PALYNOLOGICAL EVIDENCE FOR CHANGING SUBSISTENCE PATTERNS AROUND MT WILHELM, PAPUA NEW GUINEA

Abstract

The staple food crop of the great majority of people in the central highlands of New Guinea today is the sweet potato (Impomoea batatas), a plant of tropical American origin. It is generally accepted that sweet potato arrived in New Guinea within the last four hundred years, following its introduction to island Southeast Asia by Iberian explorers in the early sixteenth century, although there have been occasional suggestions of an earlier entry through Polynesia (Gohon, 1977a). The in- troduction and acceptance of sweet potato must have caused a revolution in subsistence patterns in the New Guinea Highlands. Sweet potato matures more quickly, gives higher yields, has a longer pro- ductive life, is better pig fodder, and has a greater tolerance of poor or degraded soils than alternative staples (Golson, 1982). It also continues to be pro- ductive at higher altitudes, where its introduction would have permitted sustained and widespread agricultural settlement for the first time (Golson, 1977b). Palaeoecological investigations within the present day Highland's agricultural zone have provided evidence for some of the results predicted for the adoption of sweet potato, including increased agri- cultural settlement at higher altitudes and intensified land use at many sites (Golson, 1977b; Walker & Flenley, 1979; Oldfield et al., 1980; Powell, 1982). Above the altitudinal limits of agriculture, a pollen analytical study of the vegetation history of the last 22,000 years on Mt Wilhelm showed that significant disturbance of the forest near the treeline has occurred only during the last thousand years (Hope, 1976). A more detailed study of 28 sites within the Pindaunde Valley on Mt Wilhelm showed that, although local forest clearance started more than 700 years ago, the major clearance at most sites occurred within a few years of the same 300-year-old tephra fall which marks the start of agricultural intensification at lower altitudes in the Highlands (Corlett, in press). Forest clearance was almost certainly caused by fires lit by man during periods of exceptional drought. Here I present pollen diagrams from six additional valleys on Mt Wilhelm, as well as previously unpublished data on the regional pollen rain in the Pindaunde Valley, and discuss the relevance of the Mt Wilhelm clearance history to the question of when sweet potato was adopted as a staple crop and its impact on Highland's subsistence patterns. Plant names follow van Royen (1979). Dates are estimated calendar years B.P. (1 950 by convention), not radiocarbon years. THE STUDY AREA