Archaeologists Discover Ancient Cities Hidden in the Ecuadorean Amazon

Using laser scanning technology, researchers have found traces of 2,500-year-old cities in the Amazon rainforest. Complete with a complex network of farmland and roads, the discovery is the oldest and largest of its kind in the region.

Located in Ecuador’s Upano Valley, the dense system of pre-Columbian structures lies in the eastern foothills of the Andes mountains, according to a study published Thursday in the journal Science. Over 20 years of research preempted the find, but it wasn’t until the Ecuadorean government employed lidar—a remote sensing technology that surveys a landscape using lasers—that the ancient urban centers came to light.

“I have explored the site many times, but lidar gave me another view of the land,” archaeologist Stéphen Rostain, lead author of the study and director of research at the French National Center for Scientific Research (CNRS), tells Live Science’s Jennifer Nalewicki. “On foot, you have trees in the way, and it’s difficult to see what's actually hidden there.”

Rostain knew from his many ground expeditions that laser imaging would reveal new structures, but he hadn’t predicted the scale of the results, reports Science News’ Amanda Heidt. Covering roughly 300 square kilometers (more than 100 square miles), images from the lidar survey revealed a landscape full of organized human activities: These included more than 6,000 rectangular earthen platforms, as well as agricultural terraces and drainage systems.

The researchers say these structures formed at least 15 distinct settlements, which were connected by a system of wide, straight roads. Co-author Antoine Dorison, an archaeologist at the CNRS, says this society’s complexity is especially evident in this web of streets, which were carefully constructed to cross at right angles rather than follow the landscape.

“The road network is very sophisticated,” he tells BBC News’ Georgina Rannard. “It extends over a vast distance; everything is connected.”

Per a statement from the researchers, the sprawling complex was likely occupied by people from the Kilamope and Upano cultures from about 500 B.C.E. until 300 to 600 C.E. The residents were probably focused on agriculture, growing corn and sweet potatoes.

“It’s a gold-rush scenario, especially for the Americas and the Amazon,” Christopher Fisher, an archaeologist at Colorado State University who has scanned sites in the Americas but was not involved in this research, tells Science News. “Scientists are demonstrating conclusively that there were a lot more people in these areas, and that they significantly modified the landscape. … This is a paradigm shift in our thinking about how extensively people occupied these areas.”

Previously, scientists assumed that ancient South Americans “lived nomadically or in tiny settlements in the Amazon,” writes BBC News, but researchers estimate the newly discovered cities housed a population “in the 10,000s if not 100,000s.”

In recent years, lidar has been a vital tool for discovering traces of ancient Amazonian cities. Aerial laser sensing bypasses the forest’s density—which complicates and lengthens mapping by expedition—to create more accurate maps in a fraction of the time. As Fisher told Smithsonian magazine’s Brian Handwerk in 2022, the technology has proved “transformative for archaeology.” It’s helped uncover pre-Columbian settlements in the forests of Bolivia, Brazil and Belize.

At the beginning of his career, Rostain was discouraged from doing research in the Amazon, because most scientists assumed that no ancient groups of this scale had lived in the rainforest, he tells BBC News. He did it anyway and is now “quite happy to have made such a big discovery.”

That discovery is now “another vivid example of the underestimation of Amazonia's twofold heritage: environmental but also cultural, and therefore Indigenous,” write the researchers in the study. “We believe that it is crucial to thoroughly revise our preconceptions of the Amazonian world.”

Sonja Anderson | READ MORE

Sonja Anderson is a writer and reporter based in New York City.