The entrance to the limestone cavern known as Cloggs Cave resembles the enormous door of a cathedral. Located on a cliff in South Australia, not far from the town of Buchan, Victoria, this same cave has attracted members of the Australian Aboriginal nation called GunaiKurnai for generations. Direct evidence of their visits is literally etched on the walls; the ceiling is now blackened by smoke from countless bonfires lit inside. Both 19th century ethnographic reports and the GunaiKurnai’s own oral traditions detail how the men and women who served as respected spiritual leaders of the “Old Ancestor” called “mulla-mullung” used the space for healing rituals, magic, and even curses.

These practices often involved burning native grasses, and their microscopic remains have now revealed how long Aboriginal people have been venturing into the cave. Based on detailed analysis in a study published today in the journal Frontiers in environmental archeologyHumans have depended on Cloggs Cave for at least 25,000 years.

“Here we show that the Ancient Ancestors selected entire grasses from the broader landscape and took them to Cloggs Cave to spread them in thin layers and burn them,” explained study co-author and Australian National University archaeologist Elle Grono. “Over time, sediments covered these burned layers, preserving each layer on top of another for thousands of years.”

The study’s co-authors also relied heavily on representatives of the GunaiKurnai community while conducting their fieldwork and consulted them during the analysis and dissemination of their findings. The key evidence came in the form of microscopic silica remains of plant tissues called phytoliths. While pollen is typically distributed by insects, animals, and wind, phytoliths typically remain where the plant decomposes. Because sunlight does not reach Cloggs Cave, the phytoliths inside almost certainly came from people or animals.

“We focused on half-burned phytoliths from ash layers, which can only have been brought by people, since the unburned ones could have arrived by any means,” Grono explained.

Carbon dating of phytoliths deposited in the top 73 layers of ash within a pair of excavation pits revealed plant burning within Cloggs Cave between 4,400 and 1,600 years ago. The team discovered 29 types of vegetation, from grasses and herbs to woody plants. The most common species belong to the Pooideae subfamily of grasses found in cold and temperate climates, as well as the Panicoideae Subfamily seen in warmer, humid areas. Many of these grasses were intentionally selected near the cave entrance, and almost a fifth of the phytoliths were melted or incinerated. Additional evidence from dated burned plants implied that local communities began bringing their materials to the cave 25,000 years ago.

One of the most surprising discoveries had to do not with plants, but with rocks. Inside one of the pits, archaeologists also excavated a standing stone nearly a foot tall that was likely used during ceremonies. This artifact was surrounded by ash from similar phytoliths.

“Their burning is consistent with traditional GunaiKurnai practices of using ashes to perform magic and rituals, and also to trace the footsteps of anyone who enters, including spiritual beings,” Monash University archaeologist Bruno David added.

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