The kumara, or sweet potato, Ipomoea batatas (L.) Lam., a member of the plant family Convolvulaceae, is cultivated for its edible swollen roots. The most important of the small array of Maori cultigens in pre-European times, it is the only one to become established in the modern New Zealand diet and is grown commercially in the Auckland Province. In the predominantly Maori communities of northern rural areas, kumara is still grown as a house-garden plant, and two groups of varieties are found – those considered to be of pre-European Maori introduction and those introduced by nineteenth century whalers. The latter, which were first planted by the Bay of Plenty Maoris, became widely distributed among northern tribes and the modern commercial types were derived from these varieties.
Maori traditions have placed the origin of the New Zealand kumara at the legendary Hawaiiki, and the time of introduction in the fourteenth century A.D. The advent of the kumara, representing the beginnings of agriculture, has been used as one of the points of separation between the two important developmental phases of Maori culture, the Archaic or Moahunter, and the Classic. Recent archaeological studies have questioned this late date for agricultural development. The discovery of pits, whose function may have been kumara storage, and dated at the time of purported introduction of the plant, infers either a very rapid development of the storage process not found in the rest of Polynesia, or an earlier date for kumara introduction. Whatever is postulated, there can be little doubt of the tropical origin of the Maori kumara. The adaptation of a plant, cultivated as a virtual perennial in the tropics, to the temperate New Zealand climate, involving an annual storage phase, constitutes one of the major achievements of early Maori agriculture. The role of the kumara in economic life is amply set out in the classic studies of Raymond Firth.
This is but a part of the story of the association between the plant and Pacific man. Early explorations of the islands of Polynesia, Melanesia, the East Indies, and the Philippines left records of the plant, some definite identifications, some doubtful. It was perhaps inevitable that much theorising on the origin of the plant and the identity of its distributors should ensue – especially with concurrent disputations on the botanical centre of origin, New or Old World. From the latter half of the nineteenth century a considerable literature on the subject has accumulated, with perhaps a peak of interest being aroused by Heyerdahl's use of kumara distribution in compiling evidence for his theory of the peopling of the Pacific from America.
Analyses of recent data from botanical, agricultural, and linguistic sources indicate the following pertinencies. The kumara is of American origin. A wild species of Ipomoea found in Mexico, on cytogenetic investigation, has proved to be more closely related to the kumara than any other species so far studied. Further, the range of variation displayed by a South American collection of varieties exceeds that found within a collection representative of Polynesian and Melanesian islands and South-East Asia. Again, the distribution in the Pacific is not the product of a single introduction and subsequent diffusion. Independent studies, one on the variation of vernacular names applied to the plant in the western Pacific, the other on plant variation already referred to, indicate that a likely explanation for distribution is a three-stream introduction from America; the first, in prehistoric times to Polynesia, followed by two early historic introductions – by the Portuguese to the East Indies, diffusing to Melanesia, and by the Spanish from their American colonies to the Philippines, from whence the plant reached mainland Asia. The possibility that the Portuguese introduction was made by a circuitous route from the Caribbean through Africa and the Indian Ocean cannot be dismissed.
The carriers of the earliest Pacific kumara, the Polynesian, remain unidentified, but the question must resolve itself into two alternatives – voyages by Polynesians to the western shores of South America, or prehistoric visits of American peoples to Polynesia. The increased activity in archaeological research of recent years may yet provide a firmer answer than the deduction on agricultural premises, which favours transfer by the Polynesians.
by Douglas Ernest Yen, M.AGR.SC., Crop Research Division, Department of Scientific and Industrial Research, Otahuhu.
- The Kumara in New Zealand: Dominion Museum Bulletin No. 9 (1925), “The Maori System of Agriculture”, Best, E.
- The Coming of the Maori, Buck, P. (1958)
- The Moahunter Period of Maori Culture, Duff, Roger (1956)
- Economics of the New Zealand Maori, Firth, R. (1959)
- Anthropology in the South Seas, Freeman, J. D., and Geddes, W. R., eds. (1959), “Culture Change in Prehistoric New Zealand”, Golson, J.
- Journal of the Polynesian Society, Vol. 70 (1960), “The Adaptation of the Kumara by the New Zealand Maori”, Yen, D. E.
- Origin and Distribution of the New Zealand Kumara: Plants and the Migration of Pacific Peoples, Barrau, J., ed. (1963)
- The Origin of Cultivated Plants, de Candolle, A. (1959)
- American Indians in the Pacific, Heyerdahl, T. (1952)
- The Island Civilisations of Polynesia, Suggs, R. C. (1960).