Ancient human relatives buried their dead in caves, says new theory

By | June 5, 2023

In 2015, scientists reported a startling find from deep in a South African cave: more than 1,500 fossils of an ancient hominin species that had never been seen before.

The creatures, called Homo naledi, were short, with long arms, curved fingers, and a brain about one-third the size of a modern human. They lived during the time when the first humans roamed Africa.

Now, after years of analyzing the surfaces and sediments of the elaborate underground cave, the same team of scientists is making another sensational announcement: Homo naledi, despite their tiny brains, have buried their dead in graves. They lit fires to light their way along the cave and marked the graves with carvings on the walls.

Lee Berger, a paleoanthropologist at the University of the Witwatersrand in Johannesburg and leader of the project, said the discovery that a small-brained hominin did human-like things was profound. He suggests that big brains aren’t essential for sophisticated types of thinking, he said, like creating symbols, cooperating on dangerous expeditions, or even recognizing death.

This is Star Trek time, he said. You date, you meet a species, it’s not human, but it’s equally complex for humans. What are you doing? This is our moment, right now.

But a number of experts on ancient carvings and burials said the evidence doesn’t yet support these striking conclusions about Homo naledi. The cave evidence found so far could have a number of other explanations, they said. The skeletons may have simply been left on the cave floor, for example. And the charcoal and carvings found in the cave may have been left behind by modern humans who entered long after Homo naledi went extinct.

It seems narrative is more important than fact, said Maxime Aubert, an archaeologist at Griffith University in Australia.

Dr Berger will describe the findings at a scientific meeting on Monday, and three papers detailing the evidence will be published by the journal eLife. The studies are currently undergoing peer review, a spokeswoman for the journal said, and those reviews will be published publicly when they are finished.

The remains of Homo naledi were discovered in 2013 by two South African cavers exploring the rising star cave. Dr. Berger has organized an expedition into the complex system of chambers and tunnels, which stretches for miles underground.

When you’re there, it’s like you’re on a different planet, said Tebogo Makhubela, a geologist at the University of Johannesburg who joined the team in 2014.

The researchers found a large amount of bones, but reaching them required some risky caving. Some passages were so narrow that only the smallest members of the team could pass.

All told, the researchers found bones from at least 27 individuals. To Dr. Berger and his colleagues it seemed unlikely that they had simply washed up in the deep recesses of the cave.

In their 2015 report, the researchers suggested that Homo naledi brought the bodies there deliberately but left them on the cave floor instead of burying them, an act archaeologists call burial caches. It was still a provocative statement given what primitive Homo naledi looked like. Dr. Berger and his colleagues argued that the species belonged to a lineage that split from our ancestors over two million years ago. While our lineage has grown and acquired large brains, theirs has not.

Initially, scientists thought the fossils were evenly distributed across the floors of the chamber. But as they dug up more sediment in 2018, they observed two fairly complete skeletons rest inside oval depressions.

And it didn’t appear that the skeletons had formed the depressions by sinking into the sediment. For example, a layer of orange mud surrounded the ovals, but wasn’t inside them. Along the edges, the break looked clean.

This discovery, as well as other lines of evidence, have led Dr. Makhubela and his colleagues to now conclude that the remains were buried. They all seem to be painting the same picture, he said.

Until now, only humans were known to bury their dead, and the oldest known human grave dates back 78,000 years. Homo naledi lived much earlier. Dr. Makhubela said their fossils were at least 240,000 years old and could be as old as 500,000 years old.

Scientists also found fragments of charcoal, burnt bones of turtles and rabbits, and soot on cave walls near the fossils. They proposed that Homo naledi used hot coals to light the way in caves and brought wood or some other fuel to burn the fires. They may have cooked the animals as a meal, or perhaps as a ritual.

When these new discoveries came to light, Dr. Berger decided he had to take a look for himself in one of the chambers, known as the Dinaledi, which contained a supposed tomb. He had to lose 55 pounds before he could go through the pass. Last July he was ready to travel.

Dr. Berger went in alone and examined the fossils. As he left, he passed a pillar. On one side, he noticed a series of hashtag-like grooves etched into the hard surface.

Leaving was more difficult than entering. I almost died, Dr. Berger said, but escaped with a torn rotator cuff. Two team members, Agustín Fuentes of Princeton University and John Hawks of the University of Wisconsin, were waiting for him in the next room. Dr. Berger showed them the photos of the grooves he had taken.

The two scientists quickly went to their phones and came up with the same image: a cave carving in Gibraltar made by Neanderthals. It was strikingly similar to what Dr. Berger had just seen.

Based on the growing number of fossils scientists are finding in Rising Star, Dr. Fuentes said, it appears that Homo naledi may have visited the cave for perhaps hundreds of generations, moving together into the dark depths to bury their dead and mark the place. with the art.

This kind of cultural practice, he argued, would require language of some kind. You can’t do it without complex communication, he said she.

But Mara Martinn-Torres, director of Spain’s National Research Center on Human Evolution, said such speculations were premature based on the evidence presented so far. Hypotheses need to be built on what we have, not what we guess, she said.

Dr. Martinn-Torres considered the burial cache more likely than the burials, pointing out that the oval depressions did not contain complete skeletons in full alignment. If Homo naledi had brought the bodies into the cave and left them on the cave floor, the bones could have separated as the bodies decomposed. However, I think the possibility of having a burial cache with this antiquity is already staggering, he said.

I’m very optimistic that they have burials, but the jury is still out, said Michael Petraglia, director of the Australian Research Center for Human Evolution. Dr. Petraglia wanted to see a more detailed analysis of the sediment and other types of evidence before judging whether the ovals were burials. The problem is, I’m ahead of science, he said.

And Paul Pettitt, an archaeologist at Durham University in England, said it’s possible Homo naledi didn’t bring the bodies, either to hide them or to bury them. Bodies may have washed in. I’m not convinced the team proved it was a deliberate burial, he said.

As for the carvings and fires, experts said it wasn’t clear that Homo naledi was responsible. It was possible that they were the work of modern humans who entered the cave thousands of years later. The whole thing is nothing short of convincing, said Joo Zilho, an archaeologist at the University of Barcelona.

One way to test these possibilities would be to collect samples from the etchings, charcoal and soot to estimate their age.

Dr Hawks said these experiments were on the team’s to-do list, but could take years because there were so many samples to test. Rather than wait, Dr. Hawks said, the team decided to present its data now and strike up a conversation with other scientists about how to proceed.

For me, it’s much more important to document and share than to be right, Dr. Hawks said.

If the researchers are right, the findings will challenge some of the most important assumptions about human evolution. Humans and Neanderthals have brains that are enormous compared to those of earlier hominids, and paleoanthropologists have long speculated that larger size has great benefits. There should be some benefit to overcoming the problems, evolutionarily speaking, of having big brains. They require many more calories to feed, and a baby’s large heads put mothers at risk of death in childbirth.

One benefit of a big brain could be complex thinking. Neanderthals left behind an impressive record of cooperative hunting, tool use, and other skills. And modern humans create symbols, use language, and perform other intellectual feats.

If a hominin like Homo naledi could make carvings and dig graves, it would mean that brain size isn’t essential for complex thinking, said Dietrich Stout, an Emory University neuroscientist who was not involved in the studies.

I think the interesting question going forward is what exactly are big brains for, Dr. Stout said.

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