Always wondered why this is such a surprise. Getting around the planet, especially over very long time periods, is just not that hard. We're stuck in a mentality that says long distance travel was impossible prior to Columbus. But realize he was just the guy who traveled and came BACK. To migrate over long distances you don't by definition need to return, so the people you left have no idea where you went. Also you have to have a motivation to tell people where you went. Supposedly there had been fishing expeditions to the new world coast for a long time prior to Columbus. The fishermen didn't want anyone to know where they were finding such good fishing grounds so never told where they had traveled.
In addition, the evidence points to a major impact around 12.5kybp centered around the northern plains. This would have destroyed most of the evidence of any human presence.
In addition, the evidence points to a major impact around 12.5kybp centered around the northern plains. This would have destroyed most of the evidence of any human presence.