Ancient Town Among Dozens of Hidden Structures Found In Amazon Rainforest

Researchers have discovered two dozen ancient constructions hidden beneath the canopy in the Amazon rainforest basin.

The constructions are earthworks built in the pre-Columbian era—meaning prior to the period of European colonization. They represent the remnants of a variety of sites and structures built by ancient Indigenous peoples.

The previously unknown earthworks include the remains of an ancient town, fortified villages; defensive and ceremonial structures known as geoglyphs; and riverbank sites on floodplains that may have been used to gather aquatic food; among other constructions, according to a study published in the journal Science.

Indigenous societies are known to have lived in the Amazon region for at least 12,000 years, creating earthwork structures and domesticated landscapes that have had long-lasting effects on the forest.

However, the scale of these societies' influence on the forest remains poorly understood. Primarily, this is due to the fact that finding evidence of them is very challenging given the density of the forest canopy and the remoteness of many archaeological sites.

In the latest study, a large international team of researchers examined a dataset collected using LiDAR (light detection and ranging) technology, which enabled them to identify 24 previously unknown earthworks in the region.

The LiDAR survey, which covers more than 2,000 square miles of the Amazon Basin, was originally obtained for estimating biomass throughout the forest.

"Most of the data was collected randomly for biomass estimates, not for archaeological prospecting purposes, so initially, we were not sure if we would find anything. It was a risk that fortunately paid off," Vinicius Peripato, a doctoral student in Remote Sensing at the Brazilian National Institute for Space Research and co-lead author of the study, told Newsweek.

LiDAR essentially allows scientists to see through the forest canopy and create detailed 3D models of the surface elements, including any unknown structures that lie below.

"Our study suggests that the Amazon rainforest may not be as pristine as many believe, as when we seek a better understanding of the extent of pre-Columbian human occupation throughout it, we are surprised by a significant number of sites still unknown to the science community," Peripato said in a press release.

"From the 3D models of the surface, it is possible to digitally remove all vegetation and initiate a precise and detailed investigation of the terrain beneath the forest."

Among the 24 previously unknown earthworks that the team discovered was a type of ancient, fortified settlement known as a "plaza town"—located in southern Amazonia.

These settlements were surrounded by large ditches measuring several feet deep, 30-50 feet across and more than 1 mile in length. They had a circular central plaza, which was surrounded by large earthen mounds, and straight roads up to around 130 feet wide emanating from the plaza in a radial pattern.

In the study, the scientists also modeled the occurrence of other ancient earthworks across the Amazon, predicting that anywhere between roughly 10,000 and 24,000 are waiting to be discovered in the region.

The latest findings shed new light on the influence of pre-Columbian societies in the Amazon region.

"Some time ago, ecologists viewed the Amazon as the vast untouched forest, but now, combining other types of pre-Columbian remains, we can see how many areas that currently sustain dense forest have already been subjected to extensive engineering works and the cultivation and domestication of plants by pre-Columbian societies," Carolina Levis from the Federal University of Santa Catarina in Brazil said in the press release.

"These people mastered sophisticated techniques for land and plant management, which in some cases, are still present in the knowledge and practices of present-day communities that can inspire new ways to coexist with the forest without the need for its destruction."

The LiDAR survey data collected for the study only covered 0.08 percent of the total area of Amazonia, but the researchers wanted to better understand where and how many undocumented pre-Columbian sites there might be in the region.

In order to do this, the scientists combined the data from their relatively small survey with knowledge from previously identified sites to create a predictive model that could estimate the occurrence of pre-Columbian structures.

This model indicated that between 10,272 and 23,648 large-scale pre-Columbian structures remain to be discovered, particularly in southwestern Amazonia.

Furthermore, the researchers found an association between the predicted locations of earthworks and the abundance of dozens of domesticated tree species. This suggests that active pre-Columbian Indigenous forest management practices have long shaped the ecology of modern forests across Amazonia.

"Amazonian forests clearly merit protection not only for their ecological and environmental value but also for their high archaeological, social, and biocultural value, which can teach modern society how to sustainably manage its natural resources," the authors wrote in the study.

Most Amazonian earthworks that have been identified to date were uncovered due to deforestation.

"The deforestation in these areas is already a significant interference in these locations," Peripato told Newsweek. "Furthermore, not all of these records are reported to government agencies, and as a result, many have already been compromised, due to land use conversion for agriculture or cattle ranching. In these cases, there is a severe loss of archaeological assets and data collection opportunities.

"Thus, new discoveries in preserved environments bring great research opportunities regarding the ancient Amazonian peoples, with promising results in archaeology, anthropology, and ecology."

Update 10/11/23, 10:28 a.m. ET: This article was updated with additional information from Vinicius Peripato.