Peopling of the Americas

It is believed that the peopling of the Americas began when Paleolithichunter-gatherers (Paleo-Indians) entered North America from the North AsianMammoth 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). These populations expanded south of the Laurentide Ice Sheet, either by sea or land, and spread rapidly southward, occupying both North and South America no later than 14,000 years ago, and possibly before 20,000 years ago. 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 the distribution of blood types, and in genetic composition as reflected by molecular data, such as DNA.

While there is general agreement that the Americas were first settled from Asia, the migration patterns and the place(s) of origin in Eurasia of the peoples who migrated to the Americas remain unclear. The most generally accepted theory is that Ancient Beringians moved when sea levels were significantly lowered due to the Quaternary glaciation, following herds of now-extinct Pleistocenemegafauna along ice-free corridors that stretched between the Laurentide and Cordilleran ice sheets. Another proposed route has them migrating down the Pacific coast to South America as far as Chile, either on foot or using boats. 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 meters since then.

The precise date for the peopling of the Americas is a long-standing open question. While advances in archaeology, Pleistocenegeology, physical anthropology, and DNA analysis have progressively shed more light on the subject, significant questions remain unresolved. 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. Evidence of pre-Clovis cultures has accumulated and pushed back the possible date of the first peopling of the Americas. 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. Current debates center around four glacial-age openings which could have allowed entry into North America: coastal around 24,000 and 15,000 years ago, inland around 14,000 years ago, and coastal around 12,000 years ago. The Swan Point Archaeological Site located in Alaska has yielded the oldest evidence of human habitation that is not disputed, with artifacts that have radiocarbon dates of 14,000 years, indicating the site was occupied around 12,000 BCE.