The Americas were the last (well, second-to-last if you count Antarctica) continents to be inhabited by early humans. Archaeologists estimate that people entered North America by crossing over the Bering Strait, which back then was a wide swath of land, about 15,000 years ago.

But what compels people to walk that fast and that far into the unknown? The most obvious reason is that one has to pack up and go because things are not so good at home. Long ago, that probably meant that the climate had changed and made life impossible.

Or maybe, they came because they could. Humans seem to have a universal penchant for moving round.