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Scientists have been pondering two possible routes for decades. One crawls along the Pacific Coast, weaving between the islands of southern Alaska; the other slips between two giant ice sheets, much further east and inland. In order to help figure out how plausible the first route is, a team of scientists wanted to measure how long ago ice sheets retreated from the coastline—and now they've done just that, as they report in a new paper published in the journal Science Advances. The new research suggests the route would have been accessible about 17,000 years ago.
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