A 73,000-Year-Old 'Hashtag' Found in South African Cave Is the Earliest Known Drawing

Researchers have reported the discovery of the oldest known drawing in a cave on the southern coast of South Africa, according to a study published in the journal Nature.

The drawing, which takes the form of a simple, red, cross-hatched pattern made up of nine lines was found on a small piece of silcrete—a fine-grained rock formed from sand and gravel—unearthed in 73,000-year-old sediments from the Middle Stone Age.

Using microscopic and chemical analysis, an international team of researchers concluded that the pattern is not part of the stone and was intentionally drawn using a primitive pointed crayon made from red ocher—a natural clay earth pigment. This likely had a tip measuring between 1 and 3 millimeters in width, according to experiments conducted to recreate it.

The lines that make up the pattern terminate abruptly at the edges of the silcrete fragment, suggesting that it once covered a larger surface, and may have been more complex, although the researchers can only speculate as to what form it took originally.

According to the team, the drawing predates the earliest previously known drawings created by our species, Homo sapiens, by at least 30,000 years.

While the scientists didn't date the drawing directly—this wouldn't be possible—they did date the layer that it was found in, Karen L. van Niekerk, an author of the study from the Centre for Early Sapiens Behaviour at the University of Bergen, Norway, told Newsweek.

"There are no other drawings published from older contexts," she said. "So, for now, it is the oldest. I have no doubt that there might be even older drawings, but they have not yet been found."

Symbols, such as abstract and figurative drawings, are inherent to our humanity. Without them, language, writing, mathematics, art, religion, laws, and other features of human society could not exist.

"Abstract and depictive representations produced by drawing are a prime indicator of modern cognition and behavior," the authors wrote in the study.

The cave, which is located east of Cape Town, has yielded some of the earliest known evidence of behaviorally modern human cultural activity and indications of symbolic thinking.

Since excavations began there in 1991, researchers have discovered various artifacts—including shell beads, pieces of ocher with abstract patterns and innovative tools made from preheated silcrete—which date to between 70,000 and 100,000 years ago. Some of the ocher engravings, resemble those drawn on the piece of silcrete.

Together, these artifacts demonstrate the ability of early Homo sapiens in southern Africa to produce graphic designs of various media using different techniques, the study authors say.

Until recently, experts thought that unambiguous symbols first appeared when Homo Sapiens first entered Europe about 40,000 years ago. However, certain discoveries in the past few years suggest that the production and use of symbols emerged much earlier and was not confined to our species.

In a study published earlier this year, for example, researchers identified the world's oldest known cave paintings in Spain, revealing that they were created not by modern humans, but by now-extinct Neanderthals more than 64,000 years ago.

Furthermore, researchers announced the discovery of a shell featuring an engraved zig-zag pattern in sediment layers dated to 540,000 years ago on the Indonesian island of Java. It is thought that this symbol was created by Homo erectus—another extinct species of archaic human.

Blombos Cave drawing with ochre pencil on silcrete stone. Craig Foster

The Javan shell predates the recently reported cross-hatched pattern and differs from the ancient "hashtag" in the sense that it is an engraving not a drawing. The Spanish cave paintings are more recent than the latest find, although they are older than other prehistoric drawings created by our species.

As far as we know, there were no other hominids in southern Africa at the time when the cross-hatched drawing was made, so researchers can be confident that it was the product of our species.

This article has been updated to include additional comments from Karen L. van Niekerk.