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 history, consulting what was then the world's largest private collection of books and papers on Polynesia, owned by Bjarne Kroepelien, a wealthy wine merchant in Oslo. (This collection was later purchased by the University of Oslo Library from Kroepelien's heirs and was attached to the Kon-Tiki Museum research department.) After seven terms and consultations with experts in Berlin, a project was developed and sponsored by Heyerdahl's zoology professors, Kristine Bonnevie and Hjalmar Broch. He was to visit some isolated Pacific island groups and study how the local animals had found their way there. Just before sailing together to the Marquesas