A frozen highway may have given ancient travelers a clear path from Siberia into the New World more than 10,000 years earlier than America’s First Nations people are thought to have arrived.
According to data based on studies of sediment and fossilized marine life analyzed by researchers from the US Geological Survey, Woods Hole Oceanographic Institution, and Oregon State University, an early migration would have been made a lot easier by sea ice.
A presentation by US Geological Survey geologist Summer Praetorius delivered at the American Geophysical Union Annual Meeting (AGU23) in San Francisco suggests flat expanses of winter ice may have played a critical role in facilitating travel at times when passage by boat would have been too treacherous.
For the better part of half a century, archaeologists generally regarded a culture known as the Clovis people as the original pioneers of the North American continent. Lured by fertile new hunting grounds, families trekked across lands briefly exposed by retreating ice linking Siberia with Alaska around 13,000 years ago.
The hypothesis had a lot going for it. A handful of skeletal remains and similarly-styled projectile tips found among now-extinct megafauna served as tangible evidence of their existence, while climate-data supported a timeline of relatively easy movement between land masses.
Yet a series of discoveries made over recent decades has continued to erode confidence in the Clovis-first hypothesis, pushing back the arrival of humans in the Americas to as far back as the Last Glacial Maximum more than 25,000 years ago.
One pressing question is how these ancient travelers made the arduous journey in the first place. While sea levels were likely to have been low enough to expose a solid bridge across the top of the world as far back as nearly 36,000 years ago, the rugged cap of snow and glacier covering the landscape would have been a struggle, if traversable at all.
Once glaciers began to retreat, a thin strip of coastal ecosystems could have provided communities with resources and a means of travel by boat. A 14,000-year-old settlement on Canada’s western coast further supports the possibility that pre-Clovis people were inching their way along the water’s edge.
The ‘kelp highway hypothesis’ presumes marine technology was up to the task of safely carrying families thousands of kilometers through a bitter-cold marine environment, a possibility that may have depended largely on when the journey was made.
According to a study published in 2020, windows of opportunity may have closed during critical warm periods, when accelerated melting would have sent currents swirling in the wrong direction for migrating paddlers as floods of freshwater poured into the ocean.
According to Praetorius and her team, an analysis of climate models confirms high winds and lower sea levels would have helped make ocean currents 20,000 years ago twice as strong as they are today, adding to the woes of any would-be mariners.
Yet records also suggest ample expanses of winter sea ice would have been present up until around 15,000 years ago, along which migrants could have walked, or even sledded.
“We identify 24.5 – 22 [thousand years ago] and 16.4 – 14.8 [thousand years ago] as the most likely time periods to accommodate early migration along the Alaskan coast, possibly aided by movement and subsistence on a “Sea-ice Highway”,” the researchers write in their report.
That’s not to say sea travel ought to be ruled out in periods when the currents favored it. Nor is it solid evidence that such journeys did indeed take place.
In light of emerging signs that humans may have ventured as far south as New Mexico more than 20,000 years ago, it can be presumed there may have been a relatively safe and open path their ancestors took to make the almighty leap between worlds.
This research was presented at the American Geophysical Union Annual Meeting in San Francisco, 16 December.
Dr. Thomas Hughes is a UK-based scientist and science communicator who makes complex topics accessible to readers. His articles explore breakthroughs in various scientific disciplines, from space exploration to cutting-edge research.
