Early agricultural strategies in southern Polynesia

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES—Researchers report* fossil evidence of early taro cultivation in southern Polynesia, a region marginally suited for the tropical crop. The importance of the tropical crop taro during the early human colonization of New Zealand and other southern Polynesian islands is poorly understood. Little evidence of cultivation of the crop remains, in contrast to evidence of big-game hunting and later expansion of sweet potato crops. Matthew Prebble and colleagues collected sediment cores from three southern Polynesian islands: Ahuahu, Raivavae, and Rapa. The cores, containing fossil plants and animal remains, extend past the initial colonization period beginning in the 13th century CE. The results suggest a history of taro production in the islands, given that taro pollen appeared in the fossil records during 1300-1550 CE. The presence of pollen indicates flowering plants, which would be absent if the plants had been frequently harvested. During early cultivation, fire was likely used to clear forest cover, as suggested by sedimentary charcoal. Fire decreased over time, concurrent with an increase in short-lived plants, including weeds and leaf vegetables indicative of high-intensity production, forest decline, and species extinctions leading to widespread sweet potato cultivation by 1500 CE. According to the authors, the results show how Neolithic societies coped with the spread of tropical crops into marginal habitats.

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Map of the South Pacific Ocean showing the southern Polynesian islands (brown dashed line) examined in this study (blue boxes). Insets A-C show the study islands, including sediment core locations and high elevation points. Matthew Prebble

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Photomicrographs of the invertebrate fossil taxa. B, A1 (head, EA204, 210 cm to 220 cm, early garden), B, A2 (head, RAIDA4, 90 cm to 95 cm, late garden), B, A3 (elytron, EA204, 210 cm to 220 cm, early garden), B, A4 (thorax, EA204, 210 cm to 220 cm, early garden), and B, A5 (prothorax, EA204, 210 cm to 220 cm, early garden) are C. desjardinsi; B, B (forceps, TUKOU2, 58 cm to 60 cm, late garden) is E. annulipes; B, C1 and C2 (elytra, EA204, 170 cm to 180 cm, late garden) are Ataenius cf. picinus; B, D1 and D2 (heads, EA204, 170 cm to 180 cm, late garden) are Aleocharinae spp.; B, E1 (head, EA204, 190 cm to 200 cm, early garden) and B, E2 (pronotum, EA204, 190 cm to 200 cm, early garden) are Carpelimus sp.; B, F1 (elytron, EA204, 80 cm to 90 cm, PEC) is Dactylosternum cf. marginale; B, F2 (elytron, RAIDA4, 100 cm to 105 cm, late garden) is D. abdominale; B, G1 (elytron, EA204, 190 cm to 200 cm, early garden) is Saprosites sp.; B, G2 (elytron, RAIDA4, 50 cm to 55 cm, PEC) is S, pygmaeus; B, H (head, TUKOU2, 74 cm to 76 cm, late garden) is Tetramorium pacificum (Formicidae); B, I (head, EA204, 90 cm to 100 cm PEC) is Hypoponera cf. punctatissima (Formicidae); and B, J (head, RAIDA4, 95 cm to 100 cm, late garden) is Nylanderia sp. (Formicidae). (Scale bar, 0.5 mm.). Nicholas Porch and Matthew Prebble

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Article Source: PNAS news release

*”Early tropical crop production in marginal subtropical and temperate Polynesia,” by Matthew J. Prebble et al.