Only on the "CBS This Morning" podcast, sports writer Rob Ruck discusses the dominance of Samoan players in football with "CBS This Morning Saturday" co-host Dana Jacobson. In his new book, "Tropic of Football: The Long and Perilous Journey of Samoans to the NFL," Ruck looks how American territory of Samoa became "a micro-culture of sporting excellence." Playing without fear, he explains why the Polynesian culture has proven to the perfect match for football.