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
Kon-Tiki expedition sailed roughly west carried along on the Humboldt Current. The crew's first sight of land was the atoll of Puka-Puka on July 30. On August 4, the 97th day after departure, "Kon-Tiki" reached the Angatau atoll. The crew made brief contact with the inhabitants of Angatau Island, but were unable to land safely. Calculations made by Heyerdahl before the trip had indicated that 97 days was the minimum amount of time required to reach the Tuamotu islands, so the encounter with Angatau showed that they had made good time. On August 7, the voyage came to an end when the