Boulders Offer New Clues on Human Migration to the Americas

University at Buffalo doctoral candidate Alia Lesnek works at Suemez Island. (Jason Briner)

(CN) – New evidence goes a long way to debunking the longstanding theory of when and how people first came to the Americas.

For years, scientists have posited that humans originally arrived in the Americas via Siberia, journeying across the ancient Bering land bridge on foot and trekking through Canada after an ice-free corridor opened up between immense ice sheets toward the end of the last ice age.

In a study published Wednesday in the journal Science Advances, researchers present findings that support a new, popular theory that the first Americans entered the continent via a coastal route along Alaska’s Pacific border.

“Our study provides some of the first geologic evidence that a coastal migration route was available for early humans as they colonized the new world,” said first author Alia Lesnek, a doctoral candidate at the University of Buffalo. “There was a coastal route available, and the appearance of this newly ice-free terrain may have spurred early humans to migrate southward.”

By analyzing boulders and rocks, the team shows that a portion of a coastal migration route became accessible to humans roughly 17,000 years ago. During this stretch, ancient glaciers receded, exposing islands of southern Alaska’s Alexander Archipelago to sun, air, and potentially human migration.

The timing of these events is critical, as recent archaeological and genetic estimates suggests that humans may have begun journeying deeper into the Americas about 16,000 years ago, shortly after the coastal gateway opened up.

“People are fascinated by these questions of where they come from and how they got there,” said lead scientist Jason Briner, a professor of geology at the University of Buffalo. “Our research contributes to the debate about how humans came to the Americas. It’s potentially adding to what we know about our ancestry and how we colonized our planet.”

The findings do not confirm that early settlers trekked across Alaska’s southern coast to enter the Americas, as the team only examined one section of the coast. Researchers would have to analyze multiple locations along the coastline to draw firmer conclusions.

However, the research is intriguing as it supports the seafaring theory of migration.

The bones of an ancient ringed seal previously discovered in a nearby cave by other scientists also offered relevant clues. The fossils indicate the area was capable of supporting human life as early settlers may have been passing through, according to Briner.

An analysis revealed that the seal bones are roughly 17,000 years old. This suggests the region was ecologically vibrant soon after the ice receded, with resources becoming available for migrating humans.

The findings add to recent evidence contradicting the conventional view that humans settled in North America by traversing an inland route through Canada. This would have required humans to walk through a narrow, ice-free strip of terrain that appeared when two major ice sheets began to separate.

Modern research suggests that while this path may have opened up more than 14,000 years ago, it did not develop enough biological diversity to support human life until about 3,000 years later, Briner said.

This contradicts archaeological findings that indicate humans were already living in Chile at least 15,000 years ago, and in Florida roughly 14,500 years ago.

The new theory offers an alternative story, and the study may signify a step toward solving the mystery of how humans entered the Americas.

“Where we looked at it, the coastal route was not only open – it opened at just the right time,” said co-author Charlotte Lindqvist, an associate professor of biological sciences at the University of Buffalo. “The timing coincides almost exactly with the time in human history that the migration into the Americas is thought to have occurred.”

The study was funded by a University of Buffalo IMPACT award. Lesnek’s work on the project was supported by the National Science Foundation.


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