An engraving on the floor of a cave on Gibraltar may be an example of Neanderthal art, proof the early humans weren't the primitive brutes they have often been portrayed as, researchers say.
Artwork, as an example of abstract cognitive thought, has long been held as belonging only to modern human, not our early Neanderthal cousins.
The engraving, looking something like a grid for a game of tic-tac-toe, was found in Gorham's Cave located on the eastern shore of Gibraltar.
Previous research has confirmed Neanderthals inhabited the cave for thousands of years.
The symbols have been dated to 39,000 years ago.
The discovery reinforces the depiction of Neanderthals as more intellectually advanced and closer to modern humans than had long been thought, researchers say.
The findings "brings the Neanderthals closer to us, yet again," says Clive Finlayson of the Gibraltar Museum.
It joins recent discoveries that show Neanderthals hunted with tools, ceremonially buried their dead, painted their bodies with pigments and used personal adornments such as feathers, proof their level of culture has long been underestimated, he says.
However, whether they had the capability of symbolic thinking involved in creating art is still a matter of debate.
The position of the Gibraltar engraving within the cave, in an obvious visible location, means it would have been seen by anyone entering the cave, says Francesco d'Errico from the French National Center for Scientific Research.
"It does not necessarily mean that it is symbolic -- in the sense that it represents something else -- but it was done on purpose," he says.
It may have been a sign to visitors that the cave was already in use or was owned by another group of Neanderthals, he suggests.
Finlayson notes the rock carving is located precisely at the place where the orientation of the cave changes at a 90-degree angle.
The engraving could be like indicating an intersection, he says.
"I'm speculating, but it does make you wonder whether it has something to do with mapping, or saying: 'This is where you are.'"
Not all experts are in agreement about the significance of the engravings, however, and if they are in fact evidence of Neanderthal intellectual capacity.
University of Pennsylvania anthropologist Harold Dibble said the engraving, even if considered art, is not all that impressive.
"It takes more than a few scratches -- deliberate or not -- to identify symbolic behavior on the part of Neanderthals," he says.