Homo naledi infant skull discovery suggests they buried their dead

The skull of a small child belonging to a different human species has been found deep in a cave system in South Africa. The team that made the discovery has named the child Leti and believes the skull shows that the Homo naledi species buried their dead.

Leti’s skull was found in a narrow fissure that is almost impossible to access. For that reason, the team argues that the skull was placed there deliberately, as a form of funerary practice. Presenting their findings at a virtual press conference, the researchers said it is evidence that hominins have been performing funerary rights for hundreds of thousands of years – even hominins with brains much smaller than ours.

“We can see no other reason for this small child’s skull being in the extraordinarily difficult position,” said Lee Berger at the University of the Witwatersrand in Johannesburg, South Africa.

Berger and his colleagues have been exploring the Rising Star cave system in South Africa for several years. In 2015, they described Homo naledi, a new species of hominin, found in the caves. More than a thousand bones were found strewn over the floor of the system’s Dinaledi Chamber, which could only be reached by expert cavers able to fit through small spaces. H. naledi had some features that resembled modern humans, but in other respects it looked like an older species: in particular, its brain was small.

Two years later, the researchers found a remarkably complete H. naledi skeleton in another part of the cave, the Lesedi Chamber. They called the individual Neo. Crucially, the team also managed to narrow down how long ago H. naledi lived. The remains are only about 250,000 years old, meaning H. naledi existed at the same time as our species and other big-brained hominins like the Neanderthals – yet they retained features from species that lived millions of years earlier.

Meet Leti

In September 2017, the team was exploring deeper parts of the cave, beyond the Dinaledi and Lesedi Chambers.

Marina Elliott of Simon Fraser University in Burnaby, Canada, was one of the researchers who went in. The distance isn’t great – “It’s about 12 metres from where the Dinaledi material was originally recovered in 2013-14,” she said – but the journey is claustrophobically challenging.

Elliott had to first go through a room dubbed the Chaos Chamber. “There’s boulders that have fallen from the ceiling,” she said. “Then there’s a little bit of a drop into a crawlspace that just literally leads into a couple of small narrow passages.” These passages are only tens of centimetres across, so the researchers had to turn sideways and even partly upside-down to get inside.

In one such passage, about 20 centimetres across and 80 centimetres tall, the researchers found a small ledge. Sitting on the ledge were 28 fragments of skull and six teeth.

When the researchers brought the remains back to the surface, they realised they probably belonged to one individual. They named the individual Leti, from the Setswana word letimela, meaning “the lost one”.

The team has now described Leti, and the surrounding caves, in two papers. Two of the teeth were milk teeth and four were adult. The adult teeth weren’t worn, suggesting they had only recently emerged from the gums. Based on this evidence, “Leti was probably somewhere between 4 and 6 years of age,” said team member Juliet Brophy of Louisiana State University in Baton Rouge.

Leti probably dates back to the same time as the other H. naledi remains, said Tebogo Makhubela at the University of Johannesburg in South Africa, who was also involved in the work. “We are assigning the age based on the similarity of the geology in all these chambers,” he said.

“It is an absolutely amazing and remarkable site,” says Emma Pomeroy of the University of Cambridge in the UK. Having the skull of a child will help us understand how H. naledi individuals changed as they grew up. Such patterns of growth “are what distinguish humans and other related species,” she says.

Primitive funeral?

Right from the start, Berger has suggested that the H. naledi bones were placed in the Rising Star cave system deliberately, by other H. naledi, after they died. “I think it’s fair to say it was controversial in 2015 to say a small-brained, primitive-looking hominin might have been deliberately disposing of its dead,” he said. But, he argued, “there’s been no credible evidence against that original hypothesis”.

The discovery of Leti, even deeper into the cave system, adds to the evidence, Berger argued. On this reading, Rising Star is a H. naledi grave.

Other potential explanations seem unlikely, said team member Darryl de Ruiter of Texas A&M University in College Station. “There’s no indication of any carnivore activity: no tooth marks, no gnawing, nothing like that,” he said. That means it is unlikely other animals carried the bones into the caves. “There’s no indication that there’s a large-scale water movement depositing these things,” he added.

“I think it’s still not 100 per cent certain,” says Pomeroy. She says that carnivores and floods are unlikely, but argues there are other explanations. One possibility is that a group of H. naledi went into the cave, perhaps for shelter, but got lost and died inside. “It does look like this network where you could quite easily get lost and it would be hard to get out.”

Pomeroy adds that it is unlikely H. naledi were simply disposing of bodies in the cave, for instance to avoid attracting scavengers, because it is so difficult to get into, “especially if you’re trying to drag a dead body”. If they did take the bodies down there, a symbolic purpose seems more plausible than mere disposal – but there is no other evidence of symbolic behaviour in H. naledi. “It is a difficult one,” she says.

There is evidence that Neanderthals buried their dead as early as 70,000 years ago. They had larger brains than H. naledi, though. There is also evidence that other animals grieve – from apes and monkeys to orcas and elephants – but no evidence of them carefully placing bodies in caves or other burial sites.

How might H. naledi have carried the remains of their dead so deep? “Our geologists are fairly certain that these deep areas of the the cave have always been in the complete dark zone,” said team member Steven Churchill of Duke University in Durham, North Carolina. He said cavers sometimes come across living baboons in the cave, seemingly feeling their way around. “Which is probably a terrifying experience,” he says. Conceivably H. naledi did the same.

Alternatively, they may have used fire to light their way. “There are bits of charcoal in the cave, but nothing we’ve been able to firmly associate with the hominins,” said Churchill. But controlled fire use goes back 400,000 years, at least in Europe. Churchill said “it wouldn’t be surprising” if H. naledi could make flaming torches to light their way.

Journal reference: PaleoAnthropology, DOI: 10.48738/2021.iss1.64; DOI: 10.48738/2021.iss1.68

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