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 Islands in 1936, Heyerdahl married his first wife, Liv Coucheron-Torp (1916–1969), whom he had met shortly before enrolling at the university, and who had studied economics there. The couple had two sons: Thor Jr and Bjørn. The marriage ended in divorce. After the Occupation of Norway by Nazi Germany, he served with the Free Norwegian Forces from 1944, in the far north province of Finnmark. In 1949, Heyerdahl married Yvonne Dedekam-Simonsen (1924–2006). They had three daughters: Annette, Marian and Helene Elisabeth. They were divorced in 1969. Heyerdahl blamed their separation on his being away from home and differences in their