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Pigs, Popcorn and the Origins of Prehistoric Art

Undated painting of a wild pig from a cave in Maros.

This undated painting of a wild pig from a cave in Maros, probably tens of thousands of years old, is one of the few surviving examples of animal depictions from the region. Credit: Kizen Riza

By Adam Brumm & Maxime Aubert

The discovery of 40,000-year-old cave paintings in Indonesia has changed our understanding of the origins of art and modern culture worldwide.

It is a strange thing to be able to hop off a motorbike, walk for a minute or two across a stubbly rice-field with the afternoon call to prayer booming from nearby village mosques, and stroll straight into a cave containing some of the oldest rock art in the world. It’s stranger still to think that only a short plane trip separates us from Australia to the south, and we are a world away from the so-called cradle of human creativity in Europe, where it has long been said that our species' ability to produce artworks of great skill and imagination first emerged about 40,000 years ago.

Not so long ago we had stood in this limestone cave on the Indonesian island of Sulawesi, staring up at a faded painting of a pig and a coloured outline of a human hand beside it, wondering if these were the oldest man-made images on the planet. Now, after a great deal of research in the field and lab we knew we were in the presence of something extraordinary: 40,000-year-old ice age art in the humid tropics of South-East Asia. This is the story of how we made this discovery.

Three years ago, one of us (Adam) travelled to the limestone hills of Maros, on the southern peninsula of Sulawesi, to carry out an archaeological dig in a cave. One Sunday, the team visited a nearby cave art site in Maros. The limestone cave is called Leang Jarie, which means Cave of Fingers, and it was not far from our base camp at the Bantimurung waterfalls, a popular tourist attraction best described as a riotous, butterfly-themed water-slide park.

With Indonesian archaeologist Budianto Hakim and his numerous students, we made our way to the Cave of Fingers just as it was getting dark. Switching on our torches, we saw that the interior walls and ceiling were covered with dozens of depictions of human hands. Prehistoric artists had made these images by pressing their hands against rock surfaces and spraying mouthfuls of red paint around them; when they took their hands away, negative imprints of them, known as “hand stencils”, were left behind.

The stencilled hands at Leang Jarie belonged both to adults and children, and probably men and women, although it’s difficult to be sure. Some are especially striking in that the fingers were modified to produce slender, ghostly forms. No doubt this is what gave the place its curious name.

The Maros caves are notable for their many hand stencils, as well as large life-like paintings of wild pigs, which are far more rare. This rock art was first reported in the 1950s, but it had never been dated and was largely unheard of outside Indonesia.

Archaeologists assumed that these images could not be more than a few thousand years old, as any earlier pictures would have deteriorated long ago in the tropical climate of Sulawesi. It had been suggested the art belonged to prehistoric farmers who settled in the region at about the time of the birth of Christ. At most it could have dated to 3000 years or so earlier, when a Mesolithic hunter-gatherer culture inhabited the caves. Either way, while interesting, it wasn't earth-shatteringly important.

We were keen to know the real age of the art because at our cave dig in Maros we had found tantalising evidence of art production, pieces of red ochre, in very old archaeological layers. Ochre is a natural earth pigment. In its raw form it consists of chunks of rock that can be ground into powder and mixed with liquid to make paint. Some of the excavated ochre pieces had been scraped to produce powder. Others looked like they were used like crayons.

The cave-dwellers were evidently doing something with ochre at least 30,000 years ago, if not earlier, and we suspected they were using it to make rock art. If so, the long-forgotten art of Maros could be immensely significant. Cave paintings this old would not just be a first in Indonesia, they would challenge everything we thought we knew about the origins of art.

The ability to make art sets us aside from the rest of creation. There is no human society that does not paint, draw, sculpt or otherwise produce art in some form or another, and no free-living animals engage in anything remotely resembling artistic activity. There is also no indisputable evidence that archaic and now-extinct human species, such as the Neanderthals, made art. The challenge facing archaeologists, therefore, is determining when and where this distinctively human trait arose.

In Africa, archaeologists have unearthed small pieces of ochre engraved with criss-crossed lines, which date to about 100,000 years ago. These markings were made by early modern humans and are by and large accepted as the oldest symbolic depictions. However, many archaeologists believe these objects reflect a precocious ability that did not become entrenched in our species until substantially later, when the first “true” art emerged in Europe.

Modern humans had left Africa and spread as far eastward as Indonesia and Australia by 50,000 years ago, and they first appeared in Europe about ten millennia later. The people who colonised these far-flung regions all shared a recent genetic history. It has long been argued, however, that they acquired very different cultures as they roamed across the vast Eurasian continent. For instance, the first Homo sapiens to arrive in Europe, a group known as the Aurignacians, are renowned for their flourishing artistic tradition. Aurignacian caves in France and Spain abound with stunning paintings of horses, mammoths, and other Ice Age beasts, as well as carved figurines of animals and people. In contrast, there have previously been no signs of similar artworks among the first modern humans to reach Asia and Australia, or even in Africa prior to the global exodus of our species.

This has led to the decades-old theory that the region now known for the bubonic plague, soccer and Eurovision was once the focal point of a crucial stage in the evolution of art and symbolic behaviour generally. It’s as though a creative “explosion” was ignited in the minds of our African forebears when they first set foot in Europe more than 40,000 years ago. The result was the invention of a complex suite of artistic skills that would eventually surge like a bow-wave across the rest of the world, and ultimately lies at the root of all modern human cultures.

This, at least, is the story that has dominated our textbooks for many years, but it has never been a particularly convincing one. First, it was quite obviously written by and for Europeans. This doesn't necessarily mean it is wrong, but we must certainly consider the bias inherent in a European-driven narrative that places Europe at the epicentre of a global revolution in human thinking. Second, the story is clearly built on shaky ground since the discovery of a single indisputable example of Aurignacian-aged art outside Europe would throw it into disarray. The long absence of any such evidence has made the story look sound, but that is why archaeology is so exciting: one new discovery can change everything.

This takes us back to Leang Jarie. It was on this Sunday visit that Adam, having crawled into a gloomy recess of the cavern and cast his torchlight across an extensive rock art mural on the low-hanging ceiling, made an interesting observation. Jutting out from the ceiling, and affixed to some of the hand stencils, were many small whitish-grey nodules that resembled miniature cauliflowers. These hard, odd-looking protuberances were up to 1–2 cm thick and wide, and stood out starkly against the reddish-purple paint of the stencils. In some cases the art had been almost completely blotted out by these things.

The peculiar forms seemed to be some sort of speleothem. Water in limestone caves contains soluble minerals that are left behind when the water evaporates. These minerals are essentially dissolved limestone and, when they accumulate in certain places, solid masses known as speleothems are born. Given enough time, water dripping from a single spot on a cave ceiling can create a huge hanging stalactite at that point, as well as an upright stalagmite on the floor below. These are two well-known types of speleothems, but there are many different kinds.

Having spotted several hand stencils covered with these growths it became evident that they might be the key to dating the artworks themselves. Speleothems contain trace amounts of uranium, which decays at a known rate into thorium.

By measuring the ratio of uranium and thorium within speleothems, a technique known as uranium-series dating (U-series), scientists can determine their age with remarkable accuracy.

The Leang Jarie hand stencils were clearly older than the speleothems that had formed on top of them. It stood to reason, therefore, that if we could date the speleothems we would have a minimum age for the art.

Back in Australia we examined the photos of the Leang Jarie hand stencils and identified the nodular objects, which are more commonly known as “cave popcorn”. These mini-speleothems form on the walls or ceilings of caves as water deposits thin mineral crusts that gradually build up into little popcorn-shaped nodes.

We were unaware of any prior attempts to obtain U-series measurements on popcorn as a means of dating cave art, but it seemed well worth a try, so we scratched together whatever funds we could spare from our own limited research budgets and set off for Sulawesi.

For several weeks we tore around Maros on motorbikes, dodging cows and chickens on the roads as we visited Leang Jarie and many other caves in search of the perfect popcorn. We were working with the local cultural heritage management authority based in Sulawesi's capital, Makassar, which is about an hours' drive from Maros. A senior researcher in this department, Muhammad Ramli, had a life-long interest in the Maros art and knew the best sites.

Maxime collected popcorn that had formed over rock art at seven cave sites, including Leang Jarie. Once we identified a promising sample we took photographs, made detailed notes and then removed a piece of the popcorn.

To extract a sample, four small cuts would be made around the edges of the popcorn using a rotary drill equipped with a diamond blade. The cuts went through the sides of the popcorn and into the rock face, enabling us to prise off a tiny portion of the wall or ceiling containing the art and adhering popcorn.

We only kept samples when we could see a paint layer overlaid by thin bands of the porcelain-like minerals comprising the popcorn. This showed that the popcorn grew on top of the paint, so the art must be at least as old as the mineral layers immediately above it. These were perfect for dating.

A pig painting and hand stencil from Leang Timpuseng.

Left: A pig painting and hand stencil from Leang Timpuseng. Dated at 35,400 years old and 39,900 years old, respectively, they are now the oldest known two-dimensional animal depiction and the earliest hand stencil in the world.

We collected 19 popcorns from 14 separate rock art images, including 12 hand stencils, a large painting of a pig and another of an unidentified animal (probably also a pig). The first pig painting is in a cave called Leang Timpuseng, and is so faded and obscured by popcorn that even the local archaeologists didn't know it existed. Right next to it is a hand stencil from which we also took a popcorn sample.

The pig seems to be a female babirusa. These animals, known as pig-deer, evolved from an archaic family of pigs and are found only on Sulawesi. The males have weird tusks that erupt from their snouts and curl back towards their eyes, and they look a bit like a cross between a midget hippopotamus and the gruffalo.

We took a popcorn sample from this pig painting and were especially eager to know its age. This is one of only a handful of animal images still surviving in Maros, and we were struck by its similarity to the animal art from Europe.

In the U-series lab at The Australian National University, Maxime set about dating the popcorn. With limited time available on the heavily booked machine, it was necessary to work 18-hour days and to sleep in his van outside the lab.

A huge amount of sample preparation was involved. Using a technique known as micro-milling, the popcorns were sliced through layer by layer in order to extract minute amounts of mineral powder from different depths, including directly above the pigment. These sub-samples were then dissolved in chemicals, and the resultant solutions run through the machine to measure the uranium-thorium ratios. Then the fun started.

Early one afternoon the machine began to churn out age results for the very first sample from Leang Jarie. Glancing over the data, Maxime nearly fell off his stool. This popcorn was really old! One after another the popcorn samples yielded similar estimates. Stunned, Maxime checked and rechecked the data, and then ran a series of tests to rule out potential sources of error.

But the outcome was always the same. All of the popcorns were more than 17,000 years old. The average age was at least 25,000 years, and the oldest was a staggering 39,900 years. Thus, the Maros rock art was compatible in age with the earliest dated paintings from western Europe, which had been considered the oldest known cave art in existence.

And it kept getting better. The most ancient sample from Maros, the Leang Timpuseng hand stencil, was now the earliest dated hand stencil on Earth.

The Cave of Fingers, which had kick-started this adventure, didn’t disappoint either. A hand stencil from here returned an impressive age of 39,400 years, and is the world's second oldest example of this widespread art form.

To our great surprise it turned out that the babirusa painting from Leang Timpuseng was at least 35,400 years old. This is equivalent in age to what was previously the earliest two-dimensional portrayal of the animal world, a rhino painting from France's Chauvet Cave.

The inferred time-depth of the Chauvet rhino is based on a radiocarbon date from the charcoal pigment used by the artist. This age is questionable, however, since it is possible that the image was made more recently using old charcoal from the cave floor. Our more accurately dated babirusa had thus stolen the crown. Our findings made the cover of Nature last October, and made headlines the world over. Science later ranked our study as one of the top 10 most important scientific breakthroughs of 2014.

We had thought that the idea of Europe being the global centre of art origins was such a fusty and enfeebled doctrine that our findings would be considered humdrum, but the revelation that it wasn't just early Europeans making cave art 40,000 years ago prompted a major backlash against the old Euro­centric wisdom. The authorities in this field (oddly, most of them Europeans) seized the opportunity to hammer away at a now crumbling edifice. The evolutionary roots of art are in Africa, they said, and cave painting was almost certainly invented there more than 60,000 years ago, long before our ancestors began their colonising journeys into Asia, Europe and other new lands.

Humans, in other words, were adorning caves with works of art for many thousands of years before they beheld the snowy mountains of France and Spain, or the smoldering volcanoes of Indonesia. Of course, there isn't a shred of evidence to support this theory, but it made huge waves in the popular media.

To coincide with the release of the rock art dates we held a press conference in Jakarta with Ramli and our other Indonesian colleagues. The response from the Indonesian media was overwhelming. Countless newspaper articles and TV stories followed, with the gist of most of them being, naturally: “Our culture is older than Europeans’”. This overlooked the fact that most Indonesians actually descend from Stone Age farmers who arrived in the region from Taiwan 5000 years ago. But given the nation's long history as a Dutch colony, and its emerging status as a global power, we thought this was fair enough.

The mood was even more jubilant among the people of Maros, who were delighted to see the name of their homeland “raised high” around the world. The team was feted in the local press, and we were formally thanked at our dig site by the mayor of Maros and a host of VIPs, including politicians and the heads of the police and military.

Standing there in the cave, shaking hands with army generals who had never before set foot on an archaeological site, it all seemed so unreal. The undreamed of significance of the Maros caves had now been revealed, and their days of being forgotten about were over.

This all goes to show the emotive power of prehistoric art, and why it is so important to determine its age. People yearn to understand what these images from our deep past really mean. While the tales we tell about this art are essentially all about us, in some ways that's not such a bad thing.

The evolution of art is no longer just a European story. It's now an Indonesian one. Later, with the advent of a great deal more rock art dating, and a lot of luck, it may become an Australian story as well, and an Indian story, an Arabian story, and so on.

Eventually, we may follow the trail back to Africa, where perhaps we will discover the real origins of our instinct for art. That will be a truly human story.

Adam Brumm is an Australian Research Council DECRA fellow in Griffith University’s Environmental Futures Research Institute. Maxime Aubert is an Australian Research Council DECRA fellow in Griffith University’s Place, Evolution and Rock Art Heritage Unit.

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