Origins of modernity: Inside the Blombos Cave where the artefact was found. Picture: OLE F UNHAMMER
Origins of modernity: Inside the Blombos Cave where the artefact was found. Picture: OLE F UNHAMMER

The oldest known human-made art discovered to date — a 73,000-year-old cross-hatch design that looks like an oversized hashtag — has been retrieved from the Blombos Cave on the Western Cape coast.

The drawing was unearthed from sediments in the cave near Mossel Bay that have yielded a remarkable array of human-made artefacts, including engraved ochre, bone tools, spear points and shell beads.

The most recent find adds to the growing body of evidence that modern human behaviour emerged in Africa before our ancestors migrated to Europe. It is at least 30,000 years older than any other human-made art discovered so far.

"The conferences were all saying 20 years ago that the origins of behavioural modernity lay in Europe — in France, Spain and Germany because that was where there were markers like the rock art of the Lascaux Cave. The evidence from Africa at that stage was virtually nonexistent," says Wits archaeologist Chris Henshilwood, the lead author of a paper describing the latest Blombos Cave find published on Wednesday in the peer-review journal Nature. "But we now know people were already using symbols and language before they left Africa."

Arty fact: The Blombos Cave drawing with an ochre crayon on silcrete stone, thought be 73,000 years old. Picture: CRAIG FOSTER
Arty fact: The Blombos Cave drawing with an ochre crayon on silcrete stone, thought be 73,000 years old. Picture: CRAIG FOSTER

The drawing consists of a six-by-three cross-hatched design, made with a blood-red-ochre crayon on a flake of dark brown silcrete stone.

"These symbols were used repeatedly [in artefacts from the Blombos Cave] and are found all over the world. I don’t know what they [represented], but we are pretty certain they are symbols that meant something to the people who made them," says Henshilwood, who holds a research chair at Wits and is director of the Centre for Early Sapiens Behaviour at the University of Bergen, Norway.

"Once you can transfer an idea onto a rock or make a piece of jewellery, you are using symbols in a pretty advanced way, and must have pretty advanced language. We are looking at people whose brains were wired in quite similar ways to ours."

Henshilwood and his team have been involved in several other discoveries that challenge the idea that symbols first appeared when Homo sapiens (anatomically modern humans) entered Europe about 40,000 years ago and later replaced local Neanderthals.

For example, the oldest known engraving — a zigzag etched on a 540,000-year-old shell — was discovered in Trinil in Java; and 64,000-year-old paintings made by Neanderthals were recently found in caves in the Iberian Peninsula.

Blombos Cave has been under excavation since 1991 and contains material from two windows in time. The first is from a part of the Middle Stone Age between 100,000 and 70,000 years ago, and the second is from part of the Later Stone Age between 2,000 and 300 years ago.

These two distinct time periods are due to the fact that the cave was closed off by sand about 70,000 years ago when the sea level dropped, and then reopened when the sea levels began to rise again about 3,000 years ago, says Henshilwood. "It was essentially a sealed tomb."

As all the analysis of objects found is done in a laboratory, every item that is removed from the cave has its position recorded in 3D.

"We can reconstruct it and put everything back digitally," says Karen van Niekerk, principal investigator at Bergen University’s Centre for Early Sapiens Behaviour.

The hashtag-like drawing was dated from the age of the sedimentary layer in which it was found, using a technique called optically stimulated luminescence. This measures the amount of radiation that has accumulated in the grains of sand since they were last exposed to sunlight, before they were blown into the cave, Van Niekerk says.

The team first confirmed that the lines were ochre, and conducted a series of experiments to figure out how the drawing was made. They used a microscope to compare lines drawn with a pointed piece of ochre with a 1mm-3mm tip to lines that were painted onto silcrete — and then compared these with the original. They were able to figure out the direction of the lines on the original work from the location of tiny deposits of loose ochre particles in pits in the stone, and concluded the flake came from a larger grindstone, previously used to grind ochre, as some of the lines ended abruptly.

As is so often the case with archaeological discoveries, the scientists excavating the cave did not immediately spot the Stone Age hashtag, and it ended up in a bucket of seemingly insignificant material destined for further scrutiny in the lab.

Only much later did archaeologist Luca Pollarolo notice its potential significance as he painstakingly sifted through thousands of similar items, and sent a photograph to Henshilwood. "We had pieces of [etched] ochre 75,000 years old, beads covered in ochre in different styles, and engraved bone. The story was building, we even had ochre crayons, but we didn’t have a drawing," Henshilwood says. "This is another string in the bow to argue for modernity when we left Africa 60,000 years ago."