New evidence hints that early humans pass an ancient coastal route along Alaska's Pacific Border to settle in the continent and become the first Americans.

A team of scientists led by the University at Buffalo explored four different islands within Alaska's Alexander Archipelago. The team examined boulders and bedrock and concluded that the glacial region melted and had contact with the air and sun some 17,000 years ago.

The estimated timing from the current study coincided with previous genetic and archeological conclusions that early humans started journeying deeper into the Americas some 16,000 years ago. At the time, the coastal road may have opened to accommodate this human migration.

To support this hypothesis, the team also pointed to a previous discovery of the bones of an ancient ringed seal in the same region. The current study estimated the age of the seal bones was about 17,000 years old, suggesting that the ancient coastal route, indeed, was capable of supporting life.

Surface Exposure Dating

To identify the exact timing of when the ice melted for the coastal route to emerge, the team collected rock samples from the islands. They tested these rock samples using a process called surface exposure dating.

The method involved testing the chemicals that accumulated on the surface of the rocks. This chemical composition resulted to the bedrock's sudden exposure to cosmic radiation that came from space. The chemical build up was a reaction to the sudden contact with the sun after being under the ice glaciers for a long time.

The team used the same method to analyze the "erratics" that they found in the region. Erratics are big Earth rocks that glaciers either brought with them or left behind as glaciers continued to melt and break apart.

"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 Alia Lesnek, first author of the study and a geology Ph.D. candidate from UB.

The Debate On Early Human Migration To North America

The more known theory of human migration was that the first Americans came to the continent through Siberia. They marched through the now non-existent Bering Bridge and hiked through Canada where a route opened as the Ice Age neared its final stages and two major ice sheets separated. This route supposedly opened up more than 14,000 years ago and was able to support biological life up until about 13,000 years ago.

Jason Briner, lead scientist, and professor of geology in UB's College of Arts and Sciences highlighted that there appeared to be a loophole about the aforesaid theory as more recent archeological findings suggested that humans already inhabited Chile for more than 15,000 years ago. Briner also highlighted findings that revealed humans were already residing in Florida some 14,500 years ago.

Briner clarified that result of their current study, published in the journal Science Advances, does not offer confirmation yet that early humans journeyed Alaska's Pacific Border into North America. He explained that they need to examine more locations before they could declare firmer conclusions on the matter.

Nevertheless, the discovery strengthened a less known theory of how early people came to America. 

"People are fascinated by these questions of where they come from and how they got there. 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," Briner said.

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