• University at Buffalo PhD candidate Alia Lesnek at a sampling site on Suemez Island. Photo: Jason Briner

    University at Buffalo PhD candidate Alia Lesnek at a sampling site on Suemez Island, Alaska. (Photo: Jason Briner)

A team of researchers from the University at Buffalo has unlocked a new theory about the first human migration to the Americas: it might not have happened on foot after all.

Archeologists have long argued that humans first crossed to the Americas through an ice-free land corridor spanning the Bering Strait as early as 16,000 years ago. But the Buffalo study, published last month in the journal Science Advances, suggests that a waterway between Eurasia and North America was free of ice a thousand years before that, providing an opportunity for voyages by water.

The researchers initially set out to produce a more complete history of prehistoric ice sheets around northern British Columbia and southeastern Alaska.

“If you look at how big the ice sheets were, when they were that big, and the pattern of how they shrank at the close of the last Ice Age, you’ll notice that there’s a huge data gap,” says Jason Briner, a geologist and one of the study’s lead authors. “We tried to produce some data to fill that gap.”

Landscape of southeastern Alaska

Forests blanket the landscape of southeastern Alaska, so finding areas where bedrock was completely exposed was difficult, the researchers say. (Photo: Jason Briner)
 
Armed with rock saws, hammers and chisels, the researchers collected samples from four islands in southeastern Alaska.

Back at the Buffalo lab, the team used surface exposure dating to determine the age of the rocks.

“Much in the way that the skin on your arms gets a suntan, the Earth’s crust surface gets a ‘tan’ as a function of time,” explains Briner.

When exposed to the sun and the air, an isotope called beryllium-10 accumulates on the rock’s surface. By measuring the concentration of accumulated beryllium-10, researchers are able to estimate how long the rock has been exposed, and therefore how long ago the ice retreated.

The age of the exposed rocks and animal bones previously excavated from the Shuká Káa cave on Prince of Wales Island led the team to their major conclusion: that the earlier retreat of the ice sheet would potentially have allowed humans to travel along that stretch of coast, hunting seals for sustenance. “Although we didn’t find direct evidence that people definitely went through there, we did the beginning work on the ice sheet history to suggest that that door might have opened just in time for people to migrate through the area,” says Briner.

Study lead author Alia Lesnek hopes their work will be a stepping stone to more research about the history of ice sheets in southeastern Alaska and how they could have facilitated a coastal migration.

“What was really missing from the discussion about this was how feasible a coastal migration would have been,” she says. “I think our study is a step towards showing that the coastal migration route was a possible path for people to take to the Americas.”