Prehistoric migration and settlement of the Americas from Asia

The continents of North and South America were settled by Upper Paleolithic hunter-gatherers from North Asia between 20,000 and 10,000 years ago, by way of 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. The earliest populations in the Americas, between roughly 20,000 and 10,000 years ago are also known as Paleo-Indians.

Advances in archaeology, geology, physical anthropology, and DNA analysis have shed progressively more light on the subject; however, significant questions remain unresolved. While there is general agreement that the Americas were first settled from Asia, the pattern of migration, its timing, and the place(s) of origin in Asia of the peoples who migrated to the Americas remain unclear. Specifically, "Clovis first" refers to the hypothesis that the Clovis culture represents the earliest human presence in the Americas, beginning about 13,000 years ago; evidence of pre-Clovis cultures has accumulated during the 2000s to 2010s, pushing back the date of the first peopling of the Americas to about 16,000 years, or possibly close to 20,000 years ago.

For an introduction to the radiocarbon dating techniques used by archaeologists and geologists, see radiocarbon dating.

During the Wisconsin Glaciation, varying portions of the Earth's water were stored as glacier ice. As water accumulated in glaciers, the volume of water in the oceans correspondingly decreased, resulting in lowering of global sea level. The variation of sea level over time has been reconstructed using oxygen isotope analysis of deep sea cores, the dating of marine terraces, and high resolution oxygen isotope sampling from ocean basins and modern ice caps. A drop of eustatic sea level by about 60 m to 120 m lower than present-day levels, commencing around 30,000 years BP, created Beringia, a durable and extensive geographic feature connecting Siberia with Alaska. With the rise of sea level after the Last Glacial Maximum (LGM), the Beringian land bridge was again submerged. Estimates of the final re-submergence of the Beringian land bridge based purely on present bathymetry of the Bering Strait and eustatic sea level curve place the event around 11,000 years BP (Figure 1). Ongoing research reconstructing Beringian paleogeography during deglaciation could change that estimate and possible earlier submergence could further constrain models of human migration into North America.

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