Written by Phin Upham,

For a long time, scientists believed that it would be impossible (or very nearly improbable) for groups of people to reside in the Amazonian rainforest. Not only was it difficult to mount an expedition to uncover any ruins, the poor soil quality seemed to hint that the food needed to support civilization simply could not have come from the jungle.

But the discovery of ancient roads and earthworks seem to suggest that a group of people once thrived there. Those seeking further proof need only look at the ground. The secret was a treatment the natives gave to the land that turned the ground black.

So called “terra preta” is a black soil with bits of charcoal and Columbian pottery mixed in. Archaeologists estimate that the soil was made over 2500 years ago, before the Columbians ever set foot in the jungles.

What scientists found about the soil placement was also telling. The groups seemed to prefer settling on bluffs overlooking rivers, or the Atlantic Ocean. Civilizations did exist in the western portion of the Amazon, near the Andes where runoff from the mountains brought minerals organically to the soil.

Skeptics argue that the evidence is inconclusive. The absence of terra preta does not mean the absence of civilization. Because the original findings came from heavily trafficked sites, it’s arguable that we merely weren’t looking for civilizations before we stumbled upon them.

How these civilizations thrived is still a mystery, but their food sources no longer have to be. It appears people did once live in the Amazon, but what the region looked like before we found it is an image thus far lost to time.

Phin Upham is an investor from NYC and SF. You may contact Phin on his Phin Upham website