The history of the human landscapes of New Guinea
The pollen of Casuarina becomes much more common across the highlands after ca 1800 years ago suggesting that this was a time of widespread silvicultural planting. This rapid spread supports an hypothesis that there was effective diffusion of ideas despite linguistic and social barriers. Similarly the spread of crop plants such as sweet potato also seems to have been almost universal in the highlands resulting in the new clearance of slopes and higher altitudes that becomes apparent in the last few centuries, and in the abandonment of some swampland field systems.
This thumbnail sketch of 50,000 years of history conceals the major feature of New Guinea that operates through time as well as across the island—its habitat diversity and unusual position as one of the world’s wettest regions. The topographic range and position next to the Western Pacific Warm Pool has preserved this diversity through the climatic fluctuations of the late Pleistocene, but boundaries have shifted dramatically and few places have been unaffected. The general picture of change can not yet be predicted at the local level and this has hindered the reconstruction of human environments. We can be quite sure that the modern barrier that separates the highlands from the coast—the everwet lower mountain forest zone—has remained intact throughout the period of human occupancy. Yet this is principally a barrier to agriculture and might have had some attractions for hunting and foraging, although humans do not thrive there today due to malaria, skin diseases and other problems (Riley 1983). At higher altitudes the highland valleys also supported dense wet forests with few resources during glacial times yet some settlement did take place.
New Guinea possibly had its ‘big game hunters’ in the Pleistocene, but the evidence is so diffuse that we can only note another unexplained extinction event and wonder if there might be anything in the origin myths of strange animals and birds. However the loss of species of rodents in the islands (Spriggs 1997) around 30,000 years ago is clearly coincident with human settlement. Flannery (1992) has suggested that a second phase of effective hunting of arboreal mammals could only start when the dog arrived about 3500 years ago. With the establishment of large areas of secondary vegetation a reduction in the significance of hunting has continued to the present day. In the upper Chimbu Valley in Simbu the animal called Inkomugl in the vernacular was widely remembered in 1970, even though no-one had ever seen one (Sterly 1997). This was the monotreme Zaglossus bruijnii, now probably wiped out near large population centres but preserved in stories.
The diversity of culture and language must reflect the need for local adaptation to specific environments that change over distances of a few kilometres. Yet on a long time scale of many centuries similar patterns of settlement and technology appear at the same time across the island. Diffusion of cultivars, land management practices and other techniques such as pottery or silviculture was probably relatively rapid despite the isolation of groups. The most rapid time of climate change and coastal stress, from ca 15– 8000 years ago, rewarded adaptive cultures. The burning of some of the high altitude grasslands by 13,000 BP, 4000 years before the substantial clearance in the montane basins, suggests that trading links were in place across the mountains before the agricultural populations had increased. Similarly the scattered evidence for clearance and burning by 30,000 BP suggests that some ecological manipulation and selection was already taking place. Hence the emergence of an agricultural landscape in the highlands of