In short:
Archaeologists have discovered the oldest-known scene of figurative art depicting a hunting scene.
The researchers used a new technique to date the artwork to about 51,000 years.
What's next:
Even older artwork around the world may be revealed using the new dating technique.
The red-pigment scene painted on the cave wall depicts human-like figures, some of whom are wielding spears or ropes, alongside much larger creatures that resemble pigs or cloven-hoofed mammals.
Preserved in the clean, still atmosphere of a cave on the south-west peninsula of the Indonesian island of Sulawesi, the rock art has been dated as being at least 51,000 years old.
It's the oldest-known example of storytelling art by our species, Homo sapiens, in the world, according to an international team of archaeologists and geochemists, led by Adhi Agus Oktaviana of Griffith University.
Their discovery, unveiled today in the journal Nature, also provides the clearest evidence yet that modern Homo sapiens used art to tell stories tens of thousands of years before findings of ancient art in Europe.
"Storytelling is a hugely important part of human evolution, and possibly even it helps to explain our success as a species," Griffith University archaeologist Adam Brumm and a co-author on the paper said.
"Finding evidence for it in art, especially in very early cave art, is exceptionally rare."
Some figures in the paintings carry the suggestion of being a "therianthrope" — a figure that combines attributes of human and animal.
"Archaeologists are very interested in depictions of therianthropes in the archaeological record, because it provides evidence for the ability to imagine the existence of a supernatural being, something that does not exist in real life," Professor Brumm said.
Australian National University archaeologist Susan O'Connor, who was not involved in the study, said the paintings "clearly communicate a narrative scene about ritual, myth or supernatural ideas and were designed to communicate these ideas to the viewers".
The cave rock art is also the earliest evidence of Homo sapiens' presence in the region, which is known as Wallacea.
"These dates are a few thousand years earlier than the earliest dated occupation found on the southern [migration] route in Flores or Timor," Professor O'Connor said.
New dating technique
The oldest artwork was discovered in a cave called Leang Karampuang in a limestone outcrop in the Maros-Pangkep region, where a number of other paintings have been previously found.
Rock art in another cave, known as Leang Bulu' Sipong 4, in the same area was dated at 43,900 years old in 2019.
The research team used a dating technique which overcame the unique challenges of accurately establishing the age of such ancient cave rock art.
Before the new study, scientists calculated the age of limestone or calcium carbonate artworks using a method known as uranium/thorium dating.
As water drips down cave walls and over paintings, the mineral calcium carbonate builds up like tree rings, locking elements such as uranium inside.
Over time, two types of uranium, called uranium-234 and uranium-238, decay into thorium at a steady and known rate.
So scientists would extract a core of calcium carbonate rock wall close to the artwork, dissolve the entire core in solution, and determine the ratio of uranium 234/238 and thorium 230 in the sample.
That ratio is then used to calculate how old the calcium carbonate around the painted layer is, giving an estimate of the age of the art.
The problem with calcium carbonate formations in caves is that it doesn't always form in neat layers.
The mineral also grows in small formations called "cave popcorn", in which the layers are curved and distorted, which can make cross-sectional samples less precise.
The new method used a laser to vaporise hundreds of micrometre-sized samples across a cross-section of calcium carbonate layers, then analyse the uranium-to-thorium ratio in each sample.
This builds up a much more accurate picture of the age of the various calcium carbonate layers.
This technique for dating limestone has never been used before, study co-author and Southern Cross University geochronologist Renaud Joannes-Boyau said.
"The idea is that we create a map of the sample so we understand where the layers are, and then we can actually select the right layers [to calculate a more accurate age]."
Using this technique, the scientists estimate the Leang Bulu' Sipong 4 painting is least about 4,000 years older than previously thought.
Art in Australia and elsewhere
Archaeometrist Adelphine Bonneau, from the University of Sherbrooke in Canada, said the technique analyses many data points from across each sample.
This means it is better at excluding outlying dates that might result from contamination from other minerals such as clays, which can get incorporated into the calcite layers.
While the Leang Karampuang painting reports to be the oldest confirmed rock art by modern humans in the world, that's likely to change as the new laser-based dating technique is used on rock art elsewhere, Professor Bonneau — who was not involved in the latest study — said.
For example, she said, engraved ochre estimated to be around 70,000–80,000 years old has been found in Africa.
"Why not have rock art that would be that old somewhere else in the world?"
A piece of ochre found in Arnhem Land in Australia is believed to be more than 50,000 years old, but Professor Bonneau said the Aboriginal rock art in Australia was difficult to date using the uranium technique, which needs calcium carbonate.
"I'm pretty sure about it, that some of the Australian rock art are even older than that, but unfortunately, there's no possibility about applying uranium series because there's no calcite layers," she said.
Radiocarbon dating also can't be used because the age of the rock art is at the very limit of what such techniques can date.
Professor Joannes-Boyau noted the style of the rock art bore some resemblance to rock art in the Kimberley in Australia.
"So are we talking about the route of the first Homo sapiens arriving through South-East Asia and then painting, so were Aboriginal people responsible for that art; therefore, are they the one that invented figurative art," he said.
"This is a question that we can pose."
Professor Joannes-Boyau is keen to use the technique to date other cave rock art in the area, which have stylistic differences that suggest the art could have been done at different periods.
"We're going to apply this technique across all these and try to understand the evolution of the styles," he said.