For centuries the Amazon has been regarded as one of the planet’s last vast, largely untouched regions, once home to small and dispersed communities. Yet today, a new international study dramatically revises this view.
Thanks to LiDAR technology, researchers have detected thousands of traces of a sprawling civilization that thrived in the forest’s southwestern portion between 600 BCE and 850 CE. Perfectly straight roads, monumental geoglyphs, and vast ceremonial centers narrate the story of the Aquiry civilization, which may have housed as many as three million people.
The discovery
The research, conducted by an international team led by the University of Helsinki, covered an area of about 183,000 square kilometers, equal to less than 3% of the Greater Amazon. Through aerial LiDAR scanning, capable of “seeing” the ground beneath dense vegetation, scientists identified remains of over 400 monumental sites perfectly preserved, along with numerous later settlements.
From these data, the researchers produced a conservative estimate that the entire region would have hosted more than 20,000 ancient ceremonial centers built with massive earthworks. The largest among those identified spans roughly 50 hectares.
Archaeological analyses and radiocarbon dating indicate that from the start of the first millennium until 850 CE the region was inhabited by between 1.25 and 3 million people. These figures challenge earlier estimates of the entire Amazon population and suggest the forest could have supported tens of millions of inhabitants.
LiDAR imagery also revealed a dense network of straight roads and large geometric structures, the famous Amazonian geoglyphs, linking the various political and ritual centers. According to indigenous oral traditions, these sites were intended for gatherings among communities, religious ceremonies, political decisions, feasts, athletic competitions, and collective rituals.
Although there were no stone buildings due to the region’s geology, the monumental earthworks testify to a remarkable level of social and territorial organization. The scholars also emphasize that Aquiry— the name used by indigenous peoples for the Acre River — was not a single kingdom, but a multicultural network of diverse communities united by political, economic, and ceremonial ties.
The importance of the discovery
Beyond the archaeological aspect, the discovery also profoundly shifts our understanding of the Amazon’s environmental evolution. The inhabitants of the Aquiry civilization altered the landscape on a large scale, transforming vast tracts of bamboo-dominated forest into fields of maize, manioc, and squash, while also managing numerous tree species deemed valuable.
Among these are the Brazil nut, the peach palm, and several fruit trees, today considered the product of a long interaction between humans and the environment. The presence and spread of these species demonstrate how the current Amazon rainforest was shaped, at least in part, by human activity developed over the centuries.
According to the researchers, this influence concerns not only biodiversity but also the carbon cycle and the functioning of tropical ecosystems. Understanding the role played by ancient populations could therefore help to improve future climate models and conservation strategies for the forest.
Still, the mystery remains about the disappearance of the Aquiry civilization around 850 CE, occurring in the same period as the rapid decline of Maya civilization in Central America.
