An advanced civilization thrived in the Amazon basin, unknown to the world: this revelation changes everything.

On the edge of the tropical forests of the Amazon, in northern Bolivia, lies a savanna known as Llanos de Moxos—this is a favored spot for researchers, including Umberto Lombardo from the Autonomous University of Barcelona. Previously, archaeologists believed that the soil in the Amazon basin was too poor to support a human population before the arrival of Europeans; however, new findings from scientists are changing this perspective, as noted by The Economist.

In recent years, the notion that pre-Columbian Amazonia was untouched has diminished: researchers have uncovered several lines of evidence indicating that humans inhabited this area and that certain tree species were transplanted. Nevertheless, for a long time, scientists struggled to comprehend the extent of this civilization and how many people it could sustain.

The new study led by Umberto Lombardo and his colleagues has provided proof that the idea of an "untouched pre-Columbian Amazon" was indeed mistaken. During their research, Dr. Lombardo and his team discovered evidence of large-scale hydraulic engineering as well as maize cultivation. All of this supports the fact that a significant number of people lived in this region long before Columbus arrived.

Llanos de Moxos is primarily flat and gets flooded for three to six months each year. However, some hills rise above the water level: trees grow there, and people live by constructing homes from the earth due to the lack of stone. The authors of the study note that remnants of some of these earthen structures can still be seen today.

The research findings reveal that there are hundreds of mounds covering a total area of 4,500 square kilometers; some of these mounds reach heights of over 20 meters and span 20 hectares—they are interconnected by embankment roads that extend for miles.

The authors of the study point out that these structures were built by people known to modern science as the Casarabe culture, which thrived for around 1,000 years. The scale of the earthworks of Casarabe suggests that there were many of them. This raises questions about how they were able to sustain themselves.

Dr. Lombardo's team utilized satellite imagery and LIDAR, which can peel away vegetation, to reveal the terrain beneath. Researchers discovered a system of channels and ponds near the mounds—it's believed that the channels diverted water from the savanna into the ponds during the rainy season. Later, the water was retained for cultivation during drier periods. The authors of the study believe that such a system would have allowed local settlements to engage in agriculture year-round.

The team also examined local sediments for pollen and phytoliths—microscopic silica structures that form in many plant tissues. The presence of pollen and phytoliths indicated that the Casarabe cultivated maize, nearly ruling out all other crops.

At the same time, scientists acknowledge that the population size of the local civilization remains unknown. The earthworks are indeed extensive, but they could have been constructed gradually by a small group of people over a long period. Estimating how much maize was produced—and how many people it could support—will require further field studies. Additionally, it will be necessary to identify the varieties of maize cultivated, as they would not have been as productive as modern varieties.

According to co-author Eduardo Neves from the University of São Paulo in Brazil, recent attempts to estimate the pre-Columbian population of the Amazon basin have reached figures of 8-10 million people. However, scientists admit that this is merely "well-founded speculation."

The Casarabe themselves remain enigmatic. Stone axes and ornaments made of copper and lapis lazuli indicate trade with the Andes and what is now Brazil. Various burial practices—some more elaborate than others—suggest a social hierarchy. The most colossal mounds may have held special religious significance or been associated with political power.