The sweet potato, Ipomoea batatas, is in terms of worldwide distribution the most important of all tropical root crops. Indeed, it is the seventh largest of all food crops. Eighty percent of world production is in China.
I. batatas is indigenous to Andean South America. Evidence for it goes back to 8000 B.C. in a Peruvian cave. It spread across the Pacific to Polynesia before Columbus, perhaps on a raft of the sort Thor Heyerdahl built and successfully piloted on the same route in 1947. Linguistic evidence for this is just as persuasive. Davidson points to obvious similarities between the ancient Peruvian kumar and kumala, gumala, umala, words for sweet potato in various Oceanic tongues.