考古学：古代アマゾン文明の建造物を見つけ出す

The discovery of the archaeological remains of 11 previously unknown settlements of the Casarabe culture, which dates to around AD 500 to AD 1400, in south-west Amazonia are reported in a Nature paper. The findings represent a type of tropical low-density urbanism that was previously unknown in the Amazon, and suggest that western Amazonia was not as sparsely populated in pre-Hispanic times as previously thought.

Our understanding of the Casarabe culture, which developed between AD 500 and AD 1400 in Amazonia, has been restricted to evidence from a few isolated sites, as dense vegetation makes mapping tropical forests difficult. Therefore, our knowledge of the civic-ceremonial architecture of the major sites and of the regional organization of the Casarabe settlements has been limited.

Heiko Prümers and colleagues examined six areas within a 4,500-km2 region of the Llanos de Mojos, Bolivian Amazon, that belonged to the Casarabe culture. The authors used a technique called lidar (light detection and ranging), which allowed them to virtually ‘scrub away’ the dense vegetation to visualize the land and archaeology underneath the forest canopy. They found two large settlement sites, named Cotoca and Landívar, and 24 smaller sites, of which only 15 were previously known to exist. The authors generated a four-tiered hierarchical classification of the sites, based on factors such as the size of their earth platforms, the architecture on top of them and their canals and water reservoir systems. The structures included U-shaped structures, rectangular platform mounds and conical pyramids up to 22 metres tall.

The findings challenge current understandings of the pre-Hispanic history of Amazonia and improve our knowledge of ancient tropical civilizations in the Amazon.