Homo naledi: Evidence of Cave Etchings and Burial Practices

A species of ancient human with a brain the size of a chimpanzee’s may have engraved symbols on cave walls and deliberately buried its dead. These new discoveries about Homo naledi, a supposedly primitive hominin, could potentially prompt a reconsideration of the origins of complex behaviors once thought to be unique to larger-brained humans like us.

“It’s a remarkable thing. My mind is blown,” says Lee Berger, a lead researcher at the National Geographic Society in Washington DC. “Much of what we thought about the origin of intelligence and the cognitive powers of having a big brain clearly just died,” he says, though other researchers who spoke to New Scientist question this view.

Homo naledi was discovered in 2013 in the Rising Star cave system in South Africa when two cavers squeezed through a tight passage into an unexplored chamber filled with fossil bones. In 2015, it was declared a new species. We now know that this hominin was around 144 centimeters tall and had a brain one-third the size of ours.

It is not yet known where Homo naledi fits in the hominin family tree, but its morphology suggests that its common ancestor with Neanderthals and modern humans dates back a million years or more. Fossil dating in 2017 showed that it lived relatively recently, from 335,000 to at least 241,000 years ago, potentially overlapping with Homo sapiens, which evolved in Africa around 300,000 years ago.

In 2021, the discovery of an infant skull in a narrow fissure indicated that Homo naledi deliberately interred its dead, suggesting the ability to control fire and navigate through dark passages. In December of that year, evidence of extensive use of fire in the Rising Star cave system, such as soot, hearths, and burnt bones, was also announced by Berger.

Now, Berger and his colleagues have published more remarkable findings from the Rising Star caves.

The team discovered engravings in the caves in July of last year. Berger had to lose weight in order to navigate through rock passages as narrow as 17.5 centimeters. To his surprise, he found engravings on a natural pillar at the entrance of a passage connecting the Dinaledi chamber and the Hill antechamber.

On the walls, he saw deeply engraved geometric shapes, including squares, triangles, crosses, and ladder shapes. These engravings would have required significant effort to create, as the rock they were carved into is extremely hard.

“Seeing these symbols was entirely unexpected,” says Berger. “It was a moment of awe and surprise.”

Aside from the 47 individuals who had accessed the caves, there is no evidence of anyone else having been inside, leading the researchers to argue that Homo naledi must have made the engravings. However, these findings are preliminary, and further dating is needed.

Neanderthals and modern humans in southern Africa have previously been found to have created similar symbols thousands of years ago. If the engravings in the Rising Star caves were indeed made by Homo naledi, they could be much older.

Berger suggests that the effort put into engraving the hard rock indicates that the symbols held meaning for Homo naledi.

However, other experts are more cautious. “It is premature to conclude that symbolic markings were made by small-brained hominins, specifically Homo naledi,” says Emma Pomeroy at the University of Cambridge. “While intriguing, exciting, and suggestive, these findings require more evidence and analysis to support the substantial claims being made about them.”

Additionally, Berger’s team has provided new evidence of what could be deliberate burials in the ground, a different mortuary practice from the previous discovery of internment in niches. In the Dinaledi chamber, bone fragments and teeth from a single body were found in an oval-shaped area of disturbed soil. Another possible burial site in the Hill antechamber was also discovered, where bones and teeth fragments, mainly from a fetal-positioned juvenile, were found.

Although these findings are only preliminary, the researchers argue that the orientation of the bones and patterns of soil disturbance indicate intentional interment, potentially predating the earliest known human burial in Africa by 160,000 years.

Other experts are not yet convinced, suggesting that the bones’ fragmented state does not align with deliberate burial practices typically characterized by better preservation. Further analysis and research will be necessary to confirm these findings.

Remarkable Behavior

These new studies present a richer understanding of Homo naledi and its behaviors. “The evidence is impressive,” says Chris Stringer at the Natural History Museum. The discoveries suggest that Homo naledi engaged in remarkable behaviors, such as carrying carcasses into the caves and potentially using artificial lighting. These actions imply group organization and the existence of a distinct species with cultural practices.

“This is not something a single individual would have done; it must have been a group activity. And it has happened multiple times,” says Stringer. These findings raise questions about the development of large brains and what it means to be human.

Further research at the Rising Star cave system will be approached with caution to preserve the site. Berger emphasizes the importance of engaging the scientific community in exploring the space that was clearly significant to Homo naledi.

Reference: bioRxiv, DOI: 10.1101/2023.06.01.543133 and 10.1101/2023.06.01.543127