Ancient and historic dispersals of sweet potato in Oceania.

O n his voyages across the Pacific, Captain James Cook encountered geographically disparate Polynesian societies, including those living on Easter Island, Hawai’i, and the north island of New Zealand. These far-flung communities cultivated a South American domesticate, the sweet potato (Ipomoea batatas). Subsequent debates concerning the timing and nature of the dispersals of sweet potato into and across the Pacific have proven contentious, including Thor Heyerdahl’s famous Kon Tiki voyage from South America to Easter Island (1). Archaeological research has now conclusively shown that the sweet potato was introduced to Central Polynesia by approximately A.D. 1200 to 1300 (2), most likely by Polynesian voyagers who reached South America and subsequently spread the crop to the widely dispersed islands of the Polynesian triangle (e.g., ref. 3). Now, Roullier et al. (4) use genetic analyses (chloroplast and nuclear microsatellites) of modern and historically collected herbaria samples to clarify longstanding questions concerning historical dispersals of sweet potato across the Pacific. In sum, their research confirms key aspects of the “tripartite hypothesis” for sweet potato dispersal, with major implications beyond Oceania.