Hundreds of ancient earthworks resembling those at Stonehenge were built in the Amazon rainforest, scientists have discovered after flying drones over the area.

The findings prove for the first time that prehistoric settlers in Brazil cleared large wooded areas to create huge enclosures meaning that the 'pristine' rainforest celebrated by ecologists is actually relatively new.

The ditched enclosures, in Acre state in the western Brazilian Amazon, have been concealed for centuries by trees, but modern deforestation has allowed 450 to emerge from the undergrowth. They were discovered after scientists from the UK and Brazil flew drones over last year.

The earthworks, known by archaeologists as 'geoglyphs' probably date from around the year zero.

The research was carried out by Jennifer Watling, post-doctoral researcher at the Museum of Archaeology and Ethnography, University of São Paulo, when she was studying for a PhD at the University of Exeter.