A trio of papers posted online and presented at a meeting today lays out an astonishing scenario. Roughly 240,000 years ago, they suggest, small-brained human relatives carried their dead through a labyrinth of tight passageways into the dark depths of a vast limestone cave system in South Africa. Working by firelight, these diminutive cave explorers dug shallow graves, sometimes arranging bodies in fetal positions and placing a stone tool near a child’s hand. Some etched cave walls with crosshatches and others cooked small animals in what amounted to a subterranean funeral, more than 100,000 years before such behaviors emerged in modern humans.
If true, this scenario, based on a wealth of fossil finds in South Africa’s Rising Star cave system, would have major implications for the dawn of human behavior as well as the abilities of our extinct cousins, Homo naledi. “We are facing a remarkable discovery here of hominids, nonhumans with brains a third of the size of [modern] humans … burying their dead, using symbols, and engaging in meaning-making activities,” team leader Lee Berger, a National Geographic explorer in residence with an appointment at the University of the Witwatersrand, said at a press conference. “Not only are [modern] humans not unique in their development of symbolic practices, but [we] may not have even invented such behaviors.”
However, other researchers are overwhelmingly skeptical of the papers, which are in review at the online journal eLife and have been posted on bioRxiv. Researchers say they are wowed by the fossil finds, but the bodies could have simply fallen or been dumped into the pit and been buried slowly by natural processes. Later hominins could have made the etchings, which are undated.
“I am more and more persuaded that something amazing happened here,” given the wealth of skeletons, says paleoanthropologist María Martinón-Torres of the Spanish National Research Centre for Human Evolution. “But they have not met the test to show deliberate burial.”
Berger’s team made its first discovery in Rising Star in 2013: the bones of at least 15 individuals at the bottom of a chute 50 kilometers northwest of Johannesburg. The team named it a new species because it had a surprising mix of traits, such as a small brain and a globular skull. Researchers were also surprised by how recently it lived: sometime between 241,000 to 335,000 years ago, based on radiometric dates on sediments above and below the remains. As more bones emerged, Berger speculated they had been intentionally buried.
It was an explosive claim. The oldest widely accepted burial is of a modern human toddler dated to 78,000 years ago in a cave in Kenya, published in Nature in 2021 by Martinón-Torres and colleagues. Now, Berger says, he has evidence to prove his case.
In 2018, he was watching members of his team work in the caves, following the action by livestream because he was too big to crawl along the narrow passages to the chamber. Suddenly, the camera got bumped and went into infrared mode. In the black and white image, Berger could see the distinct edges of an “oval feature.” “I think it’s a grave,” he told the excavators. “They said no.”
Further excavation showed the oval to be a pit 8 centimeters deep and 50 by 25 centimeters in size, filled with 83 bone fragments and teeth from one H. naledi individual as well as a few fragments from other individuals. The bones were interspersed with orange-red stones, apparently from the layer below. Berger, who lost 20 kilograms to see the chamber himself, believes the stones show ancient gravediggers excavated the pit, digging up dirt and stones, setting them aside, and then using them to cover the body.
Elsewhere in the cave, the team found another set of very fragile bones. They removed two big chunks of sediment with bones inside, encased them in plaster, and took them to their lab. There, CT scans revealed 90 skeletal pieces and 51 dental pieces from three H. naledi individuals, including a child. The scans also revealed a tool-like stone object next to the child’s hand. The researchers argue that the arrangement of the bones suggests the bodies were carefully buried in a fetal or seated position.
They also discovered crosshatchings and other geometric shapes engraved on the cave walls; some were carved on top of others, indicating they were etched at different times. So far, the oldest undisputed symbolic art dates to 73,000 years at Blombos Cave in South Africa. But Berger, who planned to present the work today at the Richard Leakey Memorial Conference at Stony Brook University, argues that the undated etchings must be the work of H. naledi, as no other hominin left traces in the caves.
He also says that in order to work in the dark, H. naledi had fire, although the papers include no evidence for this. But hominins controlled fire elsewhere by at least 600,000 years ago. Berger has posted images online of charcoal and charred animal bones from the cave.
H. naledi had a brain of about 410 to 600 cubic centimeters, the size of a chimpanzee or Australopithecus brain. Taken together, the team’s scenario suggests “that those of us that teach and write about the evolution of social behavior … need to step back and take humans off the pedestal,” says co-author Agustín Fuentes of Princeton University. “Much of what we assumed was distinctly human, and distinctively caused by having a large brain, may not be [due to] either of those things.”
Evolutionary biologist Clive Finlayson of the Gibraltar National Museum agrees. “It’s not about brain size but how the brain is structured,” he says. He thinks the etchings were “most likely” the work of H. naledi because no remains of big-brained humans have been found in the cave. “It shows that Homo naledi had a level of self-awareness,” Finlayson says.
But others say the team’s evidence doesn’t support such leaps. “The whole thing is unconvincing,” says archaeologist João Zilhão of the University of Barcelona, who has proposed that Neanderthals made early cave art. He and others say natural processes could have positioned the H. naledi corpses. For example, the bodies could have been dumped into the chamber, or fallen or been washed in. Geologic movement and sedimentation, common in caves, could have moved the bones and covered them with dirt. The undated etchings, which resemble later carvings made by H. sapiens in South Africa, could have been made much later, adds archaeologist Paul Pettitt of Durham University.
At the moment, the data “sadly do not present a clear and unambiguous demonstration of a deliberate burial,” says Pettitt, who is an expert on ancient burials. He says the team needs to finish excavating the pits and further scrutinize the bones and sediments to determine whether they were laid down simultaneously in a burial or at different times, and whether the bodies were disturbed later by geological movements. Martinón-Torres adds that it’s unclear from the photos whether the bodies were laid down intact, as expected in a deliberate burial. “We don’t have articulated bodies,” she says.
Also missing is the wealth of fragmentary artifacts expected at a grave site, such as stone tools used to dig the pits. “There should be cultural debris that is typical of internments,” says archaeologist Curtis Marean of Arizona State University. “They are going to have a terrific struggle making an iron clad case for pits and burials, given the extremely challenging work environment,” he adds.
Researchers agree that by finding so many individuals of H. naledi, Berger and his team have uncovered a remarkable death scene. But without stronger evidence, H. naledi can’t be given credit for inventing meaning-making behaviors, Pettitt and others say. “It’s the hard science of excavation that’s impressive here,” Pettitt says. “We can and really should ignore speculation about Homo naledi’s apparent complex emotional intelligence and cognition.”