When the first Spanish explorers charted the Amazon rainforest, they claimed they saw many bustling and advanced cities holding millions of people (circa 1500). About 100 years later when the next wave of explorers charted the area, they found nothing but endless jungle.

In 2018 researchers found dozens of ancient Mayan cities hidden beneath the dense jungles in Guatemala using LiDAR. The archaeological application of LiDAR uses IR beams to scan the jungle from above. Differences in vegetation density indicate manmade structures since less vegetation grows on manmade structures. The LiDAR data is collected via differences in laser return times and wavelength. The buildings indicated that at least 10-15 million people lived in this very inhospitable location. The Mayans terraformed the landscape completely draining swamps and transforming the dry and nutrient-deficient soil by enriching it with biomatter. They even built massive moats and trenches around their cities to protect them from invaders.

When the Spanish came, they brought with them smallpox. And the idea is that this devastated the indigenous populations in America so quickly that the jungles overtook these abandoned cities before the Spanish could even find them. And so they dormant for hundreds of years.

The point is, is it possible those first Spanish explorers in the Amazon weren't actually full of shit?