An Australian archaeologist has helped uncover evidence of the earliest inhabitants of the Bolivian Amazon after scientists stumbled across traces of ancient poo.
The chance discovery came about when a team of researchers went to Bolivia to study the origins and geography of mysterious "forest islands", or built-up mounds in the grasslands of the country's Beni region.
What they ended up finding were the chemical remains of faeces from ancient nomadic hunter-gatherers dating back to the end of the last Ice Age some 10,400 years ago.
During excavations, Dr Umberto Lombardo of the University of Bern and his team found piles of freshwater snails, animal bones and charcoal in the mounds.
Further investigation of a large mound known locally as Isla del Tesoro, or Treasure Island, found the distinctive "chemical signatures" of human presence.
"It was effectively a poo signature," Associate Professor Katherine Szabo from the University of Wollongong told AAP.
Assoc Prof Szabo, a shell specialist who worked with Professor Mike Morwood in the cave where he uncovered the "Hobbit" skeleton on Indonesia's island of Flores, says the team found an elevated level of these chemical signatures indicating the presence of faeces throughout the sediments.
She said many of the bones had been burnt, most likely from cooking.
The scientists say the discovery indicates the humans from that time were nomadic, moving across the grasslands as they hunted mammals, caught fish and birds, and gathered snails.
Over time, the refuse built up to form the mounds which sit elevated above the floodplain.
More mounds are likely to be buried beneath, the scientists say.
Assoc Prof Szabo said the prehistoric discovery is even more incredible because the landscape of the low-lying desolate wetlands wasn't an ideal place for humans.
The research is published online in the open access journal PLOS ONE.