Ice and ocean constraints on early human migrations into North America along the Pacific Coast
Founding populations of the first Americans likely occupied parts of Beringia during the Last Glacial Maximum (LGM). The timing, pathways, and modes of their southward transit remain unknown, but blockage of the interior route by North American ice sheets between ~26 and 14 cal kyr BP (ka) favors a coastal route during this period. Using models and paleoceanographic data from the North Pacific, we identify climatically favorable intervals when humans could have plausibly traversed the Cordilleran coastal corridor during the terminal Pleistocene. Model simulations suggest that northward coastal currents strengthened during the LGM and at times of enhanced freshwater input, making southward transit by boat more difficult. Repeated Cordilleran glacial-calving events would have further challenged coastal transit on land and at sea. Following these events, ice-free coastal areas opened and seasonal sea ice was present along the Alaskan margin until at least 15 ka. Given evidence for humans south of the ice sheets by 16 ka and possibly earlier, we posit that early people may have taken advantage of winter sea ice that connected islands and coastal refugia. Marine ice-edge habitats offer a rich food supply and traversing coastal sea ice could have mitigated the difficulty of traveling southward in watercraft or on land over glaciers. We identify 24.5 to 22 ka and 16.4 to 14.8 ka as environmentally favorable time periods for coastal migration, when climate conditions provided both winter sea ice and ice-free summer conditions that facilitated year-round marine resource diversity and multiple modes of mobility along the North Pacific coast.
Citation Information
| Publication Year | 2023 |
|---|---|
| Title | Ice and ocean constraints on early human migrations into North America along the Pacific Coast |
| DOI | 10.1073/pnas.2208738120 |
| Authors | Summer K. Praetorius, Jay R. Alder, Alan Condron, Alan Mix, Maureen Walczak, Beth Elaine Caissie, Jon Erlandson |
| Publication Type | Article |
| Publication Subtype | Journal Article |
| Series Title | Proceedings of the National Academy of Sciences |
| Index ID | 70241253 |
| Record Source | USGS Publications Warehouse |
| USGS Organization | Geology, Minerals, Energy, and Geophysics Science Center; Geosciences and Environmental Change Science Center |
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Data release for Ice and ocean constraints on early human migrations into North America along the Pacific coast
Summer Praetorius, PhD
Research Geologist
Jay Alder
Research Physical Scientist
Beth E. Caissie, PhD
Physical Scientist
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Data release for Ice and ocean constraints on early human migrations into North America along the Pacific coast
Founding populations of the first Americans likely occupied parts of Beringia during the Last Glacial Maximum (LGM) (1). The timing, pathways, and modes of their southward transit remain unknown, but blockage of the interior route by North American ice sheets between ~26-14 cal kyr BP (ka) favors a coastal route during this period. Using models and paleoceanographic data from the North Pacific, we - Connect
Summer Praetorius, PhD
Research GeologistEmailPhoneJay Alder
Research Physical ScientistEmailPhoneBeth E. Caissie, PhD
Physical ScientistEmailPhone