans reached North America south of the Laurentide Ice Sheet at some point between 15,000 and 20,000 years ago.^{[15][18][22][23][24][25]} Some new controversial archaeological evidence suggests the possibility that human arrival in the Americas may have occurred prior to the Last Glacial Maximum more than 20,000 years ago.^{[18][26][27][28][29][30]}