Ancient rock art's colours come from microbes

A particular type of ancient rock art in Western Australia maintains its vivid colours because it is alive, researchers have found.

While some rock art fades in hundreds of years, the "Bradshaw art" remains colourful after at least 40,000 years.

Jack Pettigrew of the University of Queensland in Australia has shown that the paintings have been colonised by colourful bacteria and fungi.

These "biofilms" may explain previous difficulties in dating such rock art.Professor Pettigrew 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"'Living pigments' is a metaphorical device to refer to the fact that the pigments of the original paint have been replaced by pigmented micro-organisms," Professor Pettigrew told BBC News.

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

"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," he told BBC News.

Speaking about African rock artists, he said that "they had an intimate knowledge of ingredients theye 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."

As such, Dr Bouakaze-Khan said it would be interesting to investigate whether the Bradshaw artists knew about the long-term effects of the specific pigments they used in their works.

via BBC News - Ancient rock art's colours come from microbes.