The Amazon Hid Tens of Thousands of Ancient Earthworks
Wetland towns built mounds and raised roads and farmed rich black soil that villagers still prize today.
Shawn Ryan Show · #335 Ed Barnhart - The Amazon Rainforest is Hiding a Lost Civilization?One part of the Amazon could hold 24,000 to 30,000 ancient earthworks, according to a recent estimate, with perhaps millions of residents at its height.
That count suggests the familiar picture of an untouched rainforest was instead a farmed landscape of towns, roads, and rich black soil.
Ed Barnhart, a Maya archaeologist who works in Guatemala and Mexico, said he predicted in a lecture series in 2009 that work in the Amazon would “freak us out” within a decade.
These so-called geoglyphs are actually enclosures around big communities, he said. Different places handled that wetland environment in different ways.
In Bolivia, he said, people built big mounds with raised causeways, or raised roads over the wetlands, running out to smaller mounds and houses, and farmed the wetlands into what he called an agricultural paradise that was still in use at Spanish contact.
About a century after Spaniards first reached the region, priests who went down to those Bolivian communities to convert residents wrote journals about them. One priest complained that residents had built a magnificent system of causeways and used it only “to go from party to party,” with constant celebrations and no use for commerce or education, Barnhart said.
On a weeklong boat trip up the Black River from Manaus, Barnhart said he asked modern Indigenous villagers why they placed their villages where they did. The answer was always the same: pockets of dark, highly productive earth called terra preta.
Archaeologists now describe that landscape as anthropogenic, meaning people made it. Centuries or even millennia of living and farming built up large areas of black soil, which villagers still choose for planting even when they do not know its history. So far that evidence comes from areas around the wettest heart of the Amazon, he said. That may be because archaeologists have not yet worked farther into unknown ground, or because even those adaptations would not work in the deepest water.
Questions people ask
What exactly is terra preta?
Terra preta is a dark, fertile Amazonian soil enriched with charcoal, bone, ash, and organic waste from long human occupation. It holds nutrients and moisture far better than the region's naturally thin, acidic soils, so crops grow much better in it. Large patches mark where people lived and farmed intensively for centuries.
What does an Amazon earthwork look like?
An earthwork is any shape made by moving earth, including ditches, walls, mounds, and raised roads. In the Amazon, many are large circular or rectangular enclosures around old settlements, plus house mounds and causeways over wetlands. From the ground they look like small hills, so many were only recognized through clearing, excavation, or remote sensing.
Why build causeways and mounds in wetlands?
Seasonal flooding makes normal paths and fields unusable for months. Raised causeways stayed above the water for travel, while raised planting areas kept roots from drowning and helped control water and nutrients. Together, they let dense communities live and farm in wetlands that look impassable today.