Amazon Archaeology

Most of the soil around the Amazon river is chalky and acidic — poor for farming.

That’s why archaeologists assumed no advanced civilizations arose in the Amazon basin before European colonization. But Brazilian farmers know of patches of thick, dark soil they call Terra Preta — or Black Earth. Here’s Jim Petersen is an archaeologist at the University of Vermont . . .

Jim Petersen: Analyses done on Terra Preta — or black earth soils — have shown that the native people may have been intentionally creating these. By taking vegetation from the numerous waterways or rivers in the Amazon and mulching, if you will, the soils to increase their organic content, thereby increasing their fertility.

Recent studies show that Terra Preta — which is often full of pottery shards — began appearing at least 2,500 years ago. Dr. Peterson thinks this soil might hold clues to an ancient advanced civilization.

Jim Petersen: So I think the Amazon is . . . an archaeological frontier in a very real sense.

Amazonia: Man & Culture in a Counterfeit Paradise

In 1971, anthropologist Betty Meggers published a book that came to dominate anthropological thinking about the Amazon rainforest. _Amazonia: Man & Culture in a Counterfeit Paradise_ suggested that there was nothing worth finding in the Amazon basin. The caricature of the argument says the rainforest’s notoriously poor soils could never accommodate the kind of agriculture that advanced civilizations require, so looking for the signs of lost cities and large, organized societies is a waste of time.

Anthropology holds that the standard mode of human survival in infertile tropical zones is one of slash & burn agriculture: Across Africa, New Gunea and the Amazon, small groups burn through the jungle to clear space for farming. They cultivate the ground for short periods of time, then move on after depleting the soil’s scarce nutrients. Scientists assumed this is how it was done in the Amazon for the past hundreds and thousands of years — that the land was inhabited only by small roving groups practicing slash-and-burn agriculture.

But recent analysis of the jungle’s rich Terra Preta, is changing that outlook. Soil scientists have found that the dark earth is bursting with organic matter that seems to have been introduced by intensive mulching and cultivation. The soil is rife with wood ash and charcoal, the remains of fish processing, and a large component that comes from a variety of marsh and aquatic plants — even in areas far above and away from rivers.

“There’s a very close correlation with archaeological sites of prior occupation and these soils,” said William Woods, a geographer at Southern Illinois University, Edwardsville. Woods has studied human-modified soils for more than 30 years. “It’s very clear that prior inhabitants changed them and pretty darn clear that they did it intentionally.”

Terra Preta seems to have been produced consistently until the arrival of Europeans in the 1500’s. Within a few hundred years, it covered an estimated 10 percent of the Amazon region.

University of Vermont archaeologist Jim Petersen, has excavated at some of the Terra Preta sites near the Amazon River. He says the people who made these soils were not just small groups. At one site, his team excavated two cubic meters of ground, and found the remains of more than 1,000 different ceramic vessels representing dozens of different forms. There were cups and multi-colored feasting bowls with effigies on them, large jars for holding manioc beer and griddles for frying manioc bread. Pottery remnants are so plentiful throughout the dark earth sites that Petersen estimates there may be over 1 million ceramic vessels in some of the larger sites — sites which are miles across.

Petersen predicts the counterfeit paradise paradigm may begin to wobble as a result of recent research into Terra preta sites. “We think that the Amer-Indians were larger, living for longer periods and more socially complex. Now with the Terra Preta research that’s ongoing, we may also find that they were more environmentally in tune, and that they were environmental managers and instead of being constrained by the environment, they were managing it to their benefit.”

Managing in a way that modern humans would love to learn

Petersen and a colleague first started interest in the dirt — noticing that it seemed to be correlated with sites of human habitation — in 1994. But it was localized. The realization that these sites are of a huge wide scale, and are bursting with ceramics, and the soil studies, the microbiology etc. that show mulching and advanced soil engineering were in the spring, summer and fall of 2002. The work is very current and ongoing. A lot of the “wow, this is bigger than we thought” stuff was the result of a big conference in Brazil this past summer [2002], the proceedings of which are being edited and set to be published next year.

I asked Jim Peterson to describe his upcoming work [in the summer of 2003] He replied: “Our Amazon archaeology work will resume next summer when a team from the University of Sao Paulo and my institution will return to the Manaus area, probably not until July, however. We will be using standard techniques when in the field next summer, BUT we are planning first on looking at a potentially really old Terra Preta site, much older than we have ever seen or even guessed at, perhaps even 9000 years old or older (on the basis of limited work done to date…).”

Peterson also says that a month of field work requires months of work in the lab to analyze. So he’s currently analyzing over three years worth of data he’s already collected.

See also “AGRICULTURE: The Real Dirt on Rainforest Fertility,” in Science August 9, 2002.

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