Signs of life: excavations at Umm Jirsan Cave in Saudi Arabia

"Our results reveal repeated phases of human occupation of the site," the report's author said.

"Pastoralist (sheep or cattle farming) use of the lava tube and surrounding landscape is attested in rock art and faunal (animal life) records, suggesting that Umm Jirsan was situated along a pastoral route linking key oases.

"The excavation and survey work reveal repeated occupations… by Chalcolithic/Bronze Age, Neolithic, and possibly pre-Neolithic peoples over at least the past 7,000 years and perhaps for as long as 10,000."

By measuring isotopes, they found that herbivores primarily grazed on wild grasses and shrubs rather than being provided with fodder, while humans ate a high-protein diet.

Among the bones found were those of striped hyenas, dated back 7,000 years.

Providing shelter

It begins to paint a picture of life in this extremely hot and barren landscape of desert sands, where a traveller might have noticed—and been grateful for—a giant cave that could provide protection and shade for his caravan.

Here, they may have even found plants or water, since it is an area of well-developed wadi systems that feed into major oases. This recharges the aquifers and activates the springs.

The study, published in the journal PLOS One, suggests that humans used the cave intermittently as a shelter for up to 10,000 years. Although it was never a permanent residence, it was a saving grace for passing herders and their livestock.

Researchers also believe the cave likely played a role in hunting activities. Far from being an arid desert, in ancient times the region had lakes, rivers, and lush green areas, making it a haven for plants, animals, and humans alike.

Rich environment

Some settled here for extended periods, while others continued their migration. Over time, however, the environment changed, and the landscapes transformed, with the gradual desertification of the Peninsula.

Archaeological sites in northern Arabia confirm significant population growth during the Holocene, however, especially during the wet period around 10,600 years ago.

This saw the introduction of domestic cattle, the development of water management techniques, and oasis farming during the Bronze Age, facilitating settlement. Clues to settlement, such as pottery, have been found at different sites.

Hearth sites often associated with ancient lake deposits indicate long-term human presence in multiple areas, while researchers have also found circular and rectangular stone structures dating back 7,200 years, seemingly used for ritual purposes.

Speaking to Al Majalla, Stewart said the evidence confirms repeated settlement of Umm Jirsan for thousands of years.

The cave's features

The cave is accessible via three different entrances, but due to rock collapses, it was challenging to reach until 2017, when the SCTH built a wall and stairs at the main entrance.

The eastern passage of cave contains circular and rectangular stone structures, indicating past human use of the cave. Scientists also found fragments of human skulls within Umm Jirsan, "likely resulting from striped hyenas' ability to loot human grave sites".

In the study, a multidisciplinary team conducted a comprehensive survey and excavation in Umm Jirsan to assess visible archaeological materials, fossils, and sediments and identify potential areas containing sub-surface deposits.

Optically stimulated luminescence (OSL) was used to determine how long certain materials had been buried underground, with samples sent to a specialised laboratory at Royal Holloway, University of London. For radiocarbon dating, bone samples were sent to a laboratory in Scotland.

Adapting populations

Excavations near one of the cave entrances uncovered more than 600 animal and human bones and 44 pieces of stone tools, the oldest of which date back 10,000 years. The oldest human bone fragments date back 7,000 years.

Alongside those of striped hyenas, the remains included those of camels, horses, gazelle, ibex, goats, cattle, lizards, birds, hares, wolves, and donkeys, all in good condition despite the long passage of time.

Isotopic analysis shows that herbivores fed primarily on grasses and wild shrubs, implying reliance on natural (rather than cultivated) plants.

These findings also highlight the dietary adaptations of ancient human populations to changing environmental conditions and resource availability.

In addition, Stewart said the team found stone tools and rock art showing pastoral and hunting scenes. "At least six herding scenes were identified," the paper stated.

"This is notable as these are generally quite rare in the rock art of northern Arabia. At least one of the pastoral scenes also shows the use of dogs to herd a mixed herd of goats and sheep.

"The dominance of sheep and goat is significant, as they are rarely depicted in the rock art of northern Arabia, particularly in oasis settings such as Jubbah and AlUla."

Specialist software using algorithms that modify the contrast, hue, and colour of an image was used to enhance the visibility of the rock paintings and engravings.

Stewart thinks Saudi Arabia's caves and lava tubes are an untapped resource of biological and archaeological materials.

"By investigating these, we can fill significant gaps in ancient biological, environmental, and archaeological records."