Once upon a time, in the dim recesses of a cave in what is now northern Spain, an artist carefully applied red paint to the cave wall to create a geometric design—a ladder-shaped symbol composed of vertical and horizontal lines. In another cave hundreds of kilometers to the southwest another artist pressed a hand to the wall and blew red paint around the fingers to create a stenciled handprint, working by the flickering firelight of a torch or oil lamp in the otherwise pitch darkness. In a third cave, located in the far south, curtainlike calcite formations were decorated in shades of scarlet.

Although nothing of the artists themselves remains to establish their identity, archaeologists have long assumed cave painting was the sole purview of Homo sapiens. Another group of large-brained humans, the Neandertals, lived in the right time and place to be the creators of some of the cave art in Europe. But only H. sapiens had the cognitive sophistication needed to develop symbolic behavior, including art. Or so many experts thought.

Now dates obtained for the images in these three Spanish caves could put that enduring notion to rest. In a paper published in 2018 in Science, researchers report some of the images are far older than the earliest known fossils of H. sapiens in Europe, implying they must have instead been created by Neandertals. The findings open a new window into the minds of these oft-maligned cousins of ours. They also raise key questions about the origin of symbolic thought, and what, exactly, distinguishes H. sapiens from other members of the human family.

The dating results come as a vindication long in the making for Neandertals, who have had an image problem ever since the early 1900s, when French paleontologist Marcellin Boule famously reconstructed a Neandertal skeleton from the site of La Chapelle-aux-Saints in France as an apelike brute. In the decades that followed scientists discovered that Neandertals were much more like us physically than Boule had surmised. They also found Neandertals and H. sapiens made the same kinds of stone tools for millennia—but the bad rap stuck.

For a long time arguably the most significant point of distinction between Neandertals and modern humans seemed to be Neandertals did not make or use symbols. Whereas H. sapiens left behind jewelry, sculptures and cave paintings—all products of symbolic thought—no such items could be unequivocally attributed to Neandertals. In recent years, however, evidence for Neandertal symbolic behavior has been accumulating from sites throughout Europe. In Gibraltar a Neandertal engraved a hashtag symbol in the bedrock of a cave. In Croatia Neandertals harvested eagle talons and made them into necklaces. At sites in Gibraltar and Italy they hunted birds for their feathers, perhaps to wear as ceremonial headdresses and capes. In Spain, they made shell jewelry and mixed sparkly paint that they may have used as a kind of cosmetic. In a cave in France Neandertals erected semicircular walls of stalagmites, possibly for some ritual purpose. The list goes on.

Still, a key form of symbolic expression appeared to be missing from the Neandertal repertoire: rock art. The spectacular cave paintings of woolly rhinos, mammoths and other ice age animals at famous sites such as Chauvet and Lascaux in France, among other examples, were all linked to early modern humans. In the absence of any unambiguous evidence to the contrary, scientists assumed all cave paintings everywhere were likewise the handiwork of H. sapiens.

But in 2012 researchers led by archaeologist Alistair Pike, now at the University of Southampton in England, made a discovery that challenged this assumption. The team dated dozens of paintings from caves in Spain and found several that were rather older than previously thought. One image, a red disk in El Castillo cave, was found to have a minimum age of 40,800 years—old enough to possibly be the work of a Neandertal, and almost too old to be a modern human creation. (H. sapiens is not thought to have reached western Europe until around 42,000 years ago.) At a press conference announcing the 2012 findings, study co-author João Zilhão of the University of Barcelona declared any art from Europe that is found to be more than 42,000 years old must be attributed to Neandertals.

Six years later that day came. In the 2018 study Pike, Zilhão and their colleagues dated paintings in three caves located in different regions of Spain: La Pasiega in Cantabria, Maltravieso in Extremadura and Ardales in Andalucía. Although the caves contain a mix of figurative and nonfigurative images, the researchers focused their efforts on the latter variety. “We found in our 2012 study that the earliest dates we were getting were on red nonfigurative art—lines, dots, symbols and hand-stencils—so for [this] project we focused on paintings similar to these,” Pike explains.

As in the 2012 study, the team determined the age of the paintings using a radiometric technique called uranium–thorium dating, which is based on the radioactive decay of uranium into thorium over time. Specifically, the researchers obtained samples of the thin crusts of carbonate that have formed on top of the paintings and analyzed their thorium content to gauge the age of the crust, which provides a minimum age for the underlying painting. Their efforts were richly rewarded: The analyses show all three caves contain paintings dating to at least 64,800 years ago. Neandertals across Spain were thus making rock art more than 20,000 years before modern humans set foot in Europe.

Outside researchers praised the new study. “Wow!” says Genevieve von Petzinger, a PhD candidate at the University of Victoria in British Columbia whose research focuses on prehistoric symbols. She notes that when Pike and his collaborators raised the possibility of Neandertal artists in 2012, they got a lot of static from their peers who argued there was no reason to credit Neandertals over modern humans for the El Castillo images. “This is the mic drop,” Petzinger says of the newly dated paintings. “At 65,000, there’s no way it’s modern humans.”

Not only do the dates point to Neandertals making the art, they indicate Neandertals came up with these ideas on their own. When archaeologists first began uncovering signs of Neandertal symbolism, the evidence all came from the tail end of the Neandertals’ reign, by which point modern humans had established themselves in Europe. Some researchers posited that Neandertals were simply copying their modern human neighbors, possibly without really understanding what they were doing.

The new dates have convinced proponents of this idea otherwise. “I think that the most parsimonious explanation on current evidence is that it is Neandertals that must be making these representations,” says Thomas Higham of the University of Oxford in England, who has been dating sites across Europe to develop a chronology of the displacement of Neandertals by modern humans, and who was not involved in the new study. “I say that as someone who has long held the view that incoming modern humans, overlapping with Neandertals upon arrival [around] 45,000 to 40,000 years ago, were responsible for the late development of Neandertal symbolic behavior (perhaps a kind of 'imitation without understanding') just before their disappearance.”

Could the ancient paintings instead signal H. sapiens reached Europe earlier than the fossil record indicates? After all, recent discoveries elsewhere in the world have suggested our species originated and began spreading out of Africa thousands of years earlier than previously thought. “It’s possible,” Higham says, “but there is no evidence for it yet.”

If Neandertals had cave painting traditions, then researchers will need to grapple with the question of whether their behavior actually differed from that of modern humans in any meaningful way. One school of thought holds moderns were able to displace Neandertals by virtue of superior intellect and symbolic capabilities, including language.

Some experts have dismissed previous examples of Neandertal art, such as the Gibraltar hashtag engraving, as predictably unimpressive compared with the figurative art modern humans made. Von Petzinger disagrees. “When researchers joke about the sophistication of Neandertal art, I think they’re missing the point,” she says. “The big cognitive leap is making the graphic mark; it’s the ability to store information outside the body.” In a general sense, she says, the creation of abstract signs “marks the first step toward written language.”

“What is now needed is a wide-ranging analysis of other cave art using the same techniques to explore other potential cases,” Higham says. Pike and his team are looking to do exactly that. “Hand stencils dots and disks are found in caves all over Europe,” Pike notes. “We would like to start dating art outside Spain to see if Neandertal painting was as widely distributed as Neandertals were.”