It has always been assumed that the Amazon Rainforest was a pristine environment before we began major mining and logging practices in the 19^th century. However, new research is showing that mysterious ditches found scattered within the rainforest pre-date the rainforest itself.

These massive structures are up to 16 feet (5 meters) deep and sometimes just as wide. The big questions have to do with if and how much prehistoric people altered the landscape of the Amazon before the arrival of Europeans. The discovery that these could have been built before the forest grew answers several of these questions. They would not have needed stone tools or large numbers of people since there would have been no need to clear-cut the area first. It also provides an explanation for how these prehistoric people lived, by surviving on maize and other crops grown on the open land.

Shown here, a ring ditch next to Laguna Granja in the Amazon of northeastern Bolivia. Heiko Prumers

While researchers are still unsure of what the purposes of the rings were, if the use was for defense, drainage, water retention, ceremonial, or religious purposes, we are constantly finding ways to better understand the history of this unique environment.

Sediment cores taken from nearby lakes near the ditches took scientists by surprise when they saw that the oldest sediments didn’t come from a rainforest ecosystem but from a dry savannah. This tells us that the people who lived there at the time faced drastically different conditions that the ones we see today.

“It’s very likely, in fact, that people had some kind of effect on the composition of the forest,” says John Carson of the University of Reading in the United Kingdom. “People might favor edible species, growing in orchards and things like that, [or] altered the soils, changing the soil chemistry and composition, which can have a longer-lasting legacy effect.” While the earth’s natural cycles caused the conditions to grow the rainforest, people may have shaped the land for hundreds of years after that: “People have been affecting the global climate system through land use for not just the past 200 to 300 years, but for thousands of years.”

These kinds of studies can help us better understand how to better preserve the Amazon and how, if so, people can best coexist with the forest.

Read the original article on the Huffington Post.