Praetorious' team used climate models and found that ocean currents were more than twice the strength they are today during the height of the last glacial maximum around 20,000 years ago due to glacial winds and lower sea levels. While not impossible, to paddle against, these conditions would have made traveling by boat very difficult, Praetorius said.
However, the records also showed that much of the area was home to winter sea ice until around 15,000 years ago. As a cold-adapted people, "rather than having to paddle against this horrible glacial current, maybe they were using the sea ice as a platform," Praetorius said.
Arctic people today travel along sea ice on dog sleds and snow mobiles. Early Americans may also have used the 'sea ice highway' to get around and hunt marine mammals, slowly making their way into North America in the process, Praetorius said. The climate data suggest conditions along the coastal route may have been conducive to migration between 24,500-22,000 years ago and 16,400-14,800 years ago, possibly aided by the presence of winter sea ice.
While proving that people were using sea ice to travel will be tricky given most of the archeological sites are underwater, the theory provides a new framework for understanding how humans may have arrived in North America without a land bridge or easy ocean travel.
And the sea ice highway isn't mutually exclusive with other human migrations further down the line, says Praetorius. The team's models show , the Alaskan current had calmed down by 14,000 years ago, making it easier for people to travel by boat along the coast.
"Nothing is off the table," she said. "We will always be surprised by ancient human ingenuity."
