Hitching a ride on a container ship

National Geographic Explorer Paul Salopek is tracing the path of human migration on foot. But how to cross from one hemisphere to the other? Ancient humans walked across a land bridge between Russia and Alaska, which no longer exists. So, Salopek had to cross the ocean on a commercial shipping container ship. He tells Host Carolyn Beeler about life on the high seas, and the influence geopolitics have had on his walking route.