Peatlands are common in montane areas above 1,000 m in New Guinea and become extensive above 3,000 m in the subalpine zone. In the montane mires, swamp forests and grass or sedge fens predominate on swampy alley bottoms. These mires may be 4–8 m in depth and up to 30,000 years in age. In Papua New Guinea (PNG) there is about 2,250 km2 of montane peatland, and Papua Province (the Indonesian western half of the island) probably contains much more. Above 3,000 m, peat soils form under blanket bog on slopes as well as on valley floors.
Two of the unanswered questions of Papua New Guinea prehistory are: (1) whether agriculture was present
in the mid-Holocene not only in the highlands but also in the lowlands and Bismarck Archipelago and (2)whether the presence of agriculture might have been influenced by interaction between these regions. This paper addresses these questions through an analysis of prehistoric stone mortars, pestles and figures, which hold information on both style and function.