Tracing the First North American Settlers: The Role of the Sea Ice Route

by Liam O'Connor
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Early Human Migration

Recent discoveries indicate that the first human settlers might have reached North America before 13,000 years ago, potentially navigating a “sea ice route” along the Pacific Coast. This hypothesis, bolstered by paleoclimatic evidence, questions the conventional beliefs about migration and highlights the versatility of early humans. Source:

New studies propose that early inhabitants of the Americas might have used the winter sea ice from Beringia as a migration path as early as 24,000 years ago.

A major topic of debate in archaeology is the timing and method of the initial human arrival in North America. The prevailing theory has been that early humans migrated through a temporarily ice-free corridor between glaciers around 13,000 years ago.

Revisiting Migration Theories with New Findings

However, recent archaeological and genetic discoveries, such as human footprints in New Mexico dating back to about 23,000 years, suggest an earlier arrival. These first settlers likely followed the Pacific coastline from Beringia, a land bridge that appeared during the last glacial maximum when sea levels dropped due to ice formation.

At the American Geophysical Union Annual Meeting (AGU23) in San Francisco on December 15, new paleoclimate studies of the Pacific Northwest indicated that sea ice could have facilitated southward migration.

Rethinking Coastal Migration Theories

The concept of early settlers traveling along the Pacific Coast is not novel. It is believed that people were already south of the large glaciers covering the continent by at least 16,000 years ago. Since the ice-free corridor would not open for several thousand years, scientists proposed an alternative route involving a “kelp highway” where early settlers gradually moved into North America by boat, following the rich resources along the coast.

Archaeological evidence of coastal settlements in western Canada dates back to around 14,000 years ago. Research in 2020 suggested that freshwater from melting glaciers created strong currents, posing challenges for coastal navigation.

Sea Ice in Nunavut, Canada. Courtesy of Grid-Arendel CC-BY-NC-SA

Navigating Treacherous Waters via Ice

To understand ocean conditions during key periods of human migration, Summer Praetorius and her colleagues from the US Geological Survey analyzed climate indicators in ocean sediments, including data from tiny fossilized plankton, which help reconstruct past ocean temperatures, salinity, and sea ice coverage.

Praetorius’ research, presented at AGU23, focused on the climate history and geology of Beringia and the North Pacific during the Pleistocene. The conference drew 24,000 experts from various Earth and space science fields and had 3,000 online participants.

Her team used climate models to determine that ocean currents were significantly stronger during the last glacial maximum, about 20,000 years ago, making boat travel challenging. However, their findings also indicated that the region had winter sea ice until about 15,000 years ago. Praetorius suggested that early humans, adapted to cold conditions, may have used the sea ice as a platform for movement and hunting marine mammals.

Utilizing Sea Ice for Migration

Like Arctic inhabitants today who travel on sea ice using dog sleds and snowmobiles, early Americans might have similarly used the ‘sea ice highway’ to traverse and gradually populate North America. The climate data indicates that migration along the coastal route could have been feasible between 24,500-22,000 years ago and 16,400-14,800 years ago, assisted by winter sea ice.

Combining Historical and New Perspectives

While confirming sea ice usage for migration is challenging due to submerged archaeological sites, this theory offers a fresh perspective on how humans could have reached North America without a land bridge or straightforward sea passage.

The sea ice route theory does not exclude subsequent human migrations. By 14,000 years ago, the Alaskan current had weakened, facilitating boat travel along the coast.

“Nothing is off the table,” Praetorius remarked. “We are continually amazed by ancient human resourcefulness.”

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