For 100 years, scientists thought these red marks were natural. Today, researchers say it is ancient art.

For 100 years, scientists thought these red marks were natural. Today, researchers say it is an ancient human art.

New analysis of red lines inside a cave in Wales suggests they were created deliberately by ancient humans around 17,000 years ago.

By Adam Kovac edited by Claire Cameron

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Curious red markings found in a UK cave, once thought to be geological and degraded features, are actually likely works of art made by prehistoric humansaccording to a new analysis.

The marks were first discovered in 1912 by two archaeologists, William Sollas and Henri Breuil, inside Bacon Hole, a cave in Wales located about 50 miles west of Cardiff. The cave itself was discovered in 1850. Later, an Iron Age bowl was discovered in the mud, along with bones that appeared to have been modified by humans, leading researchers to conclude that the cave had once been occupied by prehistoric humans.

Sollas and Breuil hypothesized that the ancient inhabitants of the cave may have made art. Together, the two men documented a dozen lines of red pigment that they believed were clear evidence of ancient human artwork. Indeed, they hypothesized that these marks were perhaps the oldest example of art dating from the Upper Paleolithic (around 50,000 to 12,000 years ago) in the British Isles.

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Others in the field, however, have considered these markings to be natural phenomena, such as iron oxide deposits, which also appear red. Subsequent archaeological research at the site has also been complicated by graffiti, and the site has largely been left alone by scientists – until now.

During a series of expeditions from 2022 to 2024, a team of archaeologists used high-definition photographs, color filter algorithms, spectroscopes and other high-tech tools to examine the marks. They compared samples of the marks with others taken from nearby rocks and iron oxide deposits and discovered that the marks were created using a pigment made from hematite, a form of iron oxide. The results were recently published in the review Quaternary. Photographic evidence revealed that the painted lines were arranged equidistant from each other, “indicating a deliberate, structured pattern,” the researchers wrote in the study.

The analysis suggests the marks were made at least 17,000 years ago, although scientists cautioned that further study would be needed to definitively determine their age. Even though the new estimate is off by a century or two, the results are a late vindication for Breuil and Sollas: “Horizontal lines (or streaks) represent anthropogenic activity,” write the authors of the new study.