Human and animal bones were found piled up in ancient caves. The cave is in the Umm Jirsan system, a series of lava channels beneath the Harrat Khaybar volcanic area in Saudi Arabia. Launching the Daily Star, the bones come from various types of animals, including cows, horses, camels, and rodents.

It is believed that the bones were prey for hyenas (Hyaena hyaena) and were there for 7,000 years. Seeing this, Dr Matthew Stewart commented.

"The lava channel was crowded with hundreds of thousands of preserved animal remains," said Dr Mathew Stewart, of the Max Planck Institute for Chemical Ecology, who authored the study in the area.

The lava channel was first discovered in 2007, but scientists refused to enter after hearing a growling sound from inside. Researchers from the Saudi Geological Survey, King Saud University, and the Max Planck Institute in Germany also collaborated and were desperate to enter the cave.

"42 percent of the bones had evidence of carnivorous processing, which included bite marks, gastric scrapes, and rounding from licks. There were dental cavities," says Steward.

"By studying the types of bone surface modifications, their frequency, and their location, we concluded that the bones at Umm Jirsan were carried by striped hyenas."

"Hyena are avid bone gatherers, which they transport to nests for consumption, feed to younger hyenas, or storage," he explains.

The study has reportedly been published in Archaeological and Anthropological Sciences.