Written in the stars, buried deep below...
CRANIUM FROM THE CAVE: The braincase of a male skull of Homo naledi measures just 560cm3 in volume – less than half that of the modern human skull pictured behind it. PICTURE: NATIONAL GEOGRAPHIC
They lay there completely alone. There was nothing with them except for an owl that found its way into their dark resting place… FOR HUNDREDS of thousands, even millions, of years, they were hidden. No plants shared their tomb. No other animals. They lay beside each other inside the abyss, in a cave system named Rising Star, in a chamber called Dinaledi.
But there was no access to the skies or the universe inside the pitch-black cave, a cave so remote it would take a 45-minute crawl through the Dragon’s Back to reach a crack 12m long and 17.5cm wide into a chamber.
Inside the chamber lay one of the greatest discoveries in the history of science – a palaeontological treasure trove.
For Lee Berger, research professor in Human Evolution and the Public Understanding of Science at the University of the Witwatersrand, it started with a photo.
It was September 2013. Rick Hunter and Steve Tucker, two amateur cavers, were exploring the Rising Star cave system. It lies near Sterkfontein and Swartkrans and is one of the most explored valleys in Africa. Rising Star has been known for almost 50 years. It has been mapped, people thought completely. Almost every palaeontologist in this country has searched for fossils in this valley. But they missed the biggest find. The cavers went into the pitch black and found the Dinaledi Chamber. They saw bones lying on the floor. A week later, they took a picture.
On a laptop, Berger saw a picture he thought he’d never see as a scientist. “I saw a mandible, the mandible of a primitive hominin, lying on the floor of this chamber. That shouldn’t be. We find our fossils in hard dense rock,” Berger said.
“I thought for certain what I was looking at was a skeleton. Possibly the skeleton of an early hominin. That alone is unprecedented. You shouldn’t see that sort of thing,” he said.
Berger knew immediately something extraordinary lay in that deep, dark, inaccessible cave, but he couldn’t fit into the 17.5cm gap. He needed scientists who could. So Berger sent out a plea on Facebook.
He asked for skinny scientists. They also needed to be willing to drop everything and come to South Africa for a month. On November 10, a team of 60 scientists went to the cave, and six went in. Within hours, the first material came up. “By the second morning, we knew I’d been wrong about everything. It wasn’t a single skeleton; it was multiple skeletons,” Berger said.
At the end of the 21-day expedition, the team had recovered the largest percentage of individual hominin specimens discovered in Africa. The 1 550 bones came from at least 15 individuals. Every generation is represented. The floor of the chamber is covered by the bones of what the scientists now know is a new species of human relative. It is a hominin, a type of prehistoric creature that is part of the early human family tree. But it is not a human, Berger explains. If you were standing next to this species, you would not mistake it for a human being.
The scientists called them Homo naledi, “The Star”, in honour of the cave system they were found in.
But the true mystery of Homo naledi isn’t just in the bones they left behind. It lies in where they were found – that dark abyss. Where nothing else has lived – or died. How did Homo naledi get there? No animal can go into such darkness and survive.
“We have studied this chamber,” said Berger. “We’ve eliminated the normal causes of the accumulation of fossils like this.”
They’ve been in a deep remote cave never opened directly to the surface of the earth. All the sediment inside the Dinaledi Chamber comes from within the chamber. Homo naledi was well and truly alone.
The scientists have one conclusion: Homo naledi was brought into the cave by relatives, deliberately placed there – they buried their dead – an action thought to be the sole preserve of humanity.
What isn’t known is how they got in – did they climb in with their curved fingers? They must have used fire. But the living naledi went into the dark zone, at considerable risk to themselves, to put their dead there.
Berger said there was also good evidence that the bodies were placed there over time. The way they lay, all alone, has also created another mystery. We have no way of knowing how old Homo naledi is. There is no rock overlying them, no rock under them. There is no datable sediment around them.
“It is an extraordinary circumstance,” said anthropology professor John Hawks, one of the excavation’s lead researchers.
“Naledi seems to be a type of time traveller. We can tell from their physical features that they must sit at the base of our lineage. They are so primitive in many ways.”
Berger said if our present understanding of the origins of our genus was correct, Homo naledi must originate from a time prior to 2.5 million years ago.
Homo naledi also could have continued down through time and be hundreds of thousands of years old. Nobody knows. “They may go back into deep time. Whatever it is, we are about to have a lot of fun. We have enough fossils and evidence to take us on a very long journey,” said Berger.