New research results show that early humans arrived in North America as early as 13,000 years ago, possibly taking advantage of the "sea ice highway" along the Pacific coast. This theory, supported by paleoclimate data, challenges traditional migration theories and highlights the adaptability of early humans.
New research suggests that some early Americans may have been traveling on winter sea ice along the coast from Beringia as early as 24,000 years ago.
One of the hottest debates in archaeology is how and when humans first arrived in North America. Archaeologists have long believed that humans arrived here about 13,000 years ago through a briefly open ice-free corridor between ice sheets.
New evidence challenges traditional theory
But a growing number of archaeological and genetic discoveries - including the discovery of human footprints in New Mexico dating back about 23,000 years ago - suggest that humans arrived in the Americas much earlier. These early Americans likely traveled along the Pacific coastline from Beringia, the land bridge connecting Asia and North America.
Now, a paleoclimate reconstruction of the Pacific Northwest suggests sea ice may have been a way for humans to migrate south, according to research presented Friday, Dec. 15, at the American Geophysical Union Annual Meeting (AGU23) in San Francisco.
coastal migration theory
The idea that early Americans may have migrated along the Pacific Coast is not new. At least 16,000 years ago, people were likely south of the vast ice sheets that once covered much of the American continent. Given that the ice-free corridor would not have been open for thousands of years before these early arrivals, scientists have instead proposed that people may have moved along a "kelp highway," where early Americans slowly entered North America by boat following the bounty they found in coastal waters.
Archaeologists have found evidence of coastal settlements in western Canada as early as 14,000 years ago. But in 2020, researchers noticed that fresh water from melting glaciers at that time may have created a strong current that made it difficult for people to travel along the coast.
Crossing dangerous waters
To get a more complete picture of ocean conditions during these critical windows of human migration, Summer Praetorius of the U.S. Geological Survey and her colleagues studied climate proxies in coastal marine sediments. Most of the data comes from tiny plankton fossils. Their abundance and chemical properties help scientists reconstruct ocean temperature, salinity and sea ice coverage.
Pratorius' presentation was part of a session at AGU23 on the climate history and geology of Beringia and the North Pacific during the Pleistocene. This year, the week-long conference brought 24,000 experts from the Earth and space science fields to San Francisco and connected 3,000 online attendees.
Using climate models, Prato Lires' team found that during the last glacial maximum about 20,000 years ago, ocean currents were more than twice as strong as they are today due to glacial winds and lower sea levels. While it's not impossible to travel upstream, Praetorius said the conditions would make traveling by boat very difficult.
However, records also show that much of the region was home to winter sea ice until about 15,000 years ago. As a cold-adapted people, "instead of paddling against the terrifying glacial currents, maybe they would have used the sea ice as a platform," Praetorius said.
Sea ice as a migration path
Today, people in the Arctic travel along the sea ice on dog sleds and snowmobiles. Early Americans may also have used 'sea-ice highways' to roam and hunt marine mammals, slowly entering North America in the process, Pratorius said. Climate data suggests that conditions along the coastal route may have been favorable for migration between 24,500 and 22,000 years ago and between 16,400 and 14,800 years ago, possibly aided by the presence of winter sea ice.
Integrate old and new theories
Proving that humans used sea ice to travel is difficult because most archaeological sites are underwater, but the idea provides a new framework for understanding how humans arrived in North America without land bridges or easy ocean travel.
Praetorius said the Sea-Ice Highway is not mutually exclusive with other more distant human migrations. The team's models show that the Alaskan currents calmed down 14,000 years ago, making it easier for people to travel along the coastline by boat.
"Nothing is impossible," she said. "The ingenuity of ancient humans never ceases to amaze us."
Compiled from: ScitechDaily