Sunday, 21 December 2014

Bone bonanza: Chamber of secrets yields human remains

 28 November 2014 by Catherine Brahic - New Scientist - Issue No.1997

How 12 early humans ended up deep inside a South African cave is a mystery. Getting them out of it certainly wasn't easy

ALIA GURTOV was still in bed when she saw the job advert in her Facebook feed. "The catch is this," it read, "the person must be skinny and preferably small. They must not be claustrophobic, they must be fit, they should have some caving experience, climbing experience would be a bonus." She applied within an hour.

Gurtov wasn't the only one drawn to the post. Within minutes, it was being liked, re-liked, shared and blogged around the world. Elen Feuerriegel saw it on Tumblr. Marina Elliott received a link by email.
"OH. MY. GOD," wrote one blogger. "LOOK AT WHAT LEE BERGER JUST POSTED TWO MINUTES AGO GUYS." "What did they fiiiiiiiiiind?" wondered a commenter.

At this stage, Berger himself had little idea. The South African fossil hunter famed for his discoveries of early hominids was going on a few photographs. The pictures had been taken a few days earlier by two young cavers, deep inside the Rising Star cave system, 30 kilometres north-west of Johannesburg and 30 metres below ground. The cave is in an area dubbed the Cradle of Humankind because so many hominid fossils have been found there. The last big find was made by Berger in 2008: at nearby Malapa, he discovered two partial skeletons of a previously unknown species with a strange mix of apelike and human features – the 2-million-year-old Australopithecus sediba.

Now he was on the brink of another major discovery. The photos showed a jaw that Berger instantly recognised as belonging to some kind of early human – and there were more bones around it. That was enough to make Berger suspect this could be a big find, but what's been unearthed in this small chamber in the caves has surpassed even his wildest expectations. Back then, though, the immediate question was how on earth to excavate the bones properly in such an inaccessible location.

Set beneath the undulating veld of northern South Africa, the Rising Star cave system has been a playground for cavers for nearly half a century. Thick bush conceals the large opening to the cave. On 13 September last year the two cavers, Steven Tucker and Rick Hunter, made their way down into the maze of dark passages. The pair were hoping to find tunnels that no human had ever set foot in before.


                                          The Rising Star Cave System was certainly not your average office.                                                                                                                                                                                                                        
Beneath the Dragon's Back
Having crept up a narrow ridge known as the Dragon's Back, with 15-metre drops on either side, Hunter and Tucker arrived in a chamber thought to be a dead end. They had been here before, but on this particular day they found something new. Right at the back of the room, the pair came across a crack in the floor. Peering down, they discovered a narrow chute that appeared to lead into another chamber. "To me that's really exciting," says Tucker, "because you have no idea what you're going to find down there."

At around 20 centimetres wide, the chute is so narrow that Tucker had to point his toes just to get in. Undaunted, he began the descent. Falling down Alice in Wonderland-style was not likely: Tucker's body was jammed up against the rock in every direction. Inch by inch he wriggled deeper.

Tucker's gamble on his small frame and years of experience paid off. Twelve metres down the chute, he emerged through the roof of another chamber and climbed down to the floor. The room was barely 3 metres wide. Flowstones and stalactites dripped from the ceiling and walls, and shimmered in the beam of his head-torch. Looking up, he judged that the ascent would be harder than the descent but – fortunately – not impossible. A narrow passage leading out of the jewelled chamber and on to another was just wide enough to pass through, so he called out for Hunter to join him.

The first thing Tucker remembers seeing when they shuffled through into the next chamber was yet another passageway leading out of it. The bones came second. They were sticking out of the cave floor. "The first thing you think is [the bones] aren't something small like a bat," he recalls. "So you wonder, 'If I struggled that much to get in here, how did these get in?' That was probably the thing that made us look at them properly."

Berger had been asking caving clubs to get their members to look out for fossils. So when Tucker and Hunter spotted a jawbone with what looked like human teeth, they snapped a few pictures before moving on. "We had no idea how important that discovery was," recalls Tucker. "I'm not sure how many fossils we saw that first time, but when you think of other fossils like Lucy – these didn't look as impressive."

Three days later, the pair were in Berger's office at the University of the Witwatersrand in Johannesburg. When he saw the pictures, his jaw dropped. "I immediately recognised that I was looking at a mandible, and that it was notHomo sapiens," Berger recalls. The jawbone alone would have been thrilling. We know so little about our ancestors that even a single bone can give up a host of secrets.

But it was the fact that there were more bones in the background that made Berger really excited. There might be at least part of a skeleton. "That meant getting those bones out was worth every effort," he says. "You've got to remember that we spend tremendous effort and good old-fashioned money trying to find just bits and pieces of these things. We might spend three months in the field and be very happy if we come back with a single mandible. That's how rare these objects are."

Before the week was out, Berger went to see the cave. He couldn't fit down the chute, so he sent his teenage son in with Hunter and Tucker. When Matthew saw the bones, his hands began to shake. It was minutes before he could steady them enough to take pictures. "Daddy," he said after shimmying back up, "it's beautiful."



Underground astronauts
Berger's Facebook appeal for particularly petite potential palaeoanthropologists went online just days later. "Dear Colleagues," it began, "we need perhaps three or four individuals with excellent excavation skills for a short term project that may kick off as early as November 1st 2013." It was 6 October.

A year on from Berger's post, the excitement is still fresh among the six women he recruited – including graduate students Gurtov, of the University of Wisconsin-Madison, and Feuerriegel, of the Australian National University in Canberra. Berger affectionately refers to them as "underground astronauts". In separate emails and conversations, with moments of intoxicated laughter and genuine passion, they all convey incredulous wonder at what happened in such a short period of time. People were interviewed over Skype, and invited to pack their bags and hop on planes. They flew in from around the world, still mostly clueless about the adventure ahead, thinking simply that it would be fun.

Barely eight weeks after Tucker and Hunter had shimmied down the chute, the expedition was on the ground. They set up camp during the first week of November. In a matter of days, 20 tents went up. Generators powered a collection of computers, lights and cameras, linked to the inner sanctum by a mess of cables. The plan was for the six recruits to retrieve as many bones as they could find, assisted by experienced cavers including Tucker and Hunter. Above ground, a team of somewhat larger senior palaeoanthropologists could watch and supervise everything that was happening beneath their feet, in real time.




                   Slimness was an essential requirement for retrieving the bones.                                                                                                                                                                                                                                     
Marina Elliott, a PhD student from Simon Fraser University in Burnaby, Canada, was first into the chute. "From the top looking down, the rock looks like a narrow tunnel full of shark's teeth coming out at odd angles," she recalls. "Like you're descending into a jaw. It was kind of terrifying." At its narrowest, the chute pinches down to 18 centimetres, so narrow that Elliott had to turn her head to the side to get through.

She compares entering the inner chamber to accounts of Howard Carter opening Tutankhamun's tomb. "Someone behind him said 'What do you see?' And Carter whispered, 'Things, wondrous things'... It was breathtaking. Everywhere you turned, your headlamp fell on fossil material... the more you looked the more you found. And it just got crazier from there. Every day was one of those days where you just think, 'My god, is this real?'"

The six worked in shifts of four or five hours, picking the bones clean with toothpicks before carefully packing them into bubble wrap and Tupperware to begin the long ascent. It quickly became clear that the entire floor of the chamber was underlaid with bones, so they padded around barefoot to cause minimal damage. Lifting each fragment was like a delicate game of pick-up-sticks, says Becca Peixotto, a PhD student in anthropology at the American University in Washington DC. "The longer you looked, the more bones you saw. To the point that we'd think we had cleared a whole area, and then we'd sit there for a few minutes and see more fossils."

She recalls having to lift the first piece of bone out of the ground – it was the jaw spotted by the cavers – aware that it had not been moved for thousands of years, and that some of the world's biggest experts on prehumans were watching her every move over CCTV.

For Berger, finally seeing the bone for himself was a huge relief. Until that moment, he had not known for sure that the find justified a major expedition involving 60 people from around the world. That day, 10 November, made it all worth it: the jaw was indeed from a hominid.

The next day blew everyone's expectations away. A femur came up, and then another – and they were both right femurs. In the science tent, heads were shaking in disbelief. There was more than one individual down there. "This just doesn't happen," said Berger. Thousands of hominid fossils have been found but most consist of one or two bones, or the odd tooth. Finding more complete skeletons is extremely rare. Finding several skeletons is rarer still.

And there was more to come. Much more. Before long, the six women were sending a regular stream of Tupperware boxes up to the surface. Hundreds of fossils were carried out of the cave. The senior scientists had expected to have enough time between finds to start analysing the bones, but they could barely log them fast enough.

They ran out of boxes. Someone was sent to buy more. They ran out again. The project bought out the stock of every shop and warehouse that sold Tupperware in the area. The nearby site of Sterkfontein has produced only about 500 hominid fossils after 65 years of excavation. In three weeks, the Rising Star team removed 1200 fossils. Based on the teeth they found, says team member John Hawks of the University of Wisconsin-Madison, there are more than 12 individuals.

It is a mystery how the bones ended up where they did. Tucker, who has explored the passages beyond the bone chamber, doesn't think there is another way in. He also thinks they have ruled out an accidental fall. Nor is there any sign that the individuals fell victim to predators who carried them in – there are no bite marks, and in any case, how would the predators get in? "I don't think anyone has any real idea of how they got there," says Tucker.

Bringing up the first piece of skull was one of the more memorable events during those extraordinary days. Wrapped in pink bubble wrap, nestled inside a cereal bowl and packed into Tupperware, it was passed from hand to hand up a human chain. Hunter lodged himself inside the chute and passed it from Elliott below to another caver above. All the way down the Dragon's Back, the team passed the precious parcel in near silence.

"I think for a lot of people, it was very emotional," says Elliott. "It's extraordinary to think of this animal, that this is an ancestor to all of us." Whether it is a direct ancestor or more distant branch of the human family remains unclear. Beyond the fact that they are definitely early hominids, the team will not say exactly what they have found ahead of the formal publication of their findings.


                          CCTV helped the team above ground guide the momentus work under way below.                                                                                                                                                                                                       
Bone bonanza
In the past, hominid fossils have often been hoarded by the researchers who found them. " Ardi", discovered in Ethiopa in 1994, was only unveiled in 2009, for instance. But we won't have to wait that long this time, as Berger's team is doing things very differently. Around 50 anthropologists were invited to a workshop in South Africa earlier this year. They were given free access to all the fossils – 1500 in total, including 300 unearthed by a second expedition in March – and invited to analyse the heck out of them. Their findings will be announced early next year.

And all the signs point to it being a big announcement. The sheer quantity of fossils is incredible, says team member Steven Churchill of Duke University in Durham, North Carolina. And it's nowhere near over. Not only are there still bones in the original chamber, but in November 2013 Hunter and Tucker found more in a different part of the cave.

"At the end of the day," says Churchill, "we will know these hominins very well, and we will likely be able to say much about their biology and their place in the human evolutionary story."


"This article originally appeared in New Scientist, 28 November 2014. Reprinted with kind permission of New Scientist."
 
Catherine Brahic
is a reporter for New Scientist

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