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 then arrived in British Columbia. Heyerdahl called contemporary tribes of British Columbia, such as the Tlingit and Haida, descendants of these migrants. Heyerdahl claimed that cultural and physical similarities existed between these British Columbian tribes, Polynesians, and the Old World source. Heyerdahl's claims aside, however, there is no evidence that the Tlingit, Haida or other British Columbian tribes have an affinity with Polynesians. Heyerdahl's theory of Polynesian origins has not gained acceptance among anthropologists. Physical and cultural evidence had long suggested that Polynesia was settled from west to east, migration having begun from the Asian mainland, not South America. In