Sweet potatoes hold a mystery. They are native to South America and yet somehow got completely across the Pacific, becoming a staple, long before the Spanish and their galleons. You can imagine the Spaniards surprise on sailing east, their cargo holds filled with fresh and previously unknown foods, like the camote, the sweet potato. Somewhere in the Pacific they entered a harbor and found this strange tuber had beat them there.
But that is just a story. For most of the last century, as scholars have tried to piece together the history of Oceania the sweet potato tantalized them. Initially, though, they could not decide if it came with the Europeans or earlier. Legend argued for earlier, but the tropical soils did not maintain evidence of this soft and perishable food. They just knew it was widespread in Oceania, a major foodstuff, and had a lot of variety, though it seemed to be South American in origin.
The idea of some sort of contact between the high civilizations of the Andes and the master sailors of Polynesia held lots of fascination, though it did not fit the master narrative of Europeans actively sailing the globe and discovering the unknown.
According the the Huarochiri cycle of stories, the creator hero Contiqsi Wiracocha had headed eastward, like the setting sun, from the site of Pachacamac. The Islands of the coast figured in the tale, but to adventurer scholars such as Thor Hyerdahl stories like this and others suggested that maybe such tales enclosed a history of South Americans traveling westward like the sun.
Hyerdahl, who had done fieldwork in the Marquesan Islands, was entranced with this notion and in 1947 built a raft in Peru, called it Kon-Tiki after the Andean hero / god, and sailed west to show such a voyage was possible. Decades later, another Nowegian, Erik Thorsby, of the University of Oslo, found genetic evidence in Easter Islanders that they had mixed with Native Americans well before the Spanish came.
Despite Hyerdahl, the stronger ideas has been one of Polynesians traveling eastward to South America long before Columbus. A collection of chicken bones found in Chile were carbon dated to 1321 and 1407 AD well before Columbus, adding to the debate about the chicken’s origin in South America–did it come with the Spanish or did they find it already there. This collection of bones, when analyzed genetically seem to answer the question. They proved to correspond to Polynesian chickens.
And now the sweet potato. According to an article published in the US last week in the Proceedings of the National Academy of Sciences genetic evidence concludes the sweet potato spread through Oceania in three phases. It did not just come with the Spanish from Mexico or through the Caribbean, it also came directly from South America much earlier.
The evidence is tangled because of much cross breeding among varieties, giving rise to a very diverse set of sweet potatoes in the islands of Oceania.
Researchers Croline Rouillier, Laure Benoit, Doyle B. McKey, and Vincent Lebota looked at markers such as chloroplast and nuclear microsatellites in modern and herbarium samples. Their results strongly suport the hypothesis, they conclude, that Polynesian sweet potatoes left Peru and Ecuador to make their way westward before the Spanish.
The sweet potato certainly changed historic Oceania by providing what became an important foodstuff, though the eyes of historians were not looking, unlike what later happened with the potato in Ireland. This tropical tuber, that is still very important in Andean cuisine, such as that of Cuzco and the Peruvian coast, along with another tropical tuber, the yuca or manioc, went from South America and probably led to population booms where they were adapted, although that is not well documented yet for the sweet potato.