The narrative of early human migration takes an unexpected turn with revelations about a possible ‘sea ice highway’ to North America. As presented at AGU23, this groundbreaking theory sheds light on the resourcefulness of ancient explorers navigating challenging coastal waters.

New research challenges established theories on the arrival of North America’s first inhabitants.

Presented at AGU23, findings suggest that some early Americans may have ventured along a ‘sea ice highway’ over dangerous waters, reshaping our understanding of ancient migration routes and highlighting the resilience of early human explorers in the face of challenging conditions.

The method and timing of human arrival in North America have long been debated in archaeology. Traditional theories propose a land route through an ice-free corridor that temporarily opened between ice sheets around 13,000 years ago. However, growing archaeological and genetic evidence, such as 23,000-year-old human footprints in New Mexico, points to an earlier migration.

These early Americans likely traveled down the Pacific coastline from Beringia, the land bridge between Asia and North America that emerged during the last glacial maximum, lowering sea levels.

New research, presented at the American Geophysical Union Annual Meeting, explores paleoclimate reconstructions in the Pacific Northwest, suggesting that sea ice might have been a viable route for southerly migration.

The notion of early Americans traveling along the Pacific Coast is not entirely new, with evidence suggesting human presence south of massive ice sheets by at least 16,000 years ago.

Given that the ice-free corridor would not open for several thousand years after their arrival, the concept of a “kelp highway” emerged, proposing that early Americans slowly migrated into North America by boat, following coastal resources.

Archaeologists have discovered coastal settlements in western Canada dating back to around 14,000 years ago. However, concerns were raised in 2020 about the difficulty of coastal travel due to strong currents resulting from melting glaciers at that time.

To understand ocean conditions during crucial migration periods, researchers examined climate proxies in coastal sediment, primarily fossilized plankton, using climate models.

Their findings indicate that ocean currents were over twice as strong during the last glacial maximum around 20,000 years ago, making boat travel challenging.

However, the region had winter sea ice until approximately 15,000 years ago, suggesting the possibility of using it as a platform for travel.

As cold-adapted individuals, early Americans might have navigated the “sea ice highway,” similar to contemporary Arctic communities using dog sleds and snowmobiles. Climate data propose favorable conditions for migration between 24,500-22,000 years ago and 16,400-14,800 years ago, potentially assisted by winter sea ice.

While confirming sea ice usage is challenging due to underwater archaeological sites, this concept offers a new perspective on how humans might have reached North America without a land bridge or easy ocean travel.

Additionally, the sea ice highway does not preclude other migration routes, as conditions for coastal boat travel improved around 14,000 years ago.

In the words of Summer Praetorius, lead researcher, “Nothing is off the table. We will always be surprised by ancient human ingenuity.”

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