Long before the Spaniards first arrived in the Americas, the Incas told stories of a mighty civilization in the watery plains to the east of the Andes. In the fifteenth century the Inca Yupanqui sent a great army down one of the rivers of the Upper Amazon in search of this kingdom. Ravaged by the exigencies of the jungle, the depleted army finally met its match in the warlike Musu, or Moxos peoples, among whom the surviving Incas settled. Hearing tales of this mythical realm, known, variously, as El Dorado and Paitití, Spanish conquistador Gonzalo Pizarro led a huge expedition down into the Amazon in 1541. Though the gold dust of their fevered imaginings was nowhere to be found and the expedition ended – like so many others after it – in despair and death, Dominican friar Gaspar de Carvajal chronicled sightings of roads, riverbanks thronged with people, exquisite ceramics and, famously, “cities that glistened in white”. While his reports were initially shelved and later disparaged, recent archeological discoveries look, centuries later, to be finally proving him right.

The archeological evidence

Until about forty years ago archeologists doubted that any large, settled population could ever have survived in the Amazon Basin. The accepted wisdom was that the region’s thin, acidic soils made intensive agriculture impossible, and that the area could support only small, scattered communities practising slash-and-burn agriculture along with hunting and gathering. But subsequent research has suggested that the forests and savannahs of the Llanos de Moxos were in fact once densely populated by well-organized societies who, sometime between 3000 BC and 1000 BC, modified the environment on a massive scale to allow intensive agriculture and large urban settlements. The region is dotted with hundreds of raised earth mounds, known as lomas, most of which are covered by forest. Seen from the ground, these mounds are hardly impressive, and were long thought to be merely the remnants of natural levees left by rivers as they meandered across the plain. But when archeologists looked at these mounds from the air, they realized they were far too extensive and regular to be natural.

Instead, they concluded that they were the remnants of a massive system of earthworks – including raised fields, canals, causeways, reservoirs, dykes and mounds stretching over hundreds of square kilometres – that could only have been built by a large and well-organized society. Excavations on some of the mounds revealed that they had been built up over many centuries. By cultivating these raised mounds, researchers believe the ancient inhabitants of the Moxos were able to overcome the problems of poor soil and seasonal flooding and drought, producing enough food to support a population density much greater than was previously believed possible in the Amazon. Moreover, further north in the Brazilian, once-Bolivian, territory of Acre, deforestation – together with the wonders of Google Earth – has revealed hundreds of geoglyphs of similar magnitude, while excavations of terra preta, or ultra-fertile soil cultivated by humans, seem to coincide with the locations of the riverside cities described by Carvajal.

These discoveries have enormous implications for both conservation and development in the Amazon. They suggest that, far from being a fragile natural environment, large areas of the Amazon are in fact anthropogenic, or man-made, ecosystems, modified by centuries of human activity and even now capable of supporting far larger populations than is currently the case.

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