North America’s first people may have arrived via ‘sea ice highway’ 24,000 years ago, suggests study

How and when humans reached North America remains a highly debated topic in archaeology, with various theories and studies attempting to unravel the mystery. Now a recent study suggests that sea ice might have played a significant role in facilitating human movement southward.

Traditionally, the prevailing belief among scientists has been that approximately 13,000 years ago, stone age hunters travelled across a land bridge that connects eastern Siberia and western Alaska. Subsequently, they walked through an ice-free corridor that briefly opened between ice sheets during that period.
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However, recent discoveries, such as human footprints in New Mexico dating back to 23,000 years ago, have reignited the debate by proposing an earlier human presence on the continent.
The recent research, presented at the American Geophysical Union Annual Meeting (AGU23) on December 15, puts forward the idea that sea ice may have served as a route for human migration thousands of years ago. Although the notion of early Americans travelling along the Pacific Coast is not new, the conditions were previously considered unfavourable due to strong currents caused by freshwater from melting glaciers in 2020.

In response to these challenges, Summer Praetorius from the United States Geological Survey (USGS) and her team examined climate proxies in ocean sediment from the coast. Utilising data from tiny, fossilised plankton and climate models, they reconstructed ocean temperatures, salinity, and sea ice cover at the time.

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The findings revealed that ocean currents were twice as strong as they are today during the last glacial maximum around 20,000 years ago, making boat travel nearly impossible. Praetorius suggests that people adapted to the cold might have used sea ice as a platform instead of battling the harsh glacial currents. Drawing a parallel with Arctic travel, she proposed that early Americans could have employed a ‘sea ice highway’ to navigate, hunt marine mammals, and gradually make their way into North America.
Although proving this theory is challenging due to many archaeological sites being underwater, it provides a new framework for understanding early human migration. Praetorius also pointed out that the sea ice highway theory does not exclude other later human migrations, as their models indicate that the Alaskan current had become more manageable by 14,000 years ago, allowing for easier coastal travel by boat.