Archaeologists were shocked to discover that a series of camels carved into desert rock faces in northwestern Saudi Arabia are actually prehistoric, dating from 7,000 to 8,000 years ago—before either the Pyramids of Giza or Stonehenge were built.

Experts suspected the ancient artworks were about 2,000 years old when they first discovered the reliefs in 2018, dubbing it the Camel Site. (There are similar ones at the ancient site of Petra in Jordan, which dates to approximately 300 B.C.)

Dating the heavily eroded carvings—which, unlike cave paintings, don’t contain the organic materials used for radiocarbon dating— presented a considerable challenge.

But a team of 14 scientists from Europe and the Middle East used X-ray analysis and luminescence dating to study the Camel Site in detail, reports Haaretz. They also evaluated erosion patterns, analyzed tool marks, and tested animal bones in related rock layers.

The Camel Site in Saudi Arabia’s northwestern al-Jouf province, with a carved sculpture of a camel’s legs seen in the foreground. Photo by Fayez Nureldine, AFP via Getty Images.

The luminescence dating method measures the energy of photons released by rocks to determine how long they have been exposed to naturally occurring infrared and thermal radiation. That can reveal when a geological structure was first exposed to sunlight or intense heat. But it was the tool marks, which suggested a stone implement rather than a metal one, that provided the first hint that archaeologists were in uncharted territory.

What researchers found was that the camels are actually the world’s oldest-known large-scale animal reliefs, according to a paper published in the Journal of Archaeological Science. That also makes the camels the first three-dimensional Neolithic carvings ever found.

“They are absolutely stunning and, bearing in mind we see them now in a heavily eroded state with many panels fallen, the original site must’ve been absolutely mind-blowing,” the paper’s lead author, Maria Guagnin, of the department of archaeology at Germany’s Max Planck Institute for the Science of Human History, told the National.

The Camel Site in Saudi Arabia’s northwestern al-Jouf province, with a carved sculpture of a camel’s legs seen in the foreground. Photo by Fayez Nureldine, AFP via Getty Images.

There are 21 carvings on three rock spurs. Each would have taken about 10 to 15 days to complete using tools made from a rock called chert—which would have meant sharpening and replacing the implements frequently.

“Neolithic communities repeatedly returned to the Camel Site, meaning its symbolism and function was maintained over many generations,” Guagnin told Live Science, noting that the carvings were regularly repaired by ancient peoples.

Though today the camels sit amid an arid, sandy desert, the location would have been a grassy plain with lakes back when their creators first began shaping the rocks. (At the time, camels hadn’t yet been domesticated.)

The images contain references to mating (the camel’s bulging necks and round bellies), suggesting that the reliefs may have symbolized fertility, or have been connected to the cycle of the annual wet and dry seasons.