Yes, There Were Lost Civilizations In the Amazon

For a long time, the conventional wisdom was that the Amazon was inhabited by small tribes of hunter-gatherers from the time that the first modern humans arrived in the region, ca. 14,000 years ago until well into the post-Columbian period. But, increasingly, there is evidence of farming and moderate density sedentary settlements there that existed, at least on and off, for many thousands of years that collapsed with European disease and colonial impacts.

The one discussed below was one of at least several such civilizations in the Amazon. Another was contemporaneous in the Brazilian Amazon (see also here and here). A much earlier Amazonian farming civilization is discussed here. See also here (for ancient rice domestication and farming in South America).

Science News explains the new find in the Amazon made possible with aerial lidar surveys (see also the press release here): 

A massive urban landscape that contained interconnected campsites, villages, towns and monumental centers thrived in the Amazon rainforest more than 600 years ago. In what is now Bolivia, members of the Casarabe culture built an urban system that included straight, raised causeways running for several kilometers, canals and reservoirs. . . . 

Such low-density urban sprawl from pre-Columbian times was previously unknown in the Amazon or anywhere else in South America. . . . a substantial Casarabe population spread out in a network of small to medium-sized settlements that incorporated plenty of open space for farming. . . . 

Earlier excavations indicated that Casarabe maize farmers, fishers and hunters inhabited an area of 4,500 square kilometers. For about a century, researchers have known that Casarabe people fashioned elaborate pottery and constructed large earthen mounds, causeways and ponds. But these finds were located at isolated forest sites that are difficult to excavate, leaving the reasons for mound building and the nature of Casarabe society, which existed from about the year 500 to 1400, a mystery. . . . it is obvious that the mounds are platforms and pyramids standing on artificial terraces at the center of well-planned settlements. . . . 

These sites raise questions about whether only places with centralized governments that ruled over people who were packed into neighborhoods on narrow streets, such as 6,000-year-old Mesopotamian metropolises, can be defined as cities.

Some past urban settlements organized around crop growing spanned up to 1,000 square kilometers or more in tropical regions. These include locales such as Southeast Asia’s Greater Angkor roughly 700 to 800 years ago and interconnected Maya sites in Central America dating to at least 2,300 years ago. . . . Clusters of interconnected Casarabe settlements ranged in area from 100 square kilometers to more than 500 square kilometers. Spread-out settlements of comparable area include 6,000-year-old sites from Eastern Europe’s Trypillia culture. . . . 

Casarabe culture’s urban sprawl must have encompassed a considerable number of people in the centuries before the Spanish arrived and Indigenous population numbers plummeted, largely due to diseases, forced labor and slavery.

The paper and its abstract are as follows:

Archaeological remains of agrarian-based, low-density urbananism have been reported to exist beneath the tropical forests of Southeast Asia, Sri Lanka and Central America. However, beyond some large interconnected settlements in southern Amazonia, there has been no such evidence for pre-Hispanic Amazonia. 

Here we present lidar data of sites belonging to the Casarabe culture (around AD 500 to AD 1400) in the Llanos de Mojos savannah–forest mosaic, southwest Amazonia, revealing the presence of two remarkably large sites (147 ha and 315 ha) in a dense four-tiered settlement system. 

The Casarabe culture area, as far as known today, spans approximately 4,500 km^2, with one of the large settlement sites controlling an area of approximately 500 km^2. The civic-ceremonial architecture of these large settlement sites includes stepped platforms, on top of which lie U-shaped structures, rectangular platform mounds and conical pyramids (which are up to 22 m tall). The large settlement sites are surrounded by ranked concentric polygonal banks and represent central nodes that are connected to lower-ranked sites by straight, raised causeways that stretch over several kilometres. Massive water-management infrastructure, composed of canals and reservoirs, complete the settlement system in an anthropogenically modified landscape. 

Our results indicate that the Casarabe-culture settlement pattern represents a type of tropical low-density urbanism that has not previously been described in Amazonia.

H. Prümers et al. Lidar reveals pre-Hispanic low-density urbanism in the Bolivian Amazon. Nature. Published May 25, 2022. doi: 10.1038/s41586-022-04780-4.