Authors of a study published Wednesday in PLOS One analyzed, plotted and 3D modeled these intriguing markings and compared them with other wall markings of all types to confirm that they are the organized, intentional products of human hands. The team also dated deep sediment layers that had buried the cave’s opening to reveal that it was sealed up with the engravings inside at least 57,000 and as long as 75,000 years ago—long before Homo sapiens arrived in this part of Europe.

This find, supported by the cave’s array of distinctly Neanderthal stone tools, identifies Neanderthals as the cave art creators and adds to growing evidence that our closest relatives were more complex than their dim caveman stereotype might suggest.

“For a long time it was thought that Neanderthals were incapable of thinking other than to ensure their subsistence,” notes archaeologist and study co-author Jean-Claude Marquet, of the University of Tours, France. “I think this discovery should lead prehistorians who have doubts about Neanderthal skills to reconsider.”

La Roche-Cotard is an ancient cave nestled on a wooded hillside above the Loire River. It was first uncovered in 1846 when quarries were operated in the area during construction of a railroad line. When it was first excavated in 1912, the array of prehistoric stone implements and cut-marked and charred bones of bison, horses and deer within revealed that Paleolithic hunters had frequented the site many thousands of years earlier.

Scientists first noted the finger tracings, with their organized appearance, as early as the 1970s. Beginning in 2016, the authors of the new study diligently plotted the various distinct panels and created 3D models for comparisons with other known examples of Paleolithic engravings. They also identified the cave’s many other wall markings made by the claws of animals, like cave bears, and by metal or other implements during modern incursions into the cave after 1912. Marquet says this process helped to show that the engraved panels were created in a structured and intentional manner. “These panels were not produced in a hurry, without thought,” he says.

The results also suggested that the designs were created by human hands, working the soft chalk wall, a material known as tuffeau, made of fine quartz grains and ancient mollusk shell fragments. The rock is permeable and covered with a fragile sandy-clay film.

“When the tip of a finger comes into contact with this film, a trace is left in the shape of an impact; when the tip of the finger moves, an elongated digital trace is left,” Marquet says. He knows this process firsthand. The team reproduced this method in a nearby cave made of the same type of rock. They marked walls using tools of bone, wood, antler and stone, as well as with their fingers, which produced engravings very similar to the ancient examples.

Co-author Eric Robert, an archaeologist at the National Museum of Natural History in Paris, says the graphics are impossible to interpret because they were made by a vanished people for viewing by their contemporaries.

“These images are not for us, and we do not have the keys to understanding their meaning, their possibly diverse and multiple functions,” he says.

Scientists know that the cave’s assemblage of discarded stone tools are of the Mousterian technology, sophisticated flake implements that are typically associated with Neanderthals. This suggests the cave was in use exclusively by Neanderthals, who in turn created the carvings on the walls. However, the authors note they can’t establish a direct relationship between those discarded tools and the engravings.

But another strong line of geological evidence comes from analyzing nearby sediments. During the Paleolithic, the Loire River, once closer to the hillside, flooded the cave numerous times and helped to carve out parts of it. Eventually those floods deposited thick sediments that, aided by erosion from wind and the hillside above after the river changed course, completely sealed off the cave. Clear evidence remains showing how layers of sediment were put down over the years, which would have completely covered the slope and cave entrance to a depth of more than 30 feet.

This covering persisted in place until 1846, when material was extracted for the railroad embankment, exposing the cave entrance. The sediments above and around the cave entrance, part of the layers that covered it before 19th-century excavations, were dated by optically stimulated luminescence dating, which can determine how long it has been since grains of sediment like quartz were exposed to daylight. A total of 50 sediment samples collected showed the cave was very likely sealed up at least 57,000 years ago, well before humans lived in this part of France. Previously, the oldest cave engravings attributed to Neanderthals were an abstract cross-hatching pattern found in Gorham’s Cave, Gibraltar, and dated to some 39,000 years ago.

Robert notes that several lines of evidence—the presence of Neanderthal tools, the geological evidence and the analysis of the engravings themselves—converge to demonstrate that the cave walls were adorned by Neanderthals.

“The authors present as convincing a case as can be made from a site disturbed by early excavations that the animal and human marks on its walls were left long before the arrival of our own species in Europe,” says archaeologist Paul Pettitt of Durham University in England, who wasn’t involved with the research. “Given that the cave’s archaeology is exclusively indicative of Neanderthals, with no evidence of subsequent Upper Paleolithic occupation, presumably because the cave was by this time inaccessible, this provides strong indirect, cumulative evidence that Neanderthals produced the finger markings.”

Humans from our family of ancestors began expressing themselves visually a very long time ago; Homo erectus carved zigzag patterns onto a shell more than half a million years ago. A series of handprints and footprints, which may have been deliberately placed by hominin children some 200,000 years ago, has been found on the Tibetan Plateau.

Neanderthals, or Homo neanderthalensis, may also be responsible for the world’s oldest known cave paintings. Pettitt was part of a team that found 65,000-year-old paintings in three Spanish caves that they attribute to Neanderthal artists. The early humans left red pigmented designs by drawing around their hands or pressing stained fingertips to the walls.

Examples of Homo sapiens’ very different style of cave art appear later. A purplish pig found on the walls of a cave hidden in a highland valley on the Indonesian island of Sulawesi was painted an estimated 45,500 years ago. If that date is correct, the Leang Tedongnge cave could be the earliest known work of figurative art, in which painters recreate real-world objects rather than producing abstract designs. The collections at Spain’s El Castillo cave and France’s Chauvet cave, where sophisticated lions and mammoths were painted perhaps 30,000 to 40,000 years ago, are notable early examples of this complex, figurative art that is unlike anything Neanderthals are known to have produced—at least so far.

But that distinction doesn’t necessarily mean that Neanderthal creations should be regarded as products of simpler minds or thought processes. Robert believes that comparisons between Neanderthal and Sapiens traditions aren’t necessary. For each species, he believes, the appearance of prehistoric carvings and paintings is less about when people were capable of making them and more about when social dynamics created a need for them at a specific time—even if those needs are a mystery to us today.