On September 10, 2015, scientists formally announced that a new species of hominin had been discovered in the Rising Star cave system in northern South Africa. But the discovery was far from a secret—the team had live-tweeted their field season earlier. They named the species Homo naledi—for “star” in the local Sotho-Tswana languages.

To date, what scientists know about Homo naledi comes from more than 2,000 fossil fragments that make up 21 individuals—spanning male and female adults as well as infants—from three different parts of the Rising Star’s cave system. The species is estimated to be between 236,000 and 335,000 years old, based on several dating methods. For a science that can count the bones of some entire fossil hominin species with the fingers of one hand, finding so many fossils of one species in one place is unprecedented.

With Homo naledi’s new-found celebrity within paleoanthropology, project leaders and paleoanthropologists Lee Berger and John Hawks were savvy enough to parlay the situation into an opportunity to challenge the industry’s status quo. The National Geographic-backed Rising Star project pushed a new set of social mores and practices around data openness that enabled researchers to work through the Homo naledi material in an efficient, timely, and professional manner. And in retrospect, a lot of factors made Rising Star well situated to prompt a shift toward more open-access practices across paleoanthropology.

“We have an open invitation for colleagues to check our work,” Lee Berger explained to Ars. “And they can do this since we’ve made open collaboration such a key part of Rising Star.” He paused for a minute and continued. “I think we’re broadening what science, for paleoanthropology, means because people can see the site and fossils for themselves to test their conclusions. The data are available.”

The Cradle of Humankind

The story of Homo naledi actually begins millions of years before the Rising Star expedition ever set up camp some 25 miles outside of Johannesburg in South Africa’s Gauteng province.

Caves in that area of South Africa form as water percolates through the cracks and fissures of the region’s dolomite rock and slowly erodes the rock away, forming underground caverns of all shapes and sizes. As water flows through these caves, it leaves behind deposits of calcium carbonates—easily recognizable as concrete-hard breccias or sheet-like deposits of flowstone found along cave walls. In the Rising Star cave system, this resulted in a network of chambers, including those where researchers have recovered Homo naledi fossils.

For scientists piecing together the story of South Africa’s ancient environments and evolution, these caves act as time capsules. Over eons, plant and animal remains (not to mention hominins) have been found in the caves. Enough hominin bones were found that in 1999, that region in northern South Africa—and all of its fossil-filled caves—was designated as a 180-square-mile UNESCO World Heritage site called the Cradle of Humankind, dedicated to humanity’s paleoanthropological history.

These bones got into the cave through a number of routes. Rodents, for example, drag bones into the caves and have for millennia. Water from underground sources can move bones from where an animal died to somewhere else in the cave system entirely. Although these caves are incredible sources for finding fossils, understanding how those fossils appear in their present locations—to be discovered and excavated by modern scientists—is anything but straightforward.

Visions of America/UIG via Getty Images

Visions of America/UIG via Getty Images

Visions of America/UIG via Getty Images

From caves to Facebook and Twitter

In August 2013, Professor Lee Berger of the University of Witwatersrand hired Pedro Boshoff to survey caves in the Cradle of Humankind, mapping which had fossil deposits. Boshoff, a caving specialist, expanded his team to include Rick Hunter and Steven Tucker. Cavers had been in the Rising Star system since the 1970s, and, armed with a map from 1985 as a guide, Tucker and Hunter began systematically exploring.

“I started out in the Rising Star cave system in 2011 as a member of the Speleological Exploration Club,” Steven Tucker explained over email. “It has always been one of my favorite caves, looking for new and explored areas. By mid-2013, I had spent well over a hundred hours in there.”

Tucker and Hunter found that they could wriggle through a rather daunting, unmapped 18-centimeter slot in the cave, so squirm through they did. Once through the slot and after negotiating their way down a chute, Tucker and Hunter were in a final chamber that had an inordinate number of fossils. (“When we first saw the mandible, we thought, maybe this was the last guy who came down to the chamber and didn’t make it out,” Hunter joked during an interview.) When they showed Berger photos of the fossils, his interest was piqued, to say the least.

From the photos, Berger could see that there was fresh damage to the bones, likely from other cavers who were unaware of what they were treading upon. After consulting with colleagues, Berger decided that it was prudent—necessary—to excavate the fossils, properly map their contexts, and to do it quickly to avoid any further damage. Getting proper permits in place and with the backing of National Geographic, Berger began to assemble a team that would have the requisite scientific and caving background necessary to pull off the work. He started by writing a job ad.

“Should I just mail this to my colleagues and ask them to distribute in the normal way?” Berger wrote in his 2016 bestseller about the expedition, Becoming Human. “I guessed there probably weren’t more than a handful of people in the whole world who fit the description and were available on such short notice.” Berger decided to post the notice on Facebook and, from there, it quickly tore through the Twitterverse. The underground team was six women with extensive archaeological and caving experience—Marina Elliott, K. Lindsay Hunter neé Eaves, Elen Feuerriegel, Alia Gurtov, Hannah Morris, and Becca Peixotto.

“It took me 45 minutes to get down to the Dinaledi Chamber the first time,” said Marina Elliot, a biological anthropologist at the University of Witwatersrand and the project’s current field director. “When I finally popped out of the chute and slid through the final hallway to the Dinaledi Chamber, I could see that the floor was littered with bits of bone, and the stalactites around me glittered from the light thrown around by my headlamp. It was mind-blowing.” Elliott paused for a moment and then laughed. “I expect it’s what Howard Carter’s team felt when they opened King Tut’s tomb.”

The November 2013 field season was set up to run like a salvage archaeology project. The point was to excavate in the Dinaledi Chamber (as the space was named)—to get in, get the fossils, document the context, and get out. When Marina Elliott and Becca Peixotto first reached the chamber, they started flagging fossils on the cave floor’s surface. Their count was over 300 fragments. “Well, we took off our shoes and socks, to make sure we wouldn’t damage anything,” Elliott clarified. “The fossils were—are—incredibly fragile.”

“We use toothpicks to excavate,” Peixotto explained. “We move one grain of sediment at a time, looking at everything.” The team of archaeologists also use paintbrushes and Tupperware containers to excavate and transport fossils to the surface—a curious juxtaposition of gear from the Dollar Store with the sophisticated technology of cameras, cables, and Internet. The latter was there to allow the above-ground support team in the “command center” to watch the excavations via a live feed, carefully documenting the fossils’ recovery. “We also use porcupine quills, which are perfect for the sediments,” Elliott offered with cheerful aplomb. “And sometimes we just have to wait for porcupines to leave the caves before we can go in.”

As the team excavated, a curious pattern began to emerge. All of the fossils were hominin bones. In caves with fossil hominins, it’s not uncommon to find non-hominin bones, indicating that other animals used the caves at some point and died there, or that natural forces, like water, could have carried the bones to where they were discovered. But at Rising Star, there weren’t any fossils from any other species. It was unexpected enough that “at one point, Lee pulled me aside to ask if we were only excavating the hominin material and skipping over other stuff for later,” Elliott recalled. “I assured him that we were excavating everything. There just wasn’t anything else besides the hominins.”

Over the course of the first field season, all of the excavators—underground astronauts, a term the media seized on—took turns on shift. Because it was so arduous to shimmey into the Dinaledi Chamber, shifts lengthened from 1-2 hours to 3-4 hours, to maximize the output from the time spent just getting to the fossils. The fossils were mapped and bagged. Sediment was collected to be screened later in the lab. The entire season lasted three weeks, and science Twitter was captivated throughout, following along with updates from #RisingStar.

Popular press tracking big fossil discoveries is nothing new. When the famous fossil Lucy was discovered in the Afar region of Ethiopia in November of 1974, her discoverer, Donald Johanson, held a press conference in Addis Ababa on December 21 to introduce Lucy to the media, well before the fossil was published in academic literature. Many fossil discoveries come with the opportunity to engage the general public. Before Rising Star, however, no fossil hominin excavation had been so instantly shared across the world.

Listing image by Photo by Robert Clark/National Geographic; Source: Lee Berger