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.
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.
Once the 1,350 fossils and fossil fragments were recovered from the caves, they were stored, curated, and accessioned at the University of Witwatersrand. It was clear, however, that thousands of bones remained at the site and that Rising Star would very quickly become a long-term research project, not the salvage operation that the team had started out thinking it was.
Before more fossils were excavated, however, the recovered ones needed to be prepared and analyzed, which takes time and effort. Traditionally, analyses of fossil hominin material—especially fossils that have the potential to be new species—are undertaken by senior scientists, and there can be considerable lag between the discovery of material and the formal publication. Moreover, historically, journals have not always required that fossils’ data be part of their publication.
Berger and Hawks wanted something different. There were so many fossils to analyze, they concluded, that the project needed a massive workshop with scientists working in collaboration. They wanted, as they stated in their workshop advertisement on Facebook, “early career scientists” that would “be willing to share these data and skills” in a “collaborative workshop.” And they wanted the fossils to enter the published record in a timely way.
“I think that there is a generational shift right now that’s turning paleoanthropology into science,” Lee Berger explained to me. “We’re putting data out there and encouraging open collaboration.”
They had more than 150 applicants, and in May 2014, more than 40 came to Johannesburg to work through the cave’s fossil materials for five weeks. Several workshop participants estimate that well over 10,000 person-hours went into analyzing the fossil assemblage. “The workshop was larger than is typical,” biological anthropologist Caroline VanSickle offered over email. “It’s rare for that many paleoanthropologists to be in the same place at the same time for that many weeks. The number of participants was dictated, in part, by the magnitude of the fossil find.”
At the workshop, scientists analyzed the different skeletal elements and analyzed the wear patterns on the bones. During the live-tweeted excavations, questions poured in asking the team what fossil hominin species were in the cave and how the bones got there. The workshop was the opportunity to begin to work through those questions and more. “I think we did a remarkable job of pushing knowledge boundaries, encouraging other scientists to refine an understanding of naledi, and sharing our work with the world,” biological anthropologist Zach Throckmorton said.
The results were published in the open-access peer-reviewed scientific journal eLife on September 10, 2015. The group’s move to publish such an important, exceptional celebrity set of fossils in an open-access journal—instead of the more traditional journals like Nature and Science—sent a clear message. Although traditional journals carry a certain cachet and gravitas in scientific circles, they live behind paywalls and are slower to turn around peer review than their open-access counterparts.
“With Rising Star’s thoughtful and deliberate collaboration over the years, we’ve shown that you don’t have to pit speed of publication against quality,” John Hawks explained to me. “You can have good work that’s done relatively quickly by paleo standards. We want to bring in collaborators. We want to raise the level of science that can be done with these fossils.”
In their publication, the 47 authors argued that the fossils were a “previously-unknown species of extinct hominin,” with anatomy that most closely resembled other early Homo species, like Homo erectus or Homo habilis. (Although there were plenty of unique characteristics that set this new species apart.) The team named the species Homo naledi, noting that the 15 individuals recovered from the cave was the “largest assemblage of a single species of hominins yet discovered in Africa.” To date, the paper has been viewed more than 231,000 times.
Like most fossil hominins, the species was a mix of apelike and humanlike anatomical traits. But this particular new species came with more than its fair share of quirky, puzzling characteristics, making it difficult for scientists to figure out just where it ought to go in the hominin family tree. “These specimens are uniform in their diminutive size, particularly in relation to the contemporary Southern African fossil record, but they also possess a number of features that are comparable to recent humans,” biological anthropologist Adam Van Arsdale, who is not affiliated with the project, has noted. “Homo naledi offers us a chance to study the mosaic patterns of evolution,” he expanded in an interview.
For much of paleoanthropology’s history, being able to work at fossil sites or to have access to fossils themselves comes through professional networking. The Rising Star workshop—and collaborations that have spun out of that original workshop in subsequent years—have offered the opportunity for early career scientists to build new professional networks. These networks have grown in subsequent years.
As the original workshop participants have advanced their careers, they’ve actively worked to still involve junior faculty and postdocs, as well as graduate and undergraduate students, thus continuing to strengthen the networks of trust and reinforce the benefits of open collaboration. All are interested and committed to open access with fossils and data—with the Homo naledi material, of course, but also in other projects they’ve become involved in.
There are a lot of types of data that surround Homo naledi—everything from caliper measurements, to scans of the fossils, to 3D reconstructions of the Rising Star Cave, itself. The team works to maintain a balance of ensuring readily available data from the project with expert quality control. It’s not a free-for-all. “We can’t always be as open as we would like,” the postdoctoral researcher Ashley Kruger of the University of Witwatersrand made clear. Kruger is responsible for digitizing many aspects of the project. “It can depend on an institution’s rules. But we want data used in publications to be open and available.”
Open access isn’t free, as many champions as well as critics of Rising Star’s approach to data accessibility point out. The question of where data is stored, how it can be accessed, and who can use it depends on the scientists that generate it. But the success of open access also depends on the institutions and grants that fund research and whether journals require data openness and transparency with the publication of peer-reviewed research.
“The success of Rising Star’s policy of open access means that it will be harder for paleoanthropologists in the future to not be more open with their data,” Throckmorton said. “They might not be open to the same level as the naledi project, but they will be more open. There’s been a shift in expectations about publishing fossils.”
Rising Star’s push for open access didn’t end with the eLife publication. Traditionally, copies of fossils have been shared in the scientific and college communities through physical casts. Alternatives do exist, however—MorphoSource is an online archive that allows researchers to store and share 3D scans of fossils, for instance. The site is hosted by Duke University and allows registered users to download scans, free of charge, to print. “Fossil casts are expensive,” VanSickle points out, “sometimes difficult or impossible to obtain. Publishing the fossils in MorphoSource makes them readily available.” To date, scans of one hundred and forty-three of the Homo naledi’s fossils have been uploaded to MorphoSource.org where they are free to be downloaded and printed by anyone.
Rising Star has set up Google hangout sessions to chat with K-12 classrooms across the world. The project has also strongly committed to education through museum exhibits, classes, and outreach from Maropeng Visitor Centre in the Cradle of Humankind to the Perot Museum of Science and Nature in Dallas. This fall, on October 23, the project launched a free virtual reality app that allows “visitors” into the Dinaledi Chamber via their smartphone.
South African and current master’s student Nompumelelo Hlophe, who worked at the site during the short field seasons between 2015-2016, has translated the audio part of the Dinaledi tour into Zulu. “I love public outreach and explaining about Homo naledi,” Hlophe told me. “Telling them I was part of this project is really powerful. It’s changed my career goals.”
Rising Star today
The Rising Star project is far from over and is currently in a field season in the Dinaledi chamber through November of this year. “Rising Star feels like exploration in the true sense of the word,” Elliott told Ars. “It’s curiosity with a purpose.”
Purpose—in the form of hypothesis testing—has shaped the several short post-2013 field seasons in the Rising Star system. In addition to the excavations in the Dinaledi chamber, excavations began in a second part of the cave system, the Lesedi chamber, where three more Homo naledi individuals were recovered. Three more Homo naledi individuals were excavated from the Hill Antechamber, part of Dinaledi proper, bringing the most current Rising Star fossil tally to 21 Homo naledi individuals and more than 2,000 fossil fragments. Geologists have been through the caves to help piece together exactly how the system formed. The new team of excavators is being trained under the expertise and tutelage of Marina Elliott and Becca Peixotto.
As Rising Star has expanded in scope, the project now includes a full-time caving team—composed of Maropeng Ramalepa, Dirk van Rooyen, Mathabela Tsikoane, Steven Tucker, and Rick Hunter—to assist with excavation safety, help maneuver awkward fossils out of the cave, as well as to continue mapping the cave system. “I had always explored caves primarily to find new parts of cave systems,” Tucker explained. “After naledi, my eyes were opened to the possibilities of fossil discoveries in well-known caves.”
Some of the biggest current research goals for the Rising Star project focus on the question of why there are so many hominins—and only hominins!—in the cave’s chambers. Researchers have proposed that this pattern of fossils could only result from Homo naledi deliberately disposing of their dead; current fieldwork will continue to test this explanation by extending excavations in the Dinaledi chamber and including new test pits.
Fossil enthusiasts can follow the excavations from late October through mid-November on Twitter via #RisingStarExpedition and #DinalediChamber.
For most of its history, paleoanthropology has been a science built out of superlatives. Headlines tell us about the oldest fossil. The most complete skeleton. The earliest modern human. These sorts of claims make it easy to assume that the science of human evolution is driven by discovery, and the superlative-laden Rising Star project is proof that there’s a never-ending interest in fossil hominin finds.
But science is a social process, and, more than anything else, Rising Star has dared its fellow paleoanthropologists to re-examine how they’re going about the business of doing their science. Homo naledi has had enough cultural cachet to challenge the science of human evolution to be more open and accessible with its data.