Kuk Swamp: Early Agriculture in the Highlands of New Guinea

Kuk Swamp, in the highlands of Papua New Guinea, is one of the few places on Earth where agriculture developed independently. Excavations there have revealed evidence of plant cultivation going back as far as 10,000 years, with mounds for planting by about 7,000 years ago and drainage ditches by about 4,000 years ago. The site changed how archaeologists think about the origins of farming, showing that it was not only an invention of river valleys in Asia and the Americas.

Background: farming in a tropical highland

For a long time farming was thought to have begun in a handful of centres, such as the Fertile Crescent, China and Mesoamerica, and spread from there. New Guinea, a large tropical island north of Australia, was usually seen as a place that received crops and ideas from South-East Asia.

The New Guinea highlands, however, had been occupied by people for more than 40,000 years. Valleys between 1,200 and 2,000 metres above sea level offered fertile soils, plentiful rain and a climate free from malaria. People there relied on wild plants such as pandanus nuts, yams and taro long before any sign of farming.

Kuk lies in the upper Wahgi Valley near the town of Mount Hagen, at about 1,550 metres. Much of it is swamp, which made it hard to farm without drainage but excellent for preserving traces of ancient activity in layers of clay and volcanic ash.

Discovery and excavation

In the late 1960s a government agricultural research station was set up at Kuk to grow tea. When drainage channels were cut, they exposed ancient ditches and pits buried in the peat. The Australian archaeologist Jack Golson of the Australian National University began excavations in 1972 and continued work through the 1970s.

Golson argued that people had dug drainage channels at Kuk as early as about 9,000 years ago. This bold claim was difficult to prove, because the evidence for crops was then indirect. Many scholars remained cautious.

From the late 1990s Tim Denham and colleagues returned to the site with new methods. They studied starch grains and phytoliths, tiny silica particles from plants, preserved on stone tools and in sediments. Their results, published in the journal Science in 2003, provided much stronger evidence for early cultivation.

Three phases of cultivation

Researchers describe the early record at Kuk in three main phases.

Phase 1, about 10,000 years ago, includes pits, stake holes and a short channel cut into the wetland margin. Starch grains of taro and yams on stone tools show that these plants were being processed. Whether they were deliberately planted is debated, but many researchers see this as early plant management.

Phase 2, about 6,950–6,440 years ago, is clearer. People built mounds on the wet ground to grow plants that do not tolerate waterlogging. At the same time, phytoliths show that bananas of the Eumusa group became abundant, far more than would be expected naturally in the area. This points to deliberate cultivation of bananas.

Phase 3, from about 4,350–3,980 years ago, shows networks of ditches designed to drain the swamp for fields. Drainage systems were built, abandoned and rebuilt many times over the following millennia, right up to the recent past.

How archaeologists read the evidence

Kuk’s evidence is mostly invisible to the naked eye. Researchers examined the layered sediments of the swamp, where volcanic ash falls from distant eruptions form thin marker layers. These ash layers, together with radiocarbon dates, allow features such as pits and ditches to be placed in sequence.

Starch grains on the edges of stone tools show which plants were being scraped or cut. Phytoliths in the soil reveal which plants grew nearby. Pollen and charcoal record clearance of the forest by burning, which created an increasingly open, grassy landscape around the swamp over thousands of years.

Interpreting the results is not simple. A pit or a channel can have natural causes, and wild plants can leave the same microscopic traces as cultivated ones. This is why the strongest case for agriculture rests on several types of evidence together: the mounds, the unnatural abundance of bananas, the tools and the long-term clearing of the forest.

Crops of New Guinea

The plants grown at Kuk were local. Taro is a root crop with starchy corms, still a staple across the Pacific. Bananas were domesticated in the New Guinea region, and genetic studies suggest that New Guinea contributed key varieties of the edible banana grown around the world today. Sugarcane was very probably first domesticated in New Guinea as well.

Taro and many bananas are usually grown from cuttings and suckers rather than seeds. This makes their domestication harder to detect than that of cereals, because the plants do not change as quickly or as visibly. Researchers therefore combine archaeological remains with genetic studies of living crops to trace their origins.

Pigs and the sweet potato, now central to highland life, were later arrivals. Pigs reached New Guinea perhaps 3,000 years ago or later, and the sweet potato, a South American crop, arrived only within the last few centuries, after European voyages had carried it into the Pacific. Its arrival transformed highland farming and population.

An independent centre of agriculture

Kuk is the main evidence that New Guinea was one of the world’s independent centres of agriculture. Cultivation there began thousands of years before the Austronesian-speaking peoples linked to the Lapita culture arrived along the coasts of Melanesia, about 3,300 years ago.

The site also shows that early farming could look very different from grain fields. Instead of sowing cereals, highland people tended root crops and tree crops, often by cuttings, and managed the landscape through burning, digging and drainage. Comparing this with the Neolithic Revolution in the Fertile Crescent and the domestication of maize in Mexico shows how differently agriculture began in different parts of the world.

Debate continues over details, especially how to define agriculture in Phase 1 and how much of the early activity was planting rather than gathering. But few now doubt that New Guinea’s highlanders were farming by at least 7,000 years ago.

Recognition and protection

In 2008 the Kuk Early Agricultural Site, covering 116 hectares of swamp, was inscribed on the UNESCO World Heritage List as an example of technological change through time. It was Papua New Guinea’s first World Heritage Site. Local Kawelka people own and use the land, and their traditional cultivation continues around the protected area.

Timeline

• c. 8000 BC: Phase 1; pits, stake holes and a channel; taro and yam starch on stone tools.
• c. 5000–4400 BC: Phase 2; planting mounds and abundant banana phytoliths show cultivation.
• c. 2400–2000 BC: Phase 3; systematic drainage ditches for fields.
• c. 1300 BC: Austronesian-speaking Lapita peoples reach the Bismarck Archipelago, off New Guinea’s coast.
• 1972: Jack Golson begins excavations at Kuk.
• 2003: Tim Denham and colleagues publish new evidence in Science.
• 2008: Kuk inscribed as a UNESCO World Heritage Site.

Why it matters

Kuk Swamp shows that people in the tropical highlands of New Guinea invented farming on their own, with taro, bananas and yams, at roughly the same time as farmers in other parts of the world. It broadens the story of agriculture beyond cereals and great river valleys.