‘Humans in one of the earliest areas of settled agriculture were not forced to farm’

The development of agriculture is universally believed to underpin some of the most significant advances made by humans worldwide. In New Guinea where one of the earliest human experiments with tropical forest agriculture occurred, researchers from the University of Oxford, the Max Planck Institute for the Science of Human History, and the University and Otago, have cast doubt on two views about the origins of agriculture. One is that climate variability after the last Glacial period drove such innovation out of necessity, and the other is the view that early hunter gatherers could not survive successfully in tropical forest environments without domestic crops and animals. They found little evidence for climate variability from 12,000 to 300 years ago, instead it appears that the montane tropical forests of New Guinea provided a stable source of subsistence for human hunter-gatherers although there were also farmers working the land close by. The findings are published in the early online edition of the journal, Nature Ecology and Evolution.

Scholars have regarded tropical forests as unattractive habitats for humans due to their poor soils, high humidity, and they were not thought capable of producing regular sources of food. Archaeological work in New Guinea, among other tropical regions, has overturned this idea as researchers discovered that humans have occupied areas of this region (today covered in rainforest) for around 45,000 years. The team analysed the teeth of small mammals like fruit bats, cuscus, ring-tailed possum and macropods from the archaeological site of Kiowa. The remains are from 12,000 to 8,000 years ago, when agriculture in the region first started, up to around 300 years ago. These animals are locally well-studied and are documented as being hunted by local foragers into recorded history. Due to their short life cycles and specialised adaptations, these animals are highly sensitive to environmental change, which makes them good proxies for the ‘local’ picture of vegetation, says the paper.

The results provide a new, rare environmental record for the Central Highlands of New Guinea. The dietary signatures obtained from the mammals’ teeth show that for thousands of years the local climate was stable, and was occupied by humans throughout the period. There was no obvious signs of sudden climate change that propelled them into having to become more organised in how they obtained their food, suggests the paper.

‘This research enriches our understanding of the origins of agriculture in the region, indicating that stable tropical environments supported both agricultural experimentation and ongoing tropical forest foraging within a small area,’ explains co-author Dylan Gaffney of the University of Otago.

‘While there was intensive farming, including the domestication of crops such as the banana, yam, and taro, we can assume from this record of small mammals that because the animals survived throughout the period, human foragers could also hunt successfully in tropical forest environments. We believe they were not forced to become farmers in order to survive,’ says lead author, Patrick Roberts, of the University of Oxford and the Max Planck Institute for the Science of Human History.

‘We have assumed in the past that agriculture is a desirable invention, replacing previous ways of obtaining food in prehistoric New Guinea. These findings suggest that agriculture is one way in which humans changed the landscape, but in this area it was certainly not an inevitable development,’ adds Roberts.

Professor Summerhayes notes, ‘By continuing to use methods such as those applied here, in different tropical forest environments worldwide, will begin to produce large datasets with which the ecological challenges faced by our species, and the behaviours used to overcome these challenges, can be explored for some of the most bio-diverse, but now threatened, of the world’s terrestrial environments.’

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