The sweet potato, a food crop native to the Americas, was widespread in Polynesia by the time European explorers first reached the Pacific. Sweet potato has been radiocarbon-dated in the Cook Islands to 1000 CE, and current thinking is that it was brought to central Polynesia c. 700 CE and spread across Polynesia from there. It has been suggested that it was brought by Polynesians who had traveled across the Pacific to South America and back, or that South Americans brought it to Polynesia. It is also possible that the plant floated across the ocean after being discarded from the cargo of a boat. Phylogenetic analysis supports the hypothesis of at least two separate introductions of sweet potatoes from South America into Polynesia, including one before and one after European contact.