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1/ LIDAR is uncovering civilizations we never knew existed throughout the Amazon and other heavily forested areas. What is LIDAR, how does it work, and what’s it going to tell us? 
2/ LIDAR stands for LIght Detection And Ranging, it’s like RADAR, but uses lasers instead of radio waves. A LIDAR sensor sends out light pulses and detects when they return to the sensor. The known speed of light allows the distance of the reflecting surface to be calculated. 
3/ The output of a LIDAR sensor is a point cloud representing the 3D environment visible to the sensor. Some self-driving cars (e.g. Waymo) use LIDAR: 
4/ You can also slap Lidar on a plane to map the terrain and forests below. When mapping a forest your point cloud includes both the trees and the ground. 
5/ At first, this data looks just like the forest you would see with your own eyes. However, you can computationally subtract out the trees to see only the ground. This is how we are uncovering previously invisible structural remains from long-lost civilizations. 
6/ When Francisco de Orellana accidentally sailed the full length of the Amazon in 1541 he described seeing complex civilizations of hundreds of thousands of people on the banks of the river. The river’s namesake comes from a battle he had with a tribe of female warriors. 
7/ But when Europeans returned to the deep Amazon nobody saw these tribes and many thought Francisco was making it all up. For many years the “consensus” was that the Amazonian culture had always been quite primitive.
8/ However, LIDAR and other discoveries are changing this perception. There are multiple recent discoveries of previously unknown extinct urban/semi-urban civilizations in the deep Amazon. 
9/ One recent LIDAR survey uncovered the remains of a city with complex canal and irrigation systems, large structures, and other features previously unheard of in the Bolivian Amazon. www.nature.com/articles/s41586-022-04780-4 
10/ It is becoming clear that before Europeans arrived in South America there were complex civilizations in the Amazon. The “uncontacted” tribes we see in the occasional documentary are likely just the pitiful remains of a continent depopulated from disease that never recovered.
11/ Further evidence, like cliff drawings and human-made fertilized soil called Terra Preta are proving the existence of Amazonian human history dating back beyond 12,500 years ago! 
12/ But we have only begun to scratch the surface. The VAST majority of the Amazon has not been surveyed with LIDAR and it is almost certain that the most exciting discoveries are still in front of us. 
13/ Most of the secrets about humanity's past have yet to be discovered. But Archaeology is slow moving, underfunded, and increasingly political. We need fresh thinking and technological and economic innovation to accelerate the field.
14/ With the right people and the right support we can revive the spirit of discovery of the past! 
Cheers to @Graham__Hancock for making archaeology exciting for millions of people!
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Tuur Demeester @TuurDemeester
·
Nov 26, 2022
Great thread!
Hugo Nguyen @hugohanoi
·
Nov 27, 2022
great thread !