"It brings Neanderthals even closer to us," said Professor Clive Finlayson, the director of the Gibraltar Museum and coordinator of the international team that carried out the research.
"It talks of high cognitive mental capacities in Neanderthals which are equivalent to humans."
The findings were published in the journal Proceedings of the National Academy of Sciences of the United States of America.
The paper, "A rock engraving made by Neanderthals in Gibraltar," was authored by a team that included specialists in the Neanderthal field such as professors Joaquin Rodriguez-Vidal, Francesco d'Errico and Francisco Giles Pacheco.
"The production of purposely made painted or engraved designs on cave walls is recognized as a major cognitive step in human evolution, considered exclusive to modern humans," the authors wrote.
D'Errico, of the French National Center for Scientific Research (CNRS), called it "the first example of cave art, an abstract representation made by Neanderthals and deeply engraved in the rock in a part of the cave they lived in."
The carving, discovered after years of excavation at Gorham's Cave, was eventually found beneath a Neanderthal sediment level that was itself discovered below a modern human sediment level.
It was the first area of bedrock that was exposed by the researchers, suggesting there may be other engravings yet to be discovered.
- 'Not a casual mark' -
Researchers also tried to learn how Neanderthals might have made the engraving.
They used stone Neanderthal tools to show that each groove required consistent, repetitive strokes in a single direction.
"To produce one of the grooves required 60 strokes, always in one direction," Finlayson said, adding that the whole of the etching required up to 317 strokes.
"We were immediately showing that this was not a casual mark. This required effort."
The engraving was found in the farthest reaches of Gorham's Cave, located in a cliff overlooking the Mediterranean Sea, where previous evidence suggests Neanderthals retired to rest.
"If there's going to be a place where you're going to have spare time to do these things, it's going to be there," Finlayson said.
It is by no means the first study to find that Neanderthals were closer to our species than previously thought.
Close examination of the same cave in Gibraltar revealed that Neanderthals may have caught, butchered and cooked wild pigeons long before modern humans became regular consumers of bird meat, a study earlier this month said.
Other recent studies have shown that in addition to meat, Neanderthals ate vegetables, berries and nuts, that they took care of their elders and used sophisticated bone tools.
An enigmatic branch of the human family tree, Neanderthals lived in parts of Europe, Central Asia and Middle East for up to 300,000 years but vanished from the fossil record about 30-40,000 years ago.