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
William Willis (sailor) effect Bernard Carnot's escape, which he eventually accomplished. During his first solo expedition in 1954 from South America to American Samoa, he sailed 6,700 miles – 2,200 miles farther than did Thor Heyerdahl on Kon-Tiki. His raft was named "Seven Little Sisters" and was crewed by himself, his parrot, and cat. Willis was age 61 at the time of this voyage. In a second great voyage ten years later, at the age of 71, he sailed 10,000 miles from South America to Australia single-handing a 34-foot (10.4 m) raft named "Age Unlimited". He left Callao on 5 July 1963, made