The terminal Pleistocene/Holocene boundary (approximately 12-8 thousand years ago) represented a major ecological threshold for humans, both as a significant climate transition and due to the emergence of agriculture around this time. In the highlands of New Guinea, climatic and environmental changes across this period have been highlighted as potential drivers of one of the earliest domestication processes in the world. We present a terminal Pleistocene/Holocene palaeoenvironmental record (12-0 thousand years ago ) of carbon and oxygen isotopes in small mammal tooth enamel from the site of Kiowa. The results show that tropical highland forest and open mosaics, and the human subsistence focused on these environments, remained stable throughout the period in which agriculture emerged at nearby Kuk Swamp. This suggests the persistence of tropical forest foraging among highland New Guinea groups and highlights that agriculture in the region was not adopted as a unilinear or dramatic, forced event but was locally and historically contingent.