Neanderthals have gotten a bad rap. Informally, the now extinct human species Homo neanderthalensis is thought of as a bunch of babbling, rock-bashing meatheads. But more and more evidence suggests they were likely more sophisticated. Most recently, a piece of Neanderthal cave art was found in Gibraltar -- further evidence that modern Homo sapiens have been underestimating their ancestors intelligence.

The 39,000-year-old artwork -- found in Gorham's cave, overlooking the Mediterranean -- is little more than a series of criss-crossing lines, a sort of Neanderthal Twitter hashtag. But researchers say it's artwork, nonetheless -- deliberate and intelligent.

The artwork was studied by researchers from 11 different European museums and institutions. A number of experiments were performed to determine that the artwork was carved with Neanderthal stone tools and that the marks were purposeful.

"This engraving represents a deliberate design conceived to be seen by its Neanderthal maker and, considering its size and location, by others in the cave as well," wrote anthropologist Clive Finlayson, director of the Gibraltar Museum and author of a new paper on the subject. "It follows that the ability for abstract thought was not exclusive [to modern humans]."

"The pattern was clearly purposefully made, and not a utilitarian activity. There was a will to produce an abstract pattern," Finlayson's colleague Francesco d'Errico said.

The findings of Finlayson, d'Errico and their fellow researchers were published this week in the journal Proceedings of the National Academy of Sciences.