America could not be left alone any longer, and so about 1000 years ago Norse (Viking) people settled in Vinland (L'Anse aux Meadows - an archaeological site in Newfoundland, Canada). About the same time Polynesian sailors visited the coast of Ecuador-Peru in South America. While the Vinland settlement produced no lasting legacy for Americans or Europeans, Polynesian contact was felt across the Pacific.
Soon sweet potato was adopted in Cook Islands and Hawaii. In Rapa Nui (Easter Island) – some scholars argue – it supported sizable population and permitted monumental construction projects, including the famed stone figures.
When exploring New Zealand in 1642 some of Abel Tasman’s crew were attacked and killed. Two Tasman’s vessels chased by 11 Maori canoes departed hastily from what is now Golden Bay on the north end of South Island. Recent archaeological research has finally explained the reasons behind the attack – it was to protect the near fields of sweet potato – not only an important staple for the local community but a crop of high symbolic and spiritual significance.
The socioeconomic and spiritual importance of sweet potato, as well as an effort necessary to cultivate and care for the crop, made its protection paramount. In addition, as a result of the small climatic shift after the 15th century the overall temperature was lowered making it even harder to grow this plant on the South Island.
By that time the Spanish, conducting an intense trans-Pacific trade, introduced sweet potato into many other islands. It was embraced enthusiastically in the New Guinea highlands and eventually found its way to Southeast Asia. It became one of the most important crops in some parts of Melanesia, as well as significant food in equatorial Africa and Asia.
Why and how did Polynesians adopted sweet potato? And why not other South American food plants? The convincing explanation looks at the similarity between ufi (common yam) - from the beginning universally used through Polynesia - and sweet potato kumara. Although they are completely unrelated plants, it is possible that sweet potato was ‘taken’ by Polynesians as another type of yam. Not by mistake, but as an integral part of their broad system of cultural practices and willing acceptance. The two plants have similar vine-tuber character, broadly parallel propagation method, transport, storage and food-preparation. And in many cultures, including Maori, sweet potato was given the same, if not greater, spiritual and mythological importance than yam.
Ian Barber, 2012. Gardens of Rongo: Applying Cross-Field Anthropology to Explain Contact Violence in New Zealand. Current Anthropology: 53 (6).
Helen Leach, 2005. Ufi kumara, the sweet potato as yam. (in) The sweet potato in Oceania: a reappraisal. Oceania Monograph 56.