Detailed excavations of a Bolivian large mound known locally as Isla del Tesoro (Treasure Island) have revealed evidence of humans living in the region much earlier than first thought. Credit: Lombardo U, Szabo K, Capriles JM, May J-H, Amelung W, et al. (2013)

Researchers have discovered the earliest evidence yet of humans living in the Bolivian Amazon, putting the first known human habitation of the region at about 8000 years earlier than was previously thought.

The new finding, which centres on data gathered from middens in the often-flooded Bolivian grasslands, puts the date of the earliest known human habitation of the area at 10,400 years ago.

The study, published today in the journal PLOS ONE, involved excavation of three middens in the Bolivian Amazon that revealed layers of freshwater snail shells, animal bones and charcoal topped by newer layers containing human bones, bone tools and pottery.

Katherine Szabo, Principal Research Fellow at the University of Wollongong and a co-author of the new study, said that the finding showed these early human groups were able to adapt to difficult environments.

"It was a watery habitat, which has a major effect on the distribution of animals they would be hunting. Any humans groups living there necessarily would have to be really mobile as well," she said.

"Because it's such a difficult location, no one thought there would be early human occupation there. Other sites where evidence of human occupation had been found were close to coasts, river banks, forests and places with plentiful resources."

"What this is telling us about early inhabitants of South America is that they were very much more flexible and adaptable than perhaps we have given them credit for in the past."

The humans who helped build these middens lived in a time of changing climate conditions.

"This was just as the last ice age was ending, at a time of environmental flux and there was starting to be a lot more water on landscapes," said Dr Szabo.

"People were moving into new areas and the resources they relied on were changing."

The new find was an exciting insight into the time line of humans in South America, but "the prehistory of the Americas is still quite recent compared to Asia or Africa," she said.

Maciej Henneberg, Professor of Anthropological and Comparative Anatomy at University of Adelaide, said the new find was very interesting.

"The methods used are innovative and allow detection of archaeological sites previously difficult to notice," said Professor Henneberg, who was not involved in the study.

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This story is published courtesy of The Conversation (under Creative Commons-Attribution/No derivatives).

