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By Root 1976 0

times without economically significant inputs from societies outside the highlands, and without inputs of any sort except trade items prized just for status (such as cowry shells and bird-of-paradise plumes). New Guinea is the large island just north of Australia (map, p. 84), lying almost on the equator and hence with hot tropical rainforest in the lowlands, but whose rugged interior consists of alternating ridges and valleys culminating in glacier-covered mountains up to 16,500 feet high. The terrain ruggedness confined European explorers to the coast and lowland rivers for 400 years, during which it became assumed that the interior was forest-covered and uninhabited.

It was therefore a shock, when airplanes chartered by biologists and miners first flew over the interior in the 1930s, for the pilots to see below them a landscape transformed by millions of people previously unknown to the outside world. The scene looked like the most densely populated areas of Holland (Plate 19): broad open valleys with few clumps of trees, divided as far as the eye could see into neatly laid-out gardens separated by ditches for irrigation and drainage, terraced steep hillsides reminiscent of Java or Japan, and villages surrounded by defensive stockades. When more Europeans followed up the pilots’ discoveries overland, they found that the inhabitants were farmers who grew taro, bananas, yams, sugarcane, sweet potatoes, pigs, and chickens. We now know that the first four of those major crops (plus other minor ones) were domesticated in New Guinea itself, that the New Guinea highlands were one of only nine independent centers of plant domestication in the world, and that agriculture has been going on there for about 7,000 years—one of the world’s longest-running experiments in sustainable food production.

To European explorers and colonizers, New Guinea highlanders seemed “primitive.” They lived in thatched huts, were chronically at war with each other, had no kings or even chiefs, lacked writing, and wore little or no clothing even under cold conditions with heavy rain. They lacked metal and made their tools instead of stone, wood, and bone. For instance, they felled trees with stone axes, dug gardens and ditches with wooden sticks, and fought each other with wooden spears and arrows and bamboo knives.

That “primitive” appearance proved deceptive, because their farming methods are sophisticated, so much so that European agronomists still don’t understand today in some cases the reasons why New Guineans’ methods work and why well-intentioned European farming innovations failed there. For instance, one European agricultural advisor was horrified to notice that a New Guinean sweet potato garden on a steep slope in a wet area had vertical drainage ditches running straight down the slope. He convinced the villagers to correct their awful mistake, and instead to put in drains running horizontally along contours, according to good European practices. Awed by him, the villagers reoriented their drains, with the result that water built up behind the drains, and in the next heavy rains a landslide carried the entire garden down the slope into the river below. To avoid exactly that outcome, New Guinea farmers long before the arrival of Europeans learned the virtues of vertical drains under highland rain and soil conditions.

That’s only one of the techniques that New Guineans worked out by trial and error, over the course of thousands of years, for growing crops in areas receiving up to 400 inches of rain per year, with frequent earthquakes, landslides, and (at higher elevations) frost. To maintain soil fertility, especially in areas of high population density where short fallow periods or even continuous growing of crops were essential to produce enough food, they resorted to a whole suite of techniques besides the silviculture that I’ll explain in a moment. They added weeds, grass, old vines, and other organic matter to the soil as compost at up to 16 tons per acre. They applied garbage, ash from fires, vegetation cut from fields resting in fallow,