Washington, August 29 : A research paper has suggested that ancient settlements in the Amazon, now almost entirely obscured by tropical forest, were once large and complex enough to have hosted large, urban civilizations.
The paper has been co-authored by anthropologists from the University of Florida (UF) and Brazil, and a member of the Kuikuro, an indigenous Amazonian people who are the descendants of the settlements' original inhabitants.
The researchers argue that the size and scale of the settlements in the southern Amazon in North Central Brazil means that what many scientists have considered virgin tropical forests are in fact heavily influenced by historic human activity.
Mike Heckenberger, a UF professor of anthropology and the lead author of the paper, and his colleagues first announced the discovery of the settlements in a 2003 Science paper.
The largest date from around 1250 to 1650, when European colonists and the diseases they brought likely killed most of their inhabitants.
The communities are now almost entirely overgrown.
But, Heckenberger said that members of the Kuikuro, a Xinguano tribe that calls the region home, are adept at identifying telltale landscape features that reveal ancient activity.
These include, for example, "dark earth" that indicate past human waste dumps or farming, concentrations of pottery shards and earthworks.
Also assisted by satellite imagery and GPS technology, the researchers spent more than a decade uncovering and mapping the obscured communities.
The new paper reports that the settlements consisted of clusters of 150-acre towns and smaller villages organized in spread out "galactic" patterns.
None of the large towns was as large as the largest medieval or Greek towns.
But as with those towns, the Amazonian ones were surrounded by large walls - in their case, composed of earthworks still extant today.
Among other repeated features, each Amazonian settlement had an identical formal road, always oriented northeast to southwest in keeping with the mid-year summer solstice, connected to a central plaza.
Around the communities, the scientists also found dams and artificial ponds that indicate inhabitants farmed fish near their homes. They also found the remnants of open areas and large compost heaps suggesting widespread near-town cultivation.
The careful placement of the like-oriented settlements is indicative of the regional planning and political organization that are hallmarks of urban society, according to Heckenberger.
"These are not cities, but this is urbanism, built around towns," he said. "They have quite remarkable planning and self-organization, more so than many classical examples of what people would call urbanism," he added.