Researchers in the Brazilian Amazon have found 25 long-abandoned villages laid out in patterns resembling a clock face, with mounds circling a central plaza.
As Laura Geggel reports for Live Science, the villages, located in what’s now the state of Acre in western Brazil, date to between 1300 and 1700. A team of scientists from South America and the United Kingdom used helicopter-mounted LiDAR—the same “light detection and ranging” technology used in self-driving cars—to peer below the rainforest foliage and get a big-picture view of structures in the area. In addition to the circular communities, the researchers found 11 other villages laid out in rectangular patterns and 15 that were too run-down to get a sense of their layout. The work is published in the Journal of Computer Applications in Archaeology.
“LiDAR has allowed us to detect these villages, and their features such as roads, which wasn’t possible before because most are not visible within the best satellite data available,” says lead author José Iriarte, an archaeologist at the University of Exeter, in a statement. “The technology helps to show diverse and complex construction history of this part of the Amazon.”
Per Science Alert’s David Nield, the archaeologists found between 3 and 32 mounds ranging in height from under 10 feet to more than 65 feet at each site. They are unsure what the mounds’ purpose was but posit that the structures may have served as houses or burial places.
The LiDAR images also revealed the pattern of sunken roads with high banks that extend from most of the villages. In most cases, two major roads extend to the north, while two travel south. The roads often connect one village to another in networks stretching for many miles.
Arranged in symbolically significant ways with no clear hierarchy, the villages’ circular layouts may reflect their Indigenous inhabitants’ conceptions of the cosmos. The authors say the new work helps paint a picture of the long human history of the area. Hundreds of years prior to the mound-building culture’s rise, locals erected large, geometrically patterned earthworks, but they abandoned these structures around 950 A.D.
For years, many archaeologists had believed that this region of the rainforest was only sparsely occupied in the centuries before European colonization. As Sarah Kaplan reported for the Washington Post in 2018, Iriarte and his colleagues have previously used satellite images to investigate the history of the region, documenting its changing civilizations and cultures. Among the achievements of premodern rainforest residents is the creation of enriched soil, or terra preta, which enabled communities to produce food in a landscape that would have otherwise been inhospitable.
In the statement, Iriarte says the laser technology, combined with other techniques, is expanding the work that researchers can do with limited resources.
“LiDAR provides a new opportunity to locate and document earthen sites in forested parts of Amazonia characterized by dense vegetation,” he adds. “It can also document the smallest surficial earthen features in the recently opened pasture areas.”