Homo naledi 'walked among us'

Ten days from now, when a new exhibition opens at Maropeng, scores of Homo sapiens will gaze through glass at the ancient bones of our "ancestor" Homo naledi.

Appropriately, this exhibition at the Cradle of Humankind will be called Almost Human.

Up until just a few days ago, it was believed this was the only way these two creatures could have faced off - one alive, one dead, one clutching a ticket to a museum, the other carrying silent secrets in its bones.

But as it turns out, there was a moment in history when they might have looked each other directly in the eye.

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This idea of us walking the earth at the same time as Homo naledi means reworking the gigantic puzzle of our ancestry.

It has also meant digging up some old bones of contention among our country's top scientists on whether Homo naledi buried their dead.

"If there is one other species that shared the world with 'modern humans' in Africa, it's very likely there are others. We just need to find them," said lead researcher Professor Lee Berger of the University of the Witwatersrand.

In a paper published in eLife this week, his team revealed that, at 335,000 to 236,000 years old, Homo naledi was vastly younger than originally believed and "likely lived alongside us".

And in two other papers also published this week there was still more to come: yet another remote chamber had been discovered in the same cave system where Homo naledi was first found.

And in it, additional specimens of the species "including a child and the well-preserved skull (and other parts) of an almost complete adult male".

The new findings have given the scientists renewed faith in their hypothesis that Homo naledi deliberately disposed of their dead.

This was one of the most astonishing claims made in 2015 after the 1,550 bones from the almost inaccessible Dinaledi Chamber in the Rising Star cave system had been researched.

Berger and his team said at the time they had explored every possible scenario which could explain the bones being in such a remote chamber and were finally "left with intentional body disposal as the most plausible explanation".

This "ritualised behaviour was previously thought to be unique to humans", they said.

But the biggest detractor of this theory, Professor Francis Thackeray - also at Wits - is still not convinced.

Last year, Thackeray published a paper in which he said that lichen detected on the bones of Homo naledi could not have grown without sunlight. This prompted his suggestion of a second, easier route into the caves along which live individuals made their way before a disaster possibly struck.

From his side, Berger said of Homo naledi's young age: "We can no longer assume which species made which tools, or take credit as a species for all the technological and behavioural breakthroughs recorded in archaeology in Africa."

One such behavioural breakthrough would have been the burying of the dead.

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Just like the Dinaledi Chamber, the newly discovered Lesedi Chamber is highly inaccessible.

Fellow researcher John Hawks, an anthropologist at the University of Wisconsin-Madison, said more Homo naledi bones in another deep cave "likely add weight to the hypothesis that Homo naledi was using dark, remote places to cache its dead. What are the odds of a second, almost identical occurrence happening by chance?"

But Thackeray is sticking with his theory that there were possibly other entrances to the chambers.

He "congratulates" Berger and his team on "another set of awesome discoveries" which he described as "thought-provoking".

But, he told the Sunday Times: "To my mind, it would still seem entirely possible that Homo naledi groups may have accessed chambers through routes that are now closed."

He said such routes may have also allowed for the penetration of light.

"Did Homo naledi deliberately dispose of its dead? I still say not necessarily. I think we still need to consider alternative explanations.

"We now know there were at least three openings in the Rising Star cave complex. We also know that dolomitic cave systems are dynamic," he said.

Thackeray also calls on the science community to keep open minds at a time when so many discoveries are being made.

"With a sense of humility, we do not have all the answers to a growing number of questions about the spectrum of human diversity through time."

farbert@sundaytimes.co.za