Polynesia of the plant in the Cook Islands have been radiocarbon-dated to 1000, and current thinking is that it was brought to central Polynesia c. 700 and spread across Polynesia from there, possibly by Polynesians who had traveled to South America and back. Thor Heyerdahl proposed in the mid-20th century that the Polynesians had migrated from the northwest coast of Canada by large whale-hunting dugouts, and from South America on balsa-log boats. Many anthropologists have criticised Heyerdahl's theory, including Wade Davis in his book "The Wayfinders". Davis says that Heyerdahl "ignored the overwhelming body of linguistic, ethnographic, and ethnobotanical evidence, augmented
Thor Heyerdahl with steps like those in Peru. But all over Polynesia, Heyerdahl found indications that Tiki's peaceable race had not been able to hold the islands alone for long. He found evidence that suggested that seagoing war canoes as large as Viking ships and lashed together two and two had brought Stone Age Northwest American Indians to Polynesia around 1100 , and they mingled with Tiki's people. The oral history of the people of Easter Island, at least as it was documented by Heyerdahl, is completely consistent with this theory, as is the archaeological record he examined (Heyerdahl 1958). In particular,