A growing number of archaeological and genetic finds are fueling debates on when humans first arrived in North America.

New research presented Dec. 15 at the American Geophysical Union Annual Meeting (AGU23) in San Francisco highlighted “one of the hottest debates in archaeology,” an article by Liza Lester of American Geophysical Union said. 

According to Lester, archaeologists have traditionally argued that people migrated by walking through an ice-free corridor that briefly opened between ice sheets an estimated 13,000 years ago.

But some of the recent finds suggest that people made their way onto the continent much earlier. The discovery of human footprints in New Mexico, which were dated to around 23,000- years-old, is just one example, and Archaeologists have found evidence of coastal settlements in western Canada dating from as early as 14,000-years-ago. 

'Incredible':Oldest known human footprints in North America discovered at national park

The 'kelp highway' theory

The research presented at the AGU23 meeting provides another clue on the origins of North American human migration. 

“Given that the ice-free corridor wouldn't be open for thousands of years before these early arrivals, scientists instead proposed that people may have moved along a ‘kelp highway,’" Lester writes. “This theory holds that early Americans slowly traveled down into North America in boats, following the bountiful goods found in coastal waters.” 

According to Lester, Paleozoic Era climate reconstructions of the Pacific Northwest hint that sea ice may have been one way for people to move farther south along the Pacific coastline from Beringia, “the land bridge between Asia and North America that emerged during the last glacial maximum when ice sheets bound up large amounts of water causing sea levels to fall,”  Lester writes. 

What if they didn't use boats?

Additionally, researchers 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, meaning it would be incredibly difficult to travel along the coast by boat in these conditions, said Summer Praetorius of the U.S. Geological Survey, who presented her team’s work at the summit.

But what if early migrants didn't use boats?

Praetorius' team is asking this very question because evidence shows that people were well adapted to cold environments. If they couldn't paddle against the current, "maybe they were using the sea ice as a platform," Praetorius said.

Praetorius and her colleagues used data that came from tiny, fossilized plankton to map out climate models and “get a fuller picture of ocean conditions during these crucial windows of human migration.”