In case you haven’t heard, there’s a new hominin in town. Announced on Thursday, September 10, this previously unknown species, within our own genus Homo, is unlike any ancestral human described before. And even though we don’t yet know where this tiny-brained species fits in our family tree, Homo naledi is already shaking up our understanding of our origins, and its unexpected behavior – deliberately and repeatedly disposing of its dead – has extraordinary implications on our view of what makes us, humans, unique.

Lucky enough to see H. naledi in the flesh (well, bone) IFLScience has already shared with you its remarkable features. But how did paleontologists come across this unprecedented discovery in the first place? That is also a story well worth sharing. So here is a snapshot of this incredible journey.

It all began back in September 2013, when two cavers Steven Tucker and Rick Hunter were clambering, squeezing and crawling through their idea of an underground playground: a formidable yet fascinating cave system known as Rising Star. Located within South Africa’s Cradle of Humankind, this World Heritage Site is utterly unique on the continent of Africa. One of the richest known fossil hominin sites in the world, the Cradle of Humankind has produced a series of important finds that are helping piece together our origins, like the iconic fossils Little Foot and Mrs Ples; two australopiths – some of our most ancient ancestors.

Despite being a treasure trove of fossils, Tucker and Hunter weren’t actually on the scout for hominins. “We were just trying to find anything interesting,” Tucker recalled to IFLScience outside the cave. “We like finding new cave passages. Caves are one of the few places on Earth where you can be the first person literally to see the site.”

During one fateful trip, Tucker wanted to show his buddy an intriguing area called the Dragon’s Back, but in order for Hunter to squeeze past and get his fill of stalactites, Tucker was forced to climb down a small crack in the floor. And it soon became apparent that this was not just a small crack: it didn’t seem to stop, going deeper and narrower for around 12 to 15 meters (40 to 50 feet). “Was it scary? Actually it wasn’t. I think the excitement was a lot more than the fear of what was down there,” said Tucker.

Tucker called out for Hunter to join, and one by one the pair inched their way down the chute, before taking a four-meter (13-foot) plunge into darkness, with no idea what awaited below their dangling feet. A chamber, since you asked nicely. But not just any chamber: a burial chamber. But that revelation comes later. At this stage, all the pair knew was that they stood inside a dark area, nigh impossible to reach, with bones scattered across the ground.

That was enough for Lee Berger, research leader and professor of human evolution at the University of Witwatersrand, to get giddy like a school girl and start planning an expedition. But the problem Berger faced was not that he had a shortfall of willing experts: The newly discovered site required very slight individuals if they were to have any hope of squeezing through one challenging, 17.5-centimeter (6.9-inch) gap. So Berger called out to social media, and landed himself six slender experts, all women, who were willing to risk their lives in the name of science.

The daring Rising Star expedition was split into two phases, the first – the largest – of which took place in November 2013, involving a team of around 60 people that all set up camp around the site. Of course, it would have been much easier to just sack off the perilous 200-meter (656-foot) clamber required and blow it open, but Berger rightly asserts that it would not have been the right thing to do. “The rock is 2.9 billion years old… We don’t have a right to destroy it.”

^{Lee Berger inside the Rising Star cave. Justine Alford for IFLScience}

Standing outside the cave gave me the shivers. Not only because Berger kept yelling that there was a “death drop” just to the side of the entrance, but because I knew what the site meant in terms of our history. Touching the soil our ancestors carried their dead across aroused goosebumps, so I can’t even begin to imagine the emotions felt by those involved in recovering the fossils.

And it was these feelings that overrode any fear response from Lindsay Hunter, one of the lucky "underground astronauts" involved. In fact, Hunter relayed to IFLScience how she was more worried about being flown all this way, from the U.S., to find that she did not in fact fit inside. That’s why Hunter, among others, had been prepping as all dedicated explorers do: crawling under her bed and contorting herself through wire hangers for reassurance.

But no amount of bedroom gymnastics could prepare the team for what it would be like. Hunter paints a vivid picture for us: “Once you’re faced with the chute, you can’t see where you’re going; all you can see is darkness. You can’t put your head down at all; your head is always above your feet. So it’s literally like going down Alice’s rabbit hole. You just drop through and hope you’re gonna be OK.”

The first expedition was 21 days long, kick-started with the anticipation of finding just one individual. But by the third day, the team knew they had more on their hands. “By the end of the week we had more individuals than ever before in the entire history of human origins,” said Berger.

More than 1,500 fossils, from at least 15 individuals, is what they ultimately ended up with. So the excavation area must have been huge, surely? “It was 80 centimeters by 80 centimeters, to be precise,” expedition member Marina Elliott told IFLScience. An area they nicknamed the “puzzle box” because the bones were on top of one another like in Jenga. And they didn’t even have to dig deep to make the extraordinary find – a maximum of 20 centimeters (7.8 inches). A sign that there is likely plenty more to be discovered. “We have excavated maybe one tenth of the floor space. If the rest of the chamber has that much material… This is decades of work.”

^{Marina Elliott draws for us the rough size of the excavation area. Justine Alford for IFLScience}

Indeed, it seems that H. naledi is not the last we will hear from Rising Star. “We just discovered this new species,” Berger teases IFLScience, “but I can guarantee you that these hills hide treasures that have yet to be discovered, and some maybe that we already have…” 

^{Members of the awesome Rising Star expedition team, sat in the Rising Star cave. Justine Alford for IFLScience}

^{Image in text (1): The entrance to the Rising Star cave. Justine Alford for IFLScience}

^{Image in text (2): Homo naledi hand. Justine Alford for IFLScience}