As the Ice Age began to wane, people from northeastern Asia spread to the Americas, some of the last uninhabited continents on Earth. The pioneers traveled south of mile-high ice sheets covering Canada and found vast lands, abounding with mammoth, giant sloth and other now-extinct megafauna.
This much has been known for decades. But when it comes to the details, debates have raged over precisely when and how humans populated the New World. Today, the story is beginning to take shape, thanks to well-dated archaeological sites, DNA analysis and geological work to understand when ice and sea levels permitted entry to the Americas. It’s clear that people occupied the continents by about 15,000 years ago, probably taking a route along the Pacific coast.
