Ancient rock art is vulnerable to weathering, the bleaching effect of sunlight, vandalism – and microbes. Now scientists at Be’er Sheva’s Ben-Gurion University are teaming up with the Austrian Academy of Fine Arts to fight the scourge of bacteria eating ancient petroglyphs in the Negev desert and the Alps. Yes, the European mountain range.
The project aims to start with characterizing exactly which microorganisms are responsible for damaging the prehistoric rock art.
Which begs the question, how much damage do microorganisms actually do to engraved or painted rocks, compared with weathering? Anywhere, and in the Negev desert?
“We don’t know. It’s both,” explains the head of the Israeli team, Prof. Ariel Kushmaro. In fact, the microorganisms are intrinsic to the weathering process, he explains: “Weathering is a combination of physical and chemical conditions, such as temperature, water and so on, with biological processes – microbes that live on the rock.”
So, the collaboration will begin with identifying the microscopic miscreants afflicting petroglyphs in the Negev and Alps, in order to better understand the process of how they decay rocks and, necessarily, the images.
It is true that rock art is found everywhere Homo sapiens set its feet. The earliest known painting was recently announced: a picture of a pig in Indonesia dating to 45,500 years ago. All is vulnerable to microbial mayhem, but the researchers will be confining their attentions to the open-air rock art in the Negev and Alps, i.e., not in caves or rock shelters.
The Negev is littered with petroglyphs, and there’s not much else we can say about it. “We do know that some is relatively new, because in places we have inscriptions in Arabic – one can date according to the style of the writing and letters,” Kushmaro explains to Haaretz. Hebrew graffiti etched onto the rocks isn’t unknown either. “But the older things, such as drawings of a hunter or animal, are very hard to date. There’s one of a hunter trying to hunt an ibex, which means that at the time there were ibexes in the area. It could be 3,500 or 5,000 years old. We don’t know.”
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Or even older. Some archaeologists believe the art was done by nomadic peoples predating the Bedouin. Art in the Alps is just as mysterious age-wise, but could go back thousands of years further, to the start of the Holocene.
Mean green micro machine
Kushmaro comes to the project with the preconception that he knows how the process begins: with what may be the oldest creature on the planet – cyanobacteria.
They live right there on the rocks (because they live everywhere), peacefully photosynthesizing. There are many species of cyanobacteria and many survive beautifully in extreme conditions like those in the Negev, where the rock surface at midday can reach temperatures of 60 degrees Celsius (140 degrees Fahrenheit) and the humidity is extremely low. At night it’s cool and humid, relatively speaking, which fazes them not. Cyanobacteria are known to thrive in desert environments too.
To be clear, the cyanobacteria don’t live on the baking surface of the rock per se, but a few millimeters below the surface, Kushmaro explains. They penetrate micro-cracks and slowly cause the upper surface to peel off, over decades and centuries, which is part of the weathering process. So the cyanobacteria would have been on the rock when the artists of yore began to carve, and would have entered the grooves very happily.
“We believe there are consortia of bacteria on the rocks, and believe that groups of cyanobacteria are the primary producers there,” he says. “They are the source from which everything starts; they’re the source of carbon; they fix carbon; they fix nitrogen from the environment; thus, they supply the needs of other bacteria.”
Asked whether the hardy cyanobacteria of the Negev don’t also support populations of fungi, he explains that they can do, and lichen, but that isn’t the case with the Negev petroglyphs. They’re concentrating on the bacteria, starting with cyanobacteria, which he feels must be the base.
The process is very slow, to be sure. Some of these petroglyphs are still discernible after thousands of years – though global warming is expected to accelerate the process, by the way, especially if precipitation picks up.
That begs another question, of what the collaborators hope to achieve vis-à-vis their goal of preservation. There are a lot of petroglyphs to preserve in the Negev and Alps.
First, Kushmaro points out that to treat a problem, one must understand it first, especially since unplanned preservation can actually cause more damage – for instance, using scotch tape to try to fit together ancient parchment fragments. Their work will, however, also be applicable to things like ancient monuments, which sounds like a more feasible preservation target.
Kushmaro warmly applauds Israel’s Science Ministry for digressing from its usual practice of financing projects in medicine, biotechnology, physics and so on, and agreeing to fund half the three-year cultural science project. (On the Austrian side, it’s being funded by the Austrian Science Fund.) The ministry’s goal is to establish international collaborations.
Asked how the scientists in Be’er Sheva entered into this relationship with Vienna’s Academy of Fine Arts, headed by Prof. Dr. Katja Sterflinger, Kushmaro explains that it began when Irit Nir, a doctoral candidate in biotechnological engineering, set out to study microbial weathering of petroglyphs and sought similar. People studying the microbial degeneration of rock art are not running around there in droves, but contacts were made and this collaboration ensued.