Boulders provide clues on human migration to the Americas

How did early humans first enter the Americas? After crossing into Alaska, the Ice Age adventurers may have trekked along two routes: either by foot through the interior of present day Canada through a grassy passageway between two large ice sheets, or they moved south along the Pacific Coast. Scientists have debated the two theories, and support for the coastal route has grown from archaeological finds, such as 13,000 year old footprints on an island in British Columbia. “We’re not definitively saying they took the coastal route,” said Alia Lesnek, a graduate student at the University at Buffalo and lead author of the study. “We have some of the first direct evidence that that was something that could be done.” The finding, published in the journal ‘Science Advances’, supports the theory that the first people to populate the Americas were seafarers travelling from island to island. After analysing a large gray boulder Lesnek spotted in a grassy valley in southeastern Alaska, the team concluded the islands had been covered by ice sheets up until about 15,000 to 17,000 years ago. The finding suggests that the glaciers covering that part of the Pacific Coast melted and possibly created a pathway for humans.