Extinct human relative buried their dead 100,000 years before modern humans did, study claims

Controversial study claims that Homo naledi, an extinct human cousin with a brain one-third the size of ours, buried and maybe honored their dead.

The extinct human relative Homo naledi, whose brain was one-third the size of ours, buried their dead and engraved cave walls around 300,000 years ago, according to new research that is overturning long-held theories that only modern humans and our Neanderthal cousins could do these complex activities.

The data, according to some scientists, is insufficient to prove that H. naledi buried or remembered their deceased.

"I can see where they are connecting the dots with this data and do think it was worth reporting, but it should have been done with many more caveats," Sheela Athreya, an anthropologist at Texas A&M University who was not engaged inside the research, told Live Science in an email.

In South Africa's Rising Star Cave system, archaeologists made their initial discovery of H. naledi's remains in 2013. Since then, the 2.5-mile (4-kilometer) system has been home to more than 1,500 skeletal fragments from various individuals. Due to the remarkable preservation of their remains, H. naledi's anatomy is well known. They were bipedal creatures that stood around 5 feet (1.5 meters) tall and weighed 100 pounds (45 kilograms), had dexterous hands, a small but complex brain, and other characteristics that have raised questions about the complexity of their behavior. In a 2017 research published in the journal eLife, the Rising Star team hypothesized that H. naledi had purposely buried their deceased in the cave system.

In a news conference on June 1, paleoanthropologist Lee Berger, the Rising Star program lead, and his colleagues buttress that claim with three new studies, published Monday (June 5) on the preprint server bioRxiv, that together put forth the most substantial evidence so far that H. naledi purposefully buried their dead and created meaningful engravings on the rock above the burials. Peer review of the results has not yet taken place.

According to the new research, two small, oval-shaped pits on the floor of one cave chamber contained skeletal remains consistent with the burial of fleshed bodies that were covered in sediment before they eventually decomposed. These pits also contained skeletal remains. A solitary stone item was discovered in close proximity to the hand and wrist bones, suggesting that one of the graves may have possibly contained a grave offering.

In the news briefing, Berger stated, "We feel that they've met the litmus test of human burials or archaic human burials." The researchers' views, if adopted, would move Homo sapiens' previous record for the oldest evidence of intentional burial back 100,000 years.

The discovery of abstract engravings on the rock walls of the Rising Star Cave system also signals that H. naledi had complex behavior, the researchers suggest in another new preprint. It appears that H. Naledi, who sanded the rock before using a stone tool to engrave it, made these lines, shapes, and "hashtag"-like figures on specially prepared surfaces. The line depth, composition and arrangement imply that they were purposely produced rather than developed organically.

According to Berger, "There are burials of this species directly below these [engravings]," indicating that this area was an H. naledi cultural site. "They've intensely altered this space across kilometers of underground cave systems."

In a different preprint, anthropologist Agustin Fuentes of Princeton University and colleagues investigate the rationale for H. naledi's utilization of the cave network. "The shared and planned deposition of several bodies in the Rising Star system" and "the engravings" are indications that these people had a shared set of assumptions or beliefs about death and may have memorialized the dead, "something one would term'shared grief' in contemporary humans," they wrote. The new interpretations, however, have not completely won over other researchers.

"Tick marks on rocks could have been made by humans. That doesn't add anything to this discussion of abstract thought, according to Athreya.

There remain unanswered concerns regarding how H. naledi entered the Rising Star Cave system; many of the researchers' interpretations of significant behavior are predicated on the notion that it was challenging. Did they enter by the same entrance as us, or might there have been another way in? Jonathan Marks, a University of North Carolina at Charlotte anthropologist who was not engaged in the study, made this observation to Live Science. "This is a job for archaeology — lots of archaeology."

Read more about the findings from the National Geographic Society, which funded the research.