Researchers from University of Reading in the United Kingdom found that ring-like ditches in the Brazilian and Bolivian Amazon were much older than the rainforests currently covering these areas.
The study sought to find out whether the Amazonians did not alter too much of their landscape or if they did slash-and-burn farming after arriving in the rainforests.
John Francis Carson, lead author of the study and postdoctoral researcher at the University of Reading, and his team compared two cores present in the Bolivian Amazon. One of the cores came from a larger lake called the Laguna Oricore. The other came from a smaller lake, the Laguna Granja.
Analysis of the two cores revealed that the sediments that formed the ring-like ditches did not come from the rainforest, instead, 2,000 to 3,000 years ago, the Bolivian Amazon's ecosystem resembled Africa's savannah. Researchers wondered whether the early Amazonian forest was deforested or was barely affected by the human population that settled into it.
"The surprising thing we found was that it was neither," Carson told Live Science. "It was this third scenario where, when people first arrived on the landscape, the climate was drier."
During this time period, pollen came from grasses and fields had but a few trees. About 2,000 years ago, more trees started to grow in the area. Charcoal levels also decreased, lessening the risk and occurrence of fires.
While conditions were still similar to the African savannah, the early human settlement was able to dig the ditches before the forest grew and covered them. This discovery explained how the early Amazonians maintained the rainforest without any tools, the number of people involved in clearing parts of the forest, and their means of survival.
The study provided evidence that early Amazonians did not use any stone tools at that time, and fewer people helped in clearing the forest because it was not as dense as it is today. Also, the population thrived by growing maize.
This study had implications on modern-day forest management techniques, especially those in relation to nature and humans.
The study was published in the July 8 issue of Proceedings of National Academy of Sciences.