Experiment reveals the chemical changes undergone by artefacts found in caves inhabited by bats

In an experiment to understand better how ancient artefacts are altered by the sediment in which they are buried for thousands of years, Australian archaeological scientists buried bones, stones, charcoal and other items in bat guano, cooked it, and analysed how this affected the different items.

The researchers, UOW PhD student Conor McAdams, and his supervisors, Associate Professor Mike Morley (Flinders University) and Distinguished Professor Richard “Bert” Roberts (UOW, Director of the ARC Centre of Excellence for Australian Biodiversity and Heritage), are seeking to expand our knowledge of the first modern humans to arrive in Southeast Asia.

“Our bat poo experiment might seem like mad science, but it is helping to fill gaps in the story of the peopling of Southeast Asia over the last tens of thousands of years,” Mr McAdams said.

The bat guano experiment was inspired during an archaeological dig at Con Moong Cave, one of the most significant archaeological sites in Vietnam, with a history of occupation that began more than 42,000 years ago.

While excavating a section of the cave floor they discovered a thick layer of ancient, soaking wet bat guano. Since caves once occupied by our human ancestors are often also occupied by bat colonies at different times, it is not uncommon for any archaeological artefacts they contain to be buried in guano-rich sediments.

In tropical regions, bats often live in much bigger colonies as there is generally more biomass. That means there is a tendency for bigger guano deposits to form. The bat guano in Con Moong Cave is almost 4-metres thick.

“We wanted to understand what the environment was like, thousands of years ago, in Con Moong Cave,” Mr McAdams said.

“We also wanted to understand how that environment might have changed, and whether archaeological remains might have been destroyed as a result of those changing environments, or the presence of bat guano.

“Bat guano is important when interpreting archaeological caves, because it is known to become acidic and destroy archaeological materials. But it also forms phosphate minerals, which can be useful as environmental indicators.”

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