Peopling of the Americas

Available scientific evidence indicates that modern humans emerged from Africa over 100,000 years ago, yet did not arrive in the Americas until less than 20,000 years ago. Current understanding of the settlement of the Americas derives from advances in four interrelated disciplines: archaeology, geology, physical anthropology, and DNA analysis. 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. In the 2000s, researchers sought to use familiar tools to validate or reject established theories, such as Clovis first. The archeological evidence suggests that the Paleo-Indians' first dispersal into the Americas occurred near the end of the last glacial period or, more specifically, what is known as the Last Glacial Maximum (LGM), around 16,500–13,000 years ago.

The settlement of the Americas is of intense interest to archaeologists and anthropologists. Modern biochemical techniques, as well as the accumulation of archaeological and geological evidence, have shed progressively more light on the subject; however, significant questions remain unresolved.

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 the eustatic sea level. The variation of the eustatic sea level with 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, caused the revealing of Beringia as 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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