The dark bowels of a limestone cave on Muna Island, off Indonesia’s Sulawesi coast, have just revealed an ancient secret.
There, a team of archaeologists discovered man-made rock art older than any other reliably dated example, with a minimum age of 67,800 years ago. The strange hand patterns with their pointed fingers are an important piece of the puzzle of early human migration into the region tens of thousands of years ago.
“What we’re seeing in Indonesia is probably not a series of isolated surprises, but the gradual unveiling of a much deeper and older cultural tradition that was simply invisible to us until recently,” archaeologist Maxime Aubert of Griffith University in Australia, who coordinated the research, told ScienceAlert.
“The amount and great age of the rock art found there shows that this was not a marginal or temporary site. Instead, it was a cultural area where early humans lived, traveled and expressed ideas through art for tens of thousands of years.”
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In recent years, both Sulawesi and the Indonesian portion of Borneo have emerged as unexpectedly important sites for understanding early human creativity and migration. In many cases, the cave paintings were discovered decades ago, but researchers lacked reliable methods to determine their age.
Thanks to advances in dating techniques, scientists now know that some of these artworks are much older than previously thought, with minimum ages exceeding 40,000 years and exceeding 51,000 years.
“Every time we apply these methods to new areas, the ages turn out to be much older than expected,” Aubert said. “This tells us that the problem wasn’t that early humans were suddenly making art in one place, but that we looked in the wrong places or didn’t look hard enough.”
This latest discovery was made in Liang Metanduno, a cave long known to contain ancient rock art. Aubert and his colleagues wanted to determine where the creations from this cave fit into the chronology of ancient art in the Indonesian archipelago.
Maxime Aubert in Liang Metanduno. (Ahdi Agus Oktaviana)
If the archaeologists are lucky, over a period of thousands of years, a thin layer of calcite is deposited over the art, precipitated by the water flowing over the rock surface. This water often contains a small amount of uranium, which is soluble in water. Over time, uranium decays into thorium, which is not soluble in water.
Because the rate at which uranium decays into thorium is precisely known, scientists can analyze the ratios of uranium to thorium in cover samples to determine how old it is.
This means that it was not the paint itself that was dated to 67,800 years ago, but the mineral crust that formed on top of it. Therefore, the underlying art must be at least that old.
And, combined with previous evidence, this suggests that much of the rock art in the region is potentially much older than previously thought, which in turn would change the way we understand Sulawesi – a key stopping point for early human migration into Australia.
Archaeologist Shinatria Adhityatama from Griffith University and the National Archaeological Research Institute of Indonesia works in the cave. (Maxim Aubert)
“Art may have become especially important as populations grew and groups interacted more often,” Aubert said.
“One way to think about this is through modern examples. Traffic lights are needed in big cities, but not in small villages. Similarly, shared art, symbols, and images may have helped people communicate identity, belonging, and shared meaning as social networks grew larger and more complex.”
For archaeologists, this type of symbolic behavior matters because of when and where it occurs. The newly dated art lies along a proposed northern migration route that early modern humans are thought to have taken as they moved across island Southeast Asia to the Sahul, the Ice Age landmass that once joined Australia and New Guinea.
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Finding evidence of complex artistic traditions along this corridor helps fill a long-standing gap between early sites in mainland Asia and the earliest traces of humans in Australia, and suggests that humans may have arrived on the Sahul as early as 65,000 years ago.
It also opens up many interesting questions, such as how much rock art of this era remains to be discovered in the surrounding area, how symbolic traditions traveled and spread, and whether there are even earlier chapters of this story to be discovered.
“What excites us most is that this art shows that early people in Southeast Asia were already expressing ideas, identity and meaning through images tens of thousands of years ago. These were not isolated experiments. They were part of a long-standing cultural tradition,” said Aubert.
“For us, this discovery is not the end of the story. It is an invitation to keep looking.”
The research was published in Nature.