Ancient rock art alive with bacteria

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Researchers say the ancient ‘Bradshaw art’ rock in Western Australia has maintained its vivid colors because it is colonized by living bacteria and fungi.
Studies conducted by Jack Pettigrew and his colleagues at the University of Queensland showed that the rock art has kept its colors after at least 40,000 years.

The team studied 80 of Bradshaw rock artworks in 16 locations within Western Australia’s Kimberley region, concentrating on Tassel and Sash, two of the oldest known styles of Bradshaw art.

Analyses showed that many of them had signs of life, but no paint. The team dubbed the phenomenon “Living pigments.”

“‘Living pigments‘ is a metaphorical device to refer to the fact that the pigments of the original paint have been replaced by pigmented micro-organisms,” Professor Pettigrew told the sate-funded BBC.

“These organisms are alive and could have replenished themselves over endless millennia to explain the freshness of the paintings’ appearance.”

The team found that a black fungus belonging to the group Chaetothyriales was one of the most frequent inhabitants of the artwork and that the original paint might have had nutrients which “kick-started” a mutual relationship between the black fungi and red bacteria that often appear together.

Further research showed that the fungi provide the bacteria with water, while the bacteria provide carbohydrates to the fungi.

Professor Pettigrew says the finding can explain the difficulties in dating some rock arts which are combinations of ancient paintings and recent life.

“Dating individual Bradshaw art is crucial to any further understanding of its meaning and development,” he said.

“That possibility is presently far away, but the biofilm offers a possible avenue using DNA sequence evolution. We have begun work on that but this will be a long project.”

A rock art expert from University College London also said the study could be very helpful to archaeologists who consider the effects of life on art.

“It’s very interesting and very exciting what they’re showing – that there’s some microorganisms going into the pigments and not destroying them, which is usually what’s associated with the effect,” said Didier Bouakaze-Khan.

He added that like African artists, the Bradshaw artists might have also been aware of the long-term effects of the pigments they used in their works.

African artists had an intimate knowledge of ingredients they were using and knew how long they would last, the rate of decay and how dark they would go and so on – not necessarily them controlling it, but they were definitely aware,” he explained.

<<Editors notE>>
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