Unknown Cave Of Bones: What secrets about Homo naledi were uncovered?

Daisy Phillipson
Paleoanthropologist Lee Berger in the Rising Star Caves

Here’s everything you need to know about the fascinating new Netflix documentary Unknown: Cave of Bones, and what secrets were uncovered about our extinct ancestors, the Homo naledi.

When we think of Netflix’s documentary category, true crime often springs to mind, with the likes of Making a Murderer going on to spawn a diverse range of films and series, a few recent examples being The Playing Card Killer, Victim/Suspect, and Missing: Dead or Alive?

But just as fleshed out is its collection of scientific and informative documentaries, from Fantastic Fungi to Chimp Empire, offering a fascinating insight into an aspect or viewpoint of the world and our history that we haven’t experienced before. 

Unknown: Cave of Bones is the latest entry, looking at the discoveries about our ancestors known as the Homo naledi, while adding a new and compelling piece to the mosaic that is human evolution. With the documentary now available for streaming on Netflix, we’ve broken down the secrets it uncovers. 

What happens in Unknown: Cave of Bones?

Unknown: Cave of Bones on Netflix takes viewers to South Africa’s Cradle of Humankind, a paleoanthropological site located about 50 km northwest of Johannesburg. Paleoanthropologist Lee Berger and his team of scientists have made an incredible discovery: the world’s oldest graveyard – and it’s not human. 

As per the official synopsis: “If Lee and his team can prove that this ancient, small brained, ape-like creature practiced complex burial rituals – it will change everything we know about hominid evolution and the origins of belief.”

The fossils uncovered by Lee and his team were of the Homo naledi, a hominin species who display characteristics similar to those seen in humans today – but with distinctly smaller brain sizes. They were alive at a time and place when, up until recently, we thought only humans were present, approximately 236,000 to 335,000 years ago. 

What makes the documentary so fascinating, however, is the examination of the evidence to suggest the Homo naledi displayed distinctly human behavior by burying their dead. The remains were first discovered in the Rising Star Cave system back in 2013, though the group’s continuous research has led to ongoing revelations, some as recent as this year. 

While the data is published in scientific journals and in the media, Unknown: Cave of Bones gives us a visual and surprisingly emotional perspective, showing scientists as they squeeze themselves into impossibly small spaces to get to the site, artist interpretations of how the Homo naledi likely looked and interacted, and a map of the complex cave system our ancestors would have had to work through to carry out the burying ritual. 

The Rising Star Cave and the Dinaledi Chamber

Speaking of impossibly small spaces, the Homo naledi fossils and suspected burial sites were discovered in the Dinaledi Chamber, a portion of The Rising Star Cave system that is incredibly difficult to reach. 

You can see a diagram of the cave system below: 

Image of the Rising Star Cave system

With no other access points, the documentary demonstrates just how hard our ancestors would have had to work to get to this site. In the first part of the film, lead excavator Dr Keneiloe Molopyane explains that they will be going to the first main section, named the Dragon’s Back Chamber. To get there, they have to squeeze through the Superman’s Crawl, a narrow passageway which gets its namesake from the fact that people can only fit by holding one arm tightly against the body and extending the other above the head. 

But this is nothing compared to the route to the Dinaledi Chamber, which involves climbing down a chimney-like chute, which is about 18 centimeters in width and goes down 12 meters. As new members decide to brave the expedition, the camera cuts to their perspective, showing a claustrophobic tunnel of jagged rocks, with nothing but darkness at the other end. 

Image of the small chute in the Rising Star Cave system

It’s at this moment we really get to understand how arduous the journey would have been for the Homo naledi, who had no tools, no safety gear, no lights – just themselves, the bodies of their counterparts, and fire to guide them through. 

What is Homo naledi?

Named Homo naledi by scientists in 2015, this extinct species of hominin is believed to have been alive approximately 236,000 to 335,000 years ago in South Africa. 

Some of their physical features, such as the shape of the feet and aspects of the skull, are strikingly similar to those found in modern humans, Homo sapiens. Yet, they also possess characteristics more common in much earlier hominid ancestors, such as the small braincase size and the structure of the shoulders and torso.

As per Tudum: “The creature was five feet tall and about 100 pounds, but with brains that were roughly one-third the size of ours. Despite their comparatively smaller brains, Homo naledi seemed to practice sophisticated burial techniques, something long considered to be unique to humans.”

Artist's interpretation of the Homo naledi

The way the Homo naledi remains were found, deep within the nearly inaccessible cave chamber, suggests these early humans may have deliberately disposed of their dead. If this interpretation is correct, Homo naledi may be the earliest species known to have practiced such behavior, indicating a level of social sophistication and possibly symbolic thought, characteristics previously associated only with modern humans.

This blend of traits implies that our evolutionary path was not linear, but rather a complex web of various species evolving concurrently.

What is the tool-shaped rock? 

Another jaw-dropping revelation in Unknown: Cave of Bones is that of a tool-shaped rock in what is believed to be a burial site of a child Homo naledi – upon further inspection, Lee suggests that it indicates the tool had purposely been buried with the child. 

Initially, the team wrapped up the skeleton fossils and its surrounding earth in plaster to preserve its positioning, before taking it in for a low-res x-ray scan. Upon seeing the images, they noticed a rock alongside the bones, although they initially presumed it was roof-fall from the caves above. “But this rock didn’t look like just any rock,” explains Lee. “It looked like a tool. And even more remarkable, it’s sitting right in the hand.”

Paleoanthropologist Lee Berger looking at the tool-shaped rock

With this idea in mind, Lee takes the artifact to the European Synchrotron Radiation Facility to make use of its advanced x-ray technology, resulting in the highest possible quality of 3D imagery of the rock. And what they discover are a series of features on the fossil including its shape and sharp edge, indicating it was likely a tool. 

Primatologist Agustin Fuentes goes on to ask: “If you place objects of importance with the dead, what does that say? That’s that next level of mortuary behavior… if it matters enough to risk your life and do all sorts of things to take your dead and to place them in particular places, and to give them tools that you use, you obviously think something about life and death.”

The Homo family tree

The Homo family tree refers to the various species within the genus Homo, which includes modern humans, aka Homo sapiens, and our closest extinct relatives. But the hominin lineage can be difficult to define as we are making new discoveries every day and our findings and fossil determinations are incomplete. 

But for a rough guide comprising what we know so far, the Smithsonian Institution has put together a diagram of the early human species accepted by most scientists, which you can check out below: 

The Homo family tree by the Smithsonian

Unknown is a four-part documentary series, with The Lost Pyramid, Killer Robots, and Cave of Bones available to stream on Netflix now, while Cosmic Time Machine drops on July 24. You can check out our other Netflix hubs below: 

The Night Agent Season 2 | The Gentlemen | Sex Education Season 4 | Beef Season 2 | Monster Season 2 | Will there be Ginny and Georgia Season 3? | All the Light We Cannot See | Stranger Things Season 5 | Chicken Run 2 | Heartstopper Season 2 | Florida Man Season 2 | Obsession Season 2 | The Sandman Season 2 | Glamorous cast and characters