Amazon reveals ancient villages
BRAZIL: The settlement looked like little more than 11 mounds of earth surrounded by a sunken ditch. But if Jonas Gregorio de Souza closed his eyes, he could imagine the Boa Vista site as it would have appeared 800 years ago.
Perhaps, the archaeologist said, those mounds were houses circling a central square. Outside the defensive ditch, gardens and fruit trees might have flourished. The road leading to the enclosure may have had a ritual purpose, its surface hardened by countless ceremonial processions. Or maybe it linked the village to others, forming a chain of communities that criss-crossed the whole southern Amazon basin.
There was a time when no archaeologist expected to discover such an elaborate settlement in this relatively resource-poor part of the rainforest. But in a paper published yesterday in the journal Nature Communications, de Souza and his colleagues describe the mound village and 80 other newly discovered archaeological sites from the years 1250 to 1500.
They predict the region hides hundreds more undiscovered sites, and that as many as a million people might have carefully managed the rainforest long before Europeans arrived.
‘‘It’s an important paper,’’ said Dolores Piperno, an archaeobotanist at the National Museum of Natural History who has worked extensively in the Amazon but was not involved in the new study.
Though she wasn’t quite convinced by de Souza’s conclusions about the size of the region’s pre-Columbian population, the discoveries add to a growing body of evidence that large communities flourished in one of the world’s most diverse landscapes.
Fifty years ago, she said, ‘‘prominent scholars thought that little of cultural significance had ever happened in a tropical forest. It was supposed to be too highly vegetated, too moist. And the corollary to those views was that people never cut down the forests, they were supposed to have been sort of ‘noble savages’.’’
‘‘But those views have been overturned,’’ Piperno said. ‘‘A lot of importance happened in tropical forests, including agricultural origins.’’
Collaborating with scientists from Britain and Brazil, de Souza, a research fellow at the University of Exeter in England, identified the new archaeological sites by looking at satellite images of the Upper Tapajos Basin, on Brazil’s border with Bolivia.
This area is considered a ‘‘transitional zone’’, where rainfall is more sparse and seasonal and the rainforest shifts into a savannalike ecosystem. Since the basin is far from the floodplains that enrich other landscapes, researchers have long overlooked it, de Souza said, assuming it couldn’t sustain large groups of people.
But the aerial surveys revealed dozens of geoglyphs – geometricshaped trenches carved into the earth. Though the sites range in shape and size – the smallest is just 30 metres across, the largest almost 400 metres – many were like Boa Vista, harbouring villages inside or nearby.
De Souza and his collaborators spent a month conducting on-theground surveys of 24 of those sites. All of them contained evidence they had been inhabited: abandoned stone tools and broken ceramics, buried rubbish heaps, an enriched soil called terra preta that is characteristic of indigenous land management through burning and adding fertiliser. By measuring how much of samples’ radioactive carbon had decayed over the years, the researchers dated wood charcoal found at the sites to the early and mid-1400s.
Since the 1970s, scientists have identified large, elaborate geoglyphs across other parts of the Amazon. Some have estimated there is about 15.5 million hectares of terra preta in the basin. Others’ research shows entire regions of the rainforest are dominated by tree species once cultivated for food by indigenous people. And highly planned networks of villages have been identified on either side of the region de Souza studied.
The latest discovery, de Souza said, suggests there was a continuous string of settlements across the southern rim of the Amazon basin.
‘‘It seems that it was a mosaic of cultures,’’ he continued. The villages shared some practices – enriching the soil, cultivating brazil nut and cocoa trees, encircling their homes with protective ditches – but spoke a diverse array of languages.
Plugging their findings into models that predict population densities, de Souza and his colleagues estimate that between 500,000 and a million people lived in this part of the Amazon.
De Souza said he and his colleagues plan to conduct surveys seeking more settlements.
‘‘It’s probably the case that some areas of the Amazon were sustaining large populations and others were not,’’ he said. ‘‘Because there is so little research, we are slowly discovering what was happening in each.’’
These discoveries don’t affect just our understanding of the past; they have implications for the future. Huge swaths of the Amazon are being lost to logging, clearcutting for agriculture, wildfires, dams, mining and other forms of habitat degradation. The rainforest’s ability to act as ‘‘the lungs of the world’’ by inhaling carbon dioxide is declining.
Though conservationists often speak of this region as having been a ‘‘pristine’’ landscape, studies by de Souza and others suggest that indigenous people influenced and enriched the rainforest for hundreds of years.
If we want to preserve the Amazon, researchers say, we need to take those impacts into account.
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