London: Parts of the Amazon rainforests previously thought to be uninhabited may have been home to thriving populations of up to a million people, a study has found.
Archaeologists from the University of Exeter in the UK found the remains of fortified villages and mysterious earthworks called geoglyphs - man-made ditches with strange square, circular or hexagonal shapes.
Experts still do not know the purpose of these earthworks, as some show no evidence of being occupied. It is possible they were used as part of ceremonial rituals.
The evidence shows that there were hundreds of villages in the rainforest away from major rivers, and they were home to different communities speaking varied languages who had an impact on the environment around them.
Huge parts of the Amazon are still unexplored by archaeologists, particularly areas away from major rivers.
People had assumed ancient communities had preferred to live near these waterways, but the new evidence shows this was not the case.
The discovery fills a major gap in the history of the Amazon, and provides further evidence that the rainforest - once thought to be untouched by human farming or occupation - has in fact been heavily influenced by those who lived in it.
Archaeologists uncovered the remains in the current Brazilian state of Mato Grosso. By analysing charcoal remains and excavated pottery they have found a 1,800 kilometre stretch of southern Amazonia was continuously occupied from 1250 until 1500 by people living in fortified villages.
The experts estimate that there would have been between 1,000 and 1,500 enclosed villages, and two-thirds of these sites are yet to be found.
The new study shows there are an estimated 1,300 geoglyphs across 400,000 square kilometre of Southern Amazonia, with 81 found in the area surveyed as part of this research.
Villages are often found nearby, or inside the geoglyphs. They are connected through a network of causeways and some have been elaborately constructed over many years.
The earthworks were probably made during seasonal droughts, which allowed forests to be cleared. Drier areas still had fertile soils, where farmers would have been able to grow crops and fruit trees like Brazil nuts.
"There is a common misconception that the Amazon is an untouched landscape, home to scattered, nomadic communities. This is not the case," said Jonas Gregorio de Souza, from the University of Exeter.
"We have found that some populations away from the major rivers are much larger than previously thought, and these people had an impact on the environment which we can still find today," he said.
"The Amazon is crucial to regulating the Earths climate, and knowing more about its history will help everyone make informed decisions about how it should be cared for in the future," he added.
"We are so excited to have found such a wealth of evidence. Most of the Amazon hasnt been excavated yet, but studies such as ours mean we are gradually piecing together more and more information about the history of the largest rainforest on the planet," said Jose Iriarte, from the University of Exeter.
"Our research shows we need to re-evaluate the history of the Amazon. It certainly wasnt an area populated only near the banks of large rivers, and the people who lived there did change the landscape. The area we surveyed had a population of at least tens of thousands," said Iriarte.