**Peopling of the Americas:**
– Paleo-Indians entered North America from the North Asian Mammoth steppe via the Beringia land bridge.
– Indigenous peoples of the Americas have been linked to Siberian populations by linguistic factors and genetic composition.
– Evidence suggests human arrival in the Americas may have occurred prior to the Last Glacial Maximum more than 20,000 years ago.
– The precise date for the peopling of the Americas remains a long-standing open question.
– Indigenous populations expanded south of the Laurentide Ice Sheet and occupied both North and South America by 12,000 to 14,000 years ago.
**Environmental Changes and Beringia:**
– The Earth’s ocean water was stored in glacier ice during the Wisconsin glaciation.
– A drop in sea level around 30,000 years BP created Beringia, connecting Siberia with Alaska.
– The Beringian land bridge was submerged after the Last Glacial Maximum.
– Estimates place the final re-submergence of the land bridge around 11,000 years BP.
– Research on Beringian paleogeography during deglaciation could change estimates of the land bridge’s submergence.
**Glaciers and Climate:**
– The Last Glacial Maximum saw the expansion of alpine glaciers and continental ice sheets.
– Coastal alpine glaciers and Cordilleran ice sheets isolated Beringia from the Pacific coast.
– Climates in eastern Siberia fluctuated between present-day conditions and colder periods.
– Coastal environments were exposed due to lowered sea levels.
– The ice-free corridor to the interior of North America opened between 13,000 and 12,000 BP.
**Chronology and Migration Theories:**
– Archaeological presence in the Americas dates back to 15,000 years ago.
– Models are divided into short and long chronology theories.
– Challenges to the Clovis First theory emerged in the 2000s.
– Evidence for pre-LGM human presence includes sites like Old Crow Flats in Alaska.
– Coastal migration is proposed as an alternative hypothesis to the ice-free corridor theory.
**Genetic Studies and Physical Anthropology:**
– Genetic studies reconstruct the development of Native American DNA haplogroups.
– Mitochondrial (mtDNA) lineages like A, B, C, D, and X are common in eastern Asian and Native American populations.
– Physical anthropology studies show distinct craniofacial traits in Paleo-Indian skeletons.
– HTLV-1 genomics suggest a connection between subtypes found in the Americas and Ainu ancestors.
– Luzia Woman’s DNA sequencing contradicts the initial interpretation of her ancestry.
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). 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. 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 linguistic factors, 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 pattern of migration and the place(s) of origin in Eurasia of the peoples who migrated to the Americas remain unclear. The traditional theory is that Ancient Beringians moved when sea levels were significantly lowered due to the Quaternary glaciation, following 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 coast to South America as far as Chile. 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.
The precise date for the peopling of the Americas is a long-standing open question, and while advances in archaeology, Pleistocene geology, 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. 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.