Tens of thousands of years ago in what is now Indonesia, a human made their mark by placing their hand upon a cave wall.
A new study from a team of Australian and Indonesian researchers say these faint ochre stencils are the oldest cave art yet discovered.
The research — published today in Nature — dates the art at a minimum age of 67,800 years old, making it over 1000 years older than the previous contender — etchings and hand stencils in a Spanish cave attributed to Neanderthals.
"This is … the earliest evidence we have for humans creating cave art of any kind, which is a really exciting discovery," said Adam Brumm, one of the senior authors on the paper.
"It's right on Australia's doorstep."
Professor Brumm, an archaeologist at Griffith University, said the location of the finding has implications for when the first humans made the journey into Australia.
"If our species was present there 67,800 years ago making rock art, it makes it considerably more likely that the evidence we find for humans in Australia by 65,000 years ago is correct."
But with a lack of corresponding archaeological evidence of the same age such as bones or fire pits, more research is needed to confirm our species lived in the region during that time period.
'A really old wall'
The ancient art is located in Liang Metanduno, a limestone cave on Muna Island in Indonesia.
The cave is a tourist destination well-known for cave paintings that are about 4,000 years old.
But behind these more recent drawings — including one of a chicken — the researchers found ancient cave art that was much older.
The art is two faint hand stencils, one with a minimum age of 60,900 years, and the other breaking the record with a minimum age of 67,800 years.
This puts it in the middle of the last ice age when sea levels were many of Indonesia's islands were connected, and Muna Island was joined to Sulawesi.
[datawrapper map]While the two art works are mostly worn away, the researchers were able to use digital tracing and other techniques to see the ancient paintings of the two hands.
Hand stencils, a common technique among early cave art, is where a hand is placed on the wall, and then a red pigment called ochre is blown or placed on top of it. When the hand is removed, like a stencil, it leaves an outline of the shape.
In this cave in Indonesia, the hands were then repositioned and ochre reapplied to form narrower, claw-like fingers: a technique unique to the region.
Several other younger hand stencils in this style were also found by the team at other caves around Sulawesi.
According to Maxime Aubert, an archaeologist at Griffith University and senior researcher on the new paper, while the team immediately knew it was interesting, they were not able to work out the age immediately.
"We didn't know what we had until we got to the lab, but we've been working on rock art in these regions for a long time," he said.
"The old rock surfaces are normally all gone … but in this cave you could see, it's a really old wall."
How to date cave art
To confirm their suspicions of age, the team investigated the calcium carbonate deposits that form on top of the painting, such as stalactites and stalagmites.
Professor Brumm says it was particularly difficult to date rock art around the world, and it was just lucky that the deposits in these limestone caves provided a way.
"These early people came along, made the cave art, and in some cases where we are very fortunate, geological features started to form naturally on top of the art," he said.
"They then provide a way that we can date the art itself."
Because the deposits grow on top of the art, Professor Aubert said the dates were likely to be an underestimate.
"It's possible that it could be a little bit older," he said.
As this particular type of dating method has relatively large uncertainty values, archaeologists commonly use the minimum age.
"Our bag of tricks for dating rock art is pretty light," Professor Brumm said.
"There's not really many other methods."
Research backs up early arrival of first Australians
Until now, efforts to find evidence of humans this old on Sulawesi have been particularly unfruitful.
According to Susan O'Connor, an archaeologist at the Australian National University who was not involved in the research, any other evidence for the same time frame — like cave art, bones or other evidence of humans — have eluded researchers.
"While modelling suggests that a northern route migration from Borneo into Sulawesi and hence to Papua is most likely, archaeological evidence was lacking," she said
"No archaeological sites even approaching the age of [65,000 years] have been found anywhere in the islands."
This has meant that some researchers have questioned evidence that humans were on the Australian continent around 65,000 years ago, and instead argue for a later date of around 50,000 years.
While the new research is just one piece of evidence of people in the region, it suggests occupancy at least 68,000 years ago, which helps strengthen the theory that Australia's first people arrived not long after.
Professor O'Connor said this new research would help "reconcile" the earliest dates of human occupation found in Indonesia and Australia.
"These paintings are clearly the oldest evidence of creative expression in the world — earlier than the rock art in Spain at Maltravieso attributed to Neanderthal," she said.
"This new dating of rock art in Sulawesi to at least 67,800 years old is incredibly significant both in terms of the global implications and in the context of the dating of earliest Australian settlement."
The team are continuing to look in the region for more evidence to strengthen the case for people living there at that time.
"Two years ago we went exploring further up that river. There's another limestone [area] there … we want to go back and do a big project," Professor Aubert said.
"There's something special happening in that region. Humans were really advanced and we know there's a lot more rock art there."
