Elen Feuerriegel risked her life to recover bones hidden in a cave below the rolling hills of South Africa. What she found helped open a new chapter in the story of human evolution.

Share Elen Fuerriegel was nicknamed an underground astronaut when she explored the dark, dangerous frontier of the Dinaledi Cave

Share Lee Berger holds the skull of Neo, a male Homo naledi fossil

Share Elen Feuerriegel in caving gear

Share The Rising Star expedition site north west of Johannesburg

Four years ago, Dr Elen Feuerriegel was trawling the internet when she saw an ad.

The ad was unusual — it asked for three or four people for a short-term project, but they had to be skinny, preferably small and could not be claustrophobic.

They also needed to be fit, have some caving experience, a good attitude and be a team player.

And they had to be willing to work in cramped quarters.

Elen was intrigued.

The ad described her to a tee.

"I sat on it for an hour or two, thinking 'well if I fit the bill I should really apply' but I didn't think I'd have a chance in heck that I'd even be considered," she says.

"And then I thought 'I would be a fool if I let this opportunity go by without trying.' It cost me nothing, so why not?"

So the 24-year-old Australian PhD student sent her resume — and her measurements — to a man she'd never met in South Africa.

An extraordinary discovery

Just days before posting the ad in early October 2013, Lee Berger had sent cavers down an unexplored site he'd spotted on Google Earth.

The cavers returned with extraordinary photos.

"I was looking at pictures of a fossil that looked to me like a skeleton just sitting there in the dirt on the floor of a cave 40 metres down, 170 metres into a system," Professor Berger says.

"No-one in history has seen something like that on the continent of Africa."

Share The Cradle of Humankind World Heritage Site is one of the richest fossil sites in the world

The photos were taken in the Rising Star Cave system near the Cradle of Humankind, just 50 kilometres north-west of Johannesburg.

The World Heritage site is dotted with rich fossil sites and ancient caves, many of which were mined for lime for use in the gold industry.

The Rising Star Cave is 800 metres away from the famous Swartkrans Cave, where remains of human ancestors up to 2 million years old have been found along with stone tools and evidence of fire use.

Although paleoanthropologists have been excavating in the region since the early 20th century, many rocky outcrops and caves have not been explored.

Professor Berger, a US-born palaeoanthropologist based at the University of Witwatersrand, has been mapping the area using Google Earth for a decade.

He made his first big find in 2008 — a 2.5 million year old ancient human called Australopithecus sediba.

But since then he'd found nothing — until that day in 2013 when he sent the cavers down into the Rising Star Cave system.

A big job ahead

As Professor Berger soon discovered, reaching the Dinaledi chamber — one of two chambers where fossils have been found — is a dark and dangerous journey.

Share Illustration of the Dineledi cave

To get to the bone chamber you have to squeeze through Superman's crawl, so-called because you have to wiggle through with one arm extended.

"If you get stuck someone grabs your arm and they drag you through to avoid breaking your ribs," he says.

Then you have to climb 20 metres up a jagged spine of rock called the Dragon's Back.

"If you fall off either side you die, quite literally," Professor Berger says.

Then, in front of you is a plunging 12 metre-deep, 18-centimetre-wide vertical fissure called The Chute.

Frustrated that he was too big to make it down this last descent, Professor Berger asked his 15-year-old son to descend The Chute. When Matthew returned with images of a jaw bone, Professor Berger knew he needed to put a team together. Fast.

"So I put a Facebook ad, it said basically I need skinny scientists and I'm not going to tell you what you are going to do, but you need to drop everything, I'm not going to pay you, but come to South Africa," he recalls.

"Remarkably I found six extraordinary scientists out of over 60 applicants that just happened to be women."

Share The Underground Astronauts: (L-R) Becca Peixotto, Alia Gurtov, Elen Feuerriegel, Marina Elliott, Lindsay (Eaves) Hunter, Hannah Morris

'A wonderful scientist'

Elen had heard of Professor Berger's work on Australopithecus sediba.

At the time, she was in her first year of a PhD studying human anatomy under Professor Colin Groves, a world renowned paleoanthropologist at the Australian National University.

She'd worked on Neanderthal dig sites in Spain, and had explored the Jenolan Caves in the Blue Mountains.

Share Elen Fuerriegel in bone room at Witswatersrand University

The moment Professor Berger met Elen via Skype he knew she was right for the job.

"Elen is a wonderful scientist," he says.

"She is this eccentric, but brilliant mind.

"She was doing her PhD in Australia, she had the right measure of risk taking versus safety, knowledge, and she had a great understanding of hominin morphology."

And, at only 160 centimetres tall, she was also the right size to squeeze through the tightest of the cracks in the cave.

"Basically all I did was to reassure Lee that I could fit through an 18-centimetre pinch," Elen says.

Share Expedition leaders Professor Lee Berger and Professor John Hawkes in front of the command centre tent.

Three weeks later, Elen arrived at the Rising Star excavation site — a bustling little city of green tents. One of these tents housed technology that would monitor the team's progress through the cave system, and beam their journey to the world via social media.

The women — nicknamed the 'underground astronauts' — began work.

Elen watched her colleagues, Marina Elliott, Becca Peixotto and Hannah Morris, decked out in hard hats and blue ovals, take the first descent.

"I remember watching on the CCTV we'd set up in the system up in the headquarters of the expedition ... and how I wished I was there with them experiencing it for the first time," she says.

The dangerous descent

Elen didn't have to wait long. The next day, she was in the second team.

"When you first descend into any cave, in particular the Cradle of Humankind, the first sensory experience you have is of the dark but the second is the dust," she says.

"The dust gets everywhere, it gets kicked up very easily when you move through the system so you tend to breathe it in and you can taste the dirt on your tongue."

Each day the teams spent three to five hours squeezed between rock faces with just the light from their headlamps to see where they were going. The muffled sounds of bats flying past in the humid air filled their ears.

"The feeling of claustrophobia is a little bit more intense when you can't see where you're going," she says.

Share Anthropologist Dr Marina Elliott was one of the first 'astronauts' to enter the cave

Share Elen Feueriegel deep in the Rising Star Cave system

Share Scientists monitor their colleagues excavating a cave

Even though the team's moves were captured on CCTV, they had limited ability to communicate with those working above ground. So they had to rely on each other.

"You don't ever want to leave anyone behind because sound doesn't travel all that well, so you need to be very aware of who is in your team and what they're doing at any given time," Elen says.

"We were pretty conscientious about checking with one another to make sure everyone was doing well getting through the system, particularly the most challenging parts."

The most challenging part was The Chute. The fissure was so narrow that Elen and her colleagues could not even wear safety harnesses.

"When you first go through the opening to the fissure you have to drop in feet first and there's not enough room that you can see where you're going," Elen says.

"You feel blindly around with your feet for any possible foothold you could before slowly wriggling your way very carefully down without looking at your feet."

The sides of the chute were filled with interlocking spurs of stone.

"They were handy sometimes but at other times they could catch your clothing, catch your jumpsuit and choke you," she says.

A chamber full of bones

But at the bottom of this chute was the most stunning thing Elen had ever seen.

"One of the most treasured experiences I have is walking into that chamber for the first time," she says.

"The ground was covered in white stuff," she says, pausing. "White stuff!"

"And it took me a second or two to realise that all the white stuff I was seeing on the ground was bone material. And it was everywhere."

Share The team recovered around 1,500 fragments from at least 15 individuals.



Over the next three weeks Elen and her colleagues ferried thousands of fragments of bone to the surface.

The precious cargo was carefully covered in bubblewrap and packed in Tupperware containers.

Then, just like a pass-the-parcel, it was wrapped in more plastic and placed in a dive bag.

"In some cases where we had very fragile elements, like the skull for instance, we sort of daisy chained it out of the system. We had people set up at strategic points through the system," she says.

Once they were above ground, the pieces were taken to the science tent, where they were unwrapped, photographed, cleaned and catalogued.

All up, the team recovered around 1,500 fragments from at least 15 ancient humans of all ages, including the almost complete skeleton of one individual.

Curiously, though, there were no signs of animal bones or tools with the human remains.

Introducing a star to the world

Share Homo naledi had a small skull and a brain the size of an orange.

Two years later, Professor Berger held a press conference to announce to the world that the team had discovered a new species of ancient human in the caves — Homo naledi.

Naledi, which means 'star' in the Sotho language, was a bizarre combination of ancient and almost modern features.

This new member of our family tree had a brain the size of an orange and a small flat face — much like the famous Lucy skeleton from East Africa. It had the shoulders of an ape, the spine of a Neanderthal, and long arms and legs that led to hands and feet that resemble our own species, Homo sapiens.

Share Homo naledi's feet were very similar to ours

At the time of the announcement the bones had yet to be dated, but features suggested the ancient human was around 2 million years.

The discovery opened a new chapter of human evolution — and a fiery debate about how science should be conducted in the age of mass media.

Some palaeoanthropologists felt the team, which was funded by National Geographic, had rushed the results and speculated on the findings.

For a start, the team was widely criticised for publishing the discovery before knowing the age of the bones.

Dating of the bones, released 18 months after the discovery was announced, showed the bones between 236,000 and 335,000 years old, which was much younger than thought.

The expedition, was also criticised for using junior scientists who were all women.

According to the younger generation of paleoanthropologists like Elen, the field is dominated by men with big personalities and big opinions. And, with more scientists than bones, it's highly competitive.

"We see these powerful personalities who limit research access to key fossils so they can ... keep control of the story that is being told about those finds," Elen says.

"I've had my experiences of sexism in this field, particularly getting critique for only getting a job because I'm a woman scientist."

But the field is becoming more egalitarian, she says.

"It's through these people who value the work of early career scientists, of giving opportunities to people who aren't typically chosen for these kinds of projects, that we're beginning to see a bit of a change," she says.

"In that sense I think we're making progress. It's still slow."

Return to Rising Star

Elen's connection to Homo naledi continues.

After finishing up the initial dig, she returned to Australia and completed her PhD, which included her research on Homo naledi.

Elen now works at the University of Washington in Seattle, where she teaches and studies the ancient human's upper limb remains.

But the thrill of finding bones no-one has ever touched is still in her blood.

Over the past four years she's been back to Rising Star for a couple of short digs.

Next month, she's returning to the caves again.

Share Dineledi cave entry.

The plan is to excavate the base of The Chute to the Dinaledi chamber to work out if this was the route the Naledi took to get into the chamber.

She'll also revisit a second chamber known as Lesedi, where the team found 131 fragments including the almost complete skull of an adult Homo naledi man — known as Neo.

"In this profession you deal with fossil material, but typically its fossil material that 100 people have handled before you," she says.

"It's kind of nice to know whose hands have held a fossil but it doesn't really compare to being able to unearth something yourself and think 'this is something completely new to science, this is something that hasn't been looked at before possibly in millions of years'.

"Your eyes are the first to fall on it in such a long, long time, and it's an incredible privilege to be able to do that."

Credits

Additional photos in panels: Getty Images, National Geographic, Elen Feuerriegel