PARIS (AFP) - It may be a symbol of the Internet age but scientists in South Africa have found an ancient hashtag scrawled on a piece of rock that they believe is the world's oldest "pencil" drawing.

The design, which archaeologists say was created around 73,000 years ago, pre-dates previously identified abstract drawings from Africa, Europe and South-east Asia by at least 30,000 years.

It was found by researchers inside the Blombos Cave, around 300km east of Cape Town, a site that contains evidence of some of the earliest instances of what humans today would call culture.

Previous expeditions to the cave found shell beads, engraved pieces of ochre and even tools manufactured from a rudimentary cement-like substance.

Among the artefacts was a small flake of silicate rock, onto which a three-by-six line cross-hatched pattern had been intentionally drawn in red ochre.

"Our microscopic and chemical analyses of the pattern confirm that red ochre pigment was intentionally applied to the flake with an ochre crayon," the team wrote in a study published on Wednesday (Sept 12) in the journal Nature.

They said the pattern appearing on the fragment may have originally extended over a larger area and could have been "more complex in its entirety".

Although there are far older known cave engravings, including one in Java that is at least half a million years old, the team of researchers said the Blombos Cave hashtag was the oldest known drawing.

"This reinforces the idea that drawing was something that existed in the minds of the hunter-gatherers," Dr Francesco d'Errico, a director of the National Centre for Scientific Research at the University of Bordeaux, told AFP.

While drawings such as the one unearthed in South Africa undoubtedly had a "symbolic meaning" Dr d'Errico said early humans "probably didn't consider them as art".