Polynesian navigation snow. In the mid-20th century, Thor Heyerdahl proposed a new theory of Polynesian origins (one which did not win general acceptance), arguing that the Polynesians had migrated from South America on balsa-log boats. The presence in the Cook Islands of sweet potato that is a plant native to the Americas (called "kūmara" in Māori), which have been radiocarbon-dated to 1000 CE, has been cited as evidence that Americans could have traveled to Oceania. The current thinking is that sweet potato was brought to central Polynesia circa 700 CE and spread across Polynesia from there, possibly by Polynesians who had traveled
Thor Heyerdahl evidence suggesting contact between South America and Polynesia. The "Kon-Tiki" smashed into the reef at Raroia in the Tuamotus on August 7, 1947, after a 101-day, 4,300-nautical-mile (5,000-mile or 8,000 km) journey across the Pacific Ocean. Heyerdahl had nearly drowned at least twice in childhood and did not take easily to water; he said later that there were times in each of his raft voyages when he feared for his life. "Kon-Tiki" demonstrated that it was possible for a primitive raft to sail the Pacific with relative ease and safety, especially to the west (with the trade winds). The raft