Is the world closing its doors?

Migration is as old as humanity itself. In today's world, it ebbs and flows as nations change their border policies with the times. National Geographic Explorer Paul Salopek has been retracing the global path of the earliest humans on foot for the past 13 years. In that time, he has witnessed a lot of migration in real time. He joins Host Marco Werman to share his observations on how migration's role in the global zeitgeist has changed.