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 people whose former battle axes and swords our ancestors condemned. Our planet is bigger than the reed bundles that have carried us across the seas, and yet small enough to run the same risks unless those of us still alive open our eyes and minds to the desperate need of intelligent collaboration to save ourselves and our common civilization from what we are about to convert into a sinking ship. In the years that followed, Heyerdahl was often outspoken on issues of international peace and the environment. The "Tigris" had an eleven-man crew: Thor Heyerdahl (Norway), Norman Baker (USA), Carlo