London: Researchers have found that a particular type of ancient rock art in Western Australia maintains its vivid colours because it is alive.
Some rock art fades in hundreds of years, but the ‘Bradshaw art’ remains colourful even after at least 40,000 years – thanks to microbes, reports a news channel.
Researchers have shown that the paintings have been colonised by colourful bacteria and fungi.
These ‘biofilms’ may now explain previous difficulties in dating such rock art.
Jack Pettigrew of the University of Queensland in Australia and his colleagues studied 80 of these Bradshaw rock artworks - named for the 19th-Century naturalist who first identified them - in 16 locations within Western Australia``s Kimberley region.
They concentrated on two of the oldest known styles of Bradshaw art - Tassel and Sash - and found that a vast majority of them showed 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“‘Living pigments’ is a metaphorical device to refer to the fact that the pigments of the original paint have been replaced by pigmented micro-organisms,” said Professor Pettigrew.
“These organisms are alive and could have replenished themselves over endless millennia to explain the freshness of the paintings`` appearance,” he added.
Among the most frequent inhabitants of the boundaries of the artwork was a black fungus, thought to be of the group of fungi known as Chaetothyriales.
Successive generations of these fungi grow by cannibalising their predecessors. That means that if the initial paint layer - from tens of thousands of years ago - had spores of the fungus within it, the current fungal inhabitants may be direct descendants.
The team also noted that the original paint might have had nutrients in it that ‘kick-started’ a mutual relationship between the black fungi and red bacteria that often appear together. The fungi can provide water to the bacteria, while the bacteria provide carbohydrates to the fungi.
The exact species involved in these colourations have yet to be identified, and Pettigrew said that the harsh conditions in the Kimberley region may hamper future research.
“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,” he added.