It has been much anticipated since Professor Lee Berger, research professor in the at Wits, and a team of researchers, cavers and explorers announced in November 2013 that they had discovered a significant fossil find in a cave known as Rising Star in the Cradle of Humankind, some 50 kilometers northwest of Johannesburg.
Biggest find in Africa
They launched the Rising Star Expedition and have since then discovered more than 1 550 numbered fossil elements, the discovery is the single largest fossil hominin find yet made on the continent of Africa.
The fossils, which have yet to be dated, lay in a chamber about 90 meters (some 100 yards) from the cave entrance, accessible only through a chute so narrow that a special team of very slender individuals was needed to retrieve them.
So far, the team has recovered parts of at least 15 individuals of the same species, a small fraction of the fossils believed to remain in the chamber. “With almost every bone in the body represented multiple times, H. naledi is already practically the best-known fossil member of our lineage,” Berger said.
Appearance of ritualised behaviour
Perhaps most remarkably, the context of the find has led the researchers to conclude that this primitive-looking hominin may have practiced a form of behaviour previously thought to be unique to humans. The fossils — which consist of infants, children, adults and elderly individuals — were found in a room deep underground that the team named the Dinaledi Chamber, or “Chamber of Stars”.
That room has “always been isolated from other chambers and never been open directly to the surface,” said Dr Paul Dirks of James Cook University in Queensland, Australia, lead author of the eLife paper on the context of the find. “What’s important for people to understand is that the remains were found practically alone in this remote chamber in the absence of any other major fossil animals.”
So remote was the space that out of more than 1,550 fossil elements recovered only about a dozen are not hominin, and these few pieces are isolated mouse and bird remains, meaning that the chamber attracted few accidental visitors. “Such a situation is unprecedented in the fossil hominin record,” Hawks said.
The team notes that the bones bear no marks of scavengers or carnivores or any other signs that non-hominin agents or natural processes, such as moving water, carried these individuals into the chamber.
“We explored every alternative scenario, including mass death, an unknown carnivore, water transport from another location, or accidental death in a death trap, among others,” said Berger.
“In examining every other option, we were left with intentional body disposal by H. naledi as the most plausible scenario.”
This suggests the possibility of a form of ritualised behaviour (or repeated behaviour) previously thought to be unique to humans. Read the full media release.
It is the single largest fossil hominin find yet made on the continent of Africa.
Wits University announced the discovery of a new species of human relative, and named it Homo naledi, on Thursday, 10 September 2015.
Most remarkable, besides shedding light on the origins and diversity of our genus, H. naledi also appears to have intentionally deposited bodies of its dead in a remote cave chamber, a behaviour previously thought limited to humans.
Professor Lee Berger and the Rising Star Expedition have discovered more than 1 550 numbered fossil elements – the single largest fossil hominin find yet made on the continent of Africa.
Wits University Vice-Chancellor Professor Adam Habib, South African Deputy President, Cyril Ramaphosa, and Professor Lee Berger.
Professor Lee Berger (left) and South African Deputy President Cyril Ramaphosa (right).
Professor Lee Berger engaging with the media during the launch.
Professor Lee Berger (centre) with South African Deputy President Cyril Ramaphosa (to his left) showing the #naledifossils to delegates.
The Homo naledi fossils on display.
Prehistoric Tarzan-like ancestor
- By Wits University
The two papers, titled: The foot of Homo naledi and The hand of Homo naledi, describe the structure and function of the H. naledi hand and foot.
The second set of papers related to the remarkable discovery of Homo naledi, a new species of human relative, show that Homo naledi had unique Tarzan-features – climbing trees as well as walking upright.
The two papers, titled: The foot of Homo naledi and The hand of Homo naledi, describe the structure and function of the H. naledi hand and foot.
Taken together, the findings indicate H. naledi may have been uniquely adapted for both tree climbing and walking as dominant forms of movement, while also being capable of precise manual manipulation.
These fossils were recently reported by Lee Berger and his team, who described the discovery of more than 1500 fossils as representing a new species of the genus Homo. It has been called Homo naledi, associated with a name for star in the Sesotho language.
But the age of Homo naledi is not yet known with certainty. The new species has not yet been dated. Unsuccessful attempts had been made by Paul Dirks and members of the Rising Star team to obtain an age. They used techniques applied previously to date a range of fossils. These included Australopithecus africanus, such as the famous “Mrs Ples” skull, as more than two million years old, and fossils of Paranthropus robustus and Homo erectus.
In a new paper in the South African Journal of Science I suggest that Homo naledi lived two million years ago (plus or minus 500,000 years). If shown to be correct, this will help to place Homo naledi in the family tree of human relatives.
The variance is based on the fact that the earliest date for Homo rudolfensis is about 2.5 million years, and the date for certain African Homo erectus samples is about 1.5 million years.
Although different, Homo naledi is most similar to fossils attributed to Homo habilis (about 1.8 million years old), and to a lesser extent to fossils of Homo rudolfensis and Homo erectus.
Taken together I am suggesting that Homo naledi is in the order of two million years old, with upper and lower limits of about 1.5 and 2.5 million years respectively.
Why is dating so important
Estimating the age of fossils is important because it allows palaeoanthropologists the opportunity to try to draw up a family tree. It shows the evolutionary relationships of distant relatives.
Some of the fossil species can be considered to represent possible ancestors of our own species, Homo sapiens, while other species such as Paranthropus robustus can be considered to be evolutionary “dead ends”.
The big question being asked is: where does Homo naledi fit in the evolutionary tree?
It had a small brain of about 500 cubic centimetres in volume. This makes it similar to fossils of Australopithecus. On the other hand, bones of parts of the skeleton, especially the foot, indicate that this species was in some respect remarkably like Homo.
Dating such enigmatic fossils is crucial for an understanding of evolutionary relationships of Homo naledi, compared to more than ten other species which are recognised by palaeontologists.
My approach has been to assess the degree of similarity or dissimilarity between skulls. This can help to assess the age and affinities of fossils.
Quantifying degrees of similarity between fossils
Recognising that the new fossils have features of both Australopithecus and Homo, we need to know how old they are. One way of addressing this is to use a technique that I have previously described, based on measurements of skulls.
Statistics are calculated by taking one set of measurements for specimen A, plotted against the corresponding measurements of specimen B. When A and B are the same species, the values for the two specimens are typically distributed along a straight line, with little scatter around that linear pattern.
When measurements of two specimens (C and D) of different species are plotted against each other, there is a high degree of scatter. The degree of scatter around the line can be quantified using a statistic that I have called log sem, based on a standard mathematical technique that is known as least squares linear regression.
Remarkably, a pattern has been found for comparisons of modern skulls of the same species, whether these are of mammals, birds or reptiles. The mean log sem value for comparisons of pairs of modern species has central tendency around a particular number with a value of -1.61 (plus or minus 0.1), which I have regarded as an approximation of a biological species constant called T.
How does this help to date Homo naledi
Comparisons have been made between the skull measurements of Homo naledi and those of more than ten other recognised species.
It is possible to say that Homo naledi is indeed different because in all cases the log sem statistics for such comparisons is significantly greater than -1.61.
But what is exciting is the fact that of all such comparisons, Homo naledi is most similar to skulls attributed to Homo habilis known to date to about 1.8 million years, and to some extent to other fossils attributed to Homo rudolfensis between about two and 2.5 million years ago.
To a smaller extent Homo naledi is similar to fossil skulls of Homo erectus between about 1.5 and 1.8 million years ago. Using these results, based on comparisons of skulls, I suggest that Homo naledi is two million years old, plus or minus 500,000 years.
The list, now in its 13th year, recognises the activism, innovation and achievement of the world’s most influential individuals.
As TIME editor, Nancy Gibbs, has said of the list in the past: "The TIME 100 is a list of the world's most influential men and women, not its most powerful, though those are not mutually exclusive terms. While power is certain, influence is subtle. As much as this exercise chronicles the achievements of the past year, we also focus on figures whose influence is likely to grow, so we can look around the corner to see what is coming."
Aus. sediba and H. naledi leads the way
Berger is an award-winning palaeoanthropologist, researcher, explorer, author and speaker from the Evolutionary Studies Institute at Wits University in Johannesburg. His explorations into human origins in Africa over the past two-and-a-half decades have resulted in many new and notable discoveries, including the most complete early hominin fossils found so far, which belong to a new species of early human ancestor, Australopithecus sediba, and, in 2013, the richest early hominin site yet found on the continent of Africa and a new species of human relative, Homo naledi, announced in 2015.
Tribute to African scientists
“It is an honour to be included in the TIME 100 and a tribute to the world-class and influential science being produced on the African continent by African scientists and African institutions such as Wits University. This recognition also reflects the hard work of my colleagues, who are and continue to be critical to both the discoveries being made, as well as the interpretations put forward in the scientific literature,” Berger says.
“Wits University continues again and again to produce high quality science that reaches and impacts on a global audience and I am thrilled to be part of that. New discoveries continue to be made by my colleagues and me at an ever increasing pace, and I hope, and indeed expect, that the research coming out of palaeoanthropology at Wits will continue to have a significant impact on science worldwide,” Berger adds.
Berger is also a National Geographic Explorer-in-Residence and the recipient of the National Geographic Society’s first Prize for Research and Exploration. He is a Fellow of the Royal Society of South Africa, a member of the Academy of Sciences of South Africa, and a Fellow of the Explorers Club. Among other positions, Berger serves on the advisory board of the Global Young Academy.
The full list and related tributes appear in the 2 May 2016 issue of TIME, available on newsstands on Friday, 22 April 2016, and now at time.com/time100.
Witsie made a NatGeo Emerging Explorer
- Wits University
Underground astronaut, Marina Elliott, says she is honoured to be part of this prestigious research programme.
She is one of 13 scientists from various countries who have been chosen to be part of this prestigious programme from the National Geographic Society that “recognises and supports uniquely gifted and inspiring scientists, conservationists, storytellers, and innovators—explorers who are already making a difference and changing the world”.
“It is an amazing honour, and especially humbling to be included in this year's cohort, as it is an incredibly diverse and talented group of people. It is exciting to be joining the National Geographic family, an amazing group of people, and an organisation that creates tremendous opportunities to reach people all over the world and make a difference through exploration, scientific research and education,” says Elliott.
The biological anthropologist is part of Wits University’s Rising Star Expedition team led by renowned palaeoanthropologist, Professor Lee Berger, who excavated the now famous Homo naledi – a new species of human ancestor and announced the landmark discovery during an international launch in 2015.
Elliott was one of the underground astronauts – a specialised group of six women Berger sourced through social media and who all fit the strict criteria of having to be tiny and small with specialised skills in caving and spelunking as well as excellent archaeological, palaeontological and excavation skills.
After the initial expedition, the Canadian joined the ESI where she continues to do research on H. naledi.
She plans to use the financial support and this recognition to promote science education in South Africa and around the world. “I am particularly interested in encouraging young girls and anyone who might not normally have access to educational and financial resources, to pursue studies in the sciences. I also want to promote scientific exploration by creating opportunities where people can develop skills and knowledge to go out and make discoveries of their own. There is so much more to discover!”
It is just exciting to realise that the great age of exploration isn’t over with, that there are places to explore and there are things to find. – Marina Elliott
Back to the future: Space-age exploration for pre-historic bones
- Wits University
The high-tech 3D mapping of Homo naledi’s Dinaledi chamber.
The extremely difficult conditions in which University of the Witwatersrand’s (Wits) Professor Lee Berger’s Rising Star team was forced to work, gave rise to the use of space-age technology to map the Dinaledi chamber and Rising Star Cave, in which over 1500 Homo naledi fossils were found.
Ashley Kruger, a PhD candidate in Palaeoanthropology at the Evolutionary Studies Institute at Wits, who was part of Berger’s initial Rising Star Expedition team, roped in the use of high-tech laser scanning, photogrammetry and 3D mapping technology to bring high resolution digital images to Berger and team members on an almost real-time basis in order to make vital decisions regarding the underground excavations.
“This is the first time ever, where multiple digital data imaging collection has been used on such a sale, during a hominin excavation,” says Kruger.
In 2013, after the discovery of the hominin assemblage, Berger put a call out for “skinny” explorers to join him on the expedition to excavate what became known as the Dinaledi Chamber, a cave system near the Sterkfontein Caves, about 40km North West of Johannesburg in South Africa. An all-female team of six “underground astronauts” were selected to undertake the underground excavation, due to the challenge of navigating a 12 meter vertical Chute, and passing through an 18 centimeter gap.
Berger himself was unable to go down into the chamber, which forced the team to introduce high-tech digital imaging techniques to virtually bring the exploration site to the surface.
Kruger and colleagues have now mapped the entire path of the Rising Star Cave, including the Dinaledi Chamber, both on the surface and underground, using a combination of aerial drone photography, high-resolution 3D laser scanning, a technique called white-light source photogrammetry, and conventional surveying techniques. The research paper, Multimodal spatial mapping and visualisation of Dinaledi Chamber and Rising Star Cave was published in the scientific journal, the South African Journal of Science, on Friday.
“The 3D scans of the cave and excavation area helped scientists above ground immensely in making decisions about the next step to take with regards to excavations,” says Dr. Marina Elliot, Rising Star excavation manager, and co-author of the paper.
“These methods provided researchers with a digital representation of the site from landscape level right down to individual bones,” says Kruger.
The precise digital reconstruction of the Rising Star Cave provides new insights into the Dinaledi Chamber’s structure and location, as well as the exact location of the fossil site. It also paints a detailed picture of the challenges that the underground astronauts had to deal with in navigating the caves on a daily basis for over five weeks in November 2013 and March 2014.
“We realise now, through the use of high-resolution scanning that the Dinaledi chamber is about 10 meters deeper than we originally thought,” says Kruger. This is important in understanding the processes which may have aided the site’s formation.
Kruger’s paper is the first of a number of papers due to be published on the spatial understanding of the Homo naledi site within the Dinaledi chamber. The rest of his research aims to provide answers about how the site formed, what the position of the fossils can tell researchers, as well as to paint a more detailed picture on how the hominin bodies came to be in the cave.
How tiny black spots shed light on part of the Homo naledi mystery
- Francis Thackeray
Many questions have been thrown up by the discovery in South Africa of a previously unidentified human relative, Homo naledi.
Perhaps the one that’s grabbed people’s attention the most is how Homo naledi’s bones ended up in the Dinaledi Chamber in the Rising Star cave complex in the Cradle of Humankind near Johannesburg.
The team which found and classified the remains has suggested that the Homo naledi group deliberately deposited carcasses in complete darkness at the very back of the cave system. According to this claim, Homo naledi adopted a relatively “modern” or ritualistic form of behaviour even though the species had smaller brains than today’s humans.
To date, no opening has been found within the Dinaledi Chamber. But might there have been an entrance at some time in the past? New research I have conducted and published in the South African Journal of Science centred on mysterious black spots found on Homo naledi bones from the cave. My findings suggest that the answer to this question may have been “yes” – there very well may have been an entrance.
I strongly believe that there was possibly a temporary entrance into the chamber, in addition to the one used by explorers today. This temporary entrance may been covered up by a rock fall that also trapped the individuals whose bones were found some time later.
Why do I believe that in fact there was this additional opening to the cave? Because those mysterious black spots are manganese dioxide and were probably deposited on the bones by lichen. And lichen need light to grow – so there must have been some light penetrating into the Dinaledi chamber. My scenario is that the Homo naledi family group was trapped in the Dinaledi Chamber after a rockfall – but that there was still, for a time, enough light to penetrate the chamber. This allowed lichen to grow on many of the bones of Homo naledi.
Then, with subsequent rockfalls in a phreatic maze, the Dinaledi Chamber was sealed except for the difficult route whereby explorers can enter the cave at the present time.
Evidence from elsewhere
The team which discovered the remains noted that “some bones and teeth are dotted with black iron-manganese oxy-hydroxide deposits and coatings”.
I examined the remains in question and found that the spots were analogous to the kind of associated with modern lichen which are “symbionts”, including fungi – that disperse in spots – and algae, which require at least some light to grow.
My colleagues and I have previously examined instances of lichen in the Cradle of Humankind area. Lichen can grow on certain substrates, including bone or rock, with a dotted or spotted distribution. The spotted distribution of lichen is sometimes associated with dotted distributions of manganese oxy-hydroxide on the same surfaces.
The source of the manganese in the Cradle of Humankind region would include dolomite and chert. These are rock materials that date back two billion years ago, related to a shallow saline sea that existed at that time.
In the Cradle of Humankind lichen has proved to grow not only on chert, but also on dolomite. It can also grow on bone surfaces.
Hominid cranial specimens from the nearby Sterkfontein caves have small dots or spots of manganese oxyhydroxide on surfaces of bone, even within the inner cranial wall of these skulls. It seems likely that these dots or spots of manganese oxyhydroxide may have been areas where lichens were able to grow – in a partially sunlit micro-environment – for a relatively short period of time. Then sand would have covered the crania, blocking out the light and halting the lichen’s ability to keep growing.
So what does such evidence in the Cradle of Humankind tell us about Homo naledi’s mysterious black spots?
Secrets of the caves
The circumstances in the Wonder Cave – which is within 10kms of the Rising Star cave complex – offer some important clues to what might have happened to create spots on the Homo naledi remains.
When one walks from the entrance of the cavern into the darkness of the dolomitic solution cavity, the following becomes obvious:
Where there is intense light and heat on dry exposed surfaces outside the cave, there is little or no lichen growth at all. But, in the moister and slightly darker regions of the cave, there is an area where light and moisture appear to be optimal for the present lichen colonists.
Then, in the darkness at the back of the cave where very little light penetrates, there’s a decrease in the mean size of lichens, until there is no lichen growth at all – although there may be some moisture because of water dripping through the phreatic maze of the dolomitic cave system.
All of this suggests that, for the Homo naledi bones in the Rising Star cave to have become spotted with manganese dioxide, they had to have some exposure to light. That could only have happened if light got into the cave. And this was only possible if there was some sort of entrance that has, in the distant past, been covered over. If correct, this would contradict the original team’s proposal that, in prehistory, the Dinaledi Chamber could only be accessed by means of very narrow and circuitous passages, in complete darkness.
Time to reassess?
Based on my findings I believe that there was, at some time, a second entrance to the Dinaledi Chamber. This allowed at least some light to penetrate into the cave and to facilitate the growth of lichen and the subsequent deposition of manganese oxyhydroxide on the Homo naledi bones.
I’d further hypothesise that such an entrance, if it existed at all, was temporary. A rockfall in the maze cave system may have subsequently sealed the entrance at some stage in the dolomitic solution cavity. The darkness that settled over the cave would have terminated any lichen growth.
If there was more than one entrance into the Dinaledi Chamber, as suggested by my work and research conducted by Dr Aurore Val, the “intentional depositional model” will need to be reassessed. It would seem unlikely that the Homo naledi group deliberately deposited or buried its dead.
Author’s note: I would like to acknowledge the support of the National Research Foundation, the Andrew Mellon Foundation, and the Centre of Excellence for the Palaeosciences.
Four new papers on different aspects of the anatomy of Homo naledi have been published, and more papers are coming soon, all led by early career researchers.
This has been a great couple of weeks for our team researching the Rising Star fossil discoveries.
We are looking back on the close of the first field expedition three years ago, and the Journal of Human Evolution has just published four new papers describing different aspects of the anatomy of Homo naledi, including the skull, leg, and upper limb. More new papers are coming soon, all led by early career researchers.
I want to take a moment to recognize the outstanding work and to talk about some lessons we have learned in this process.
When we designed a plan to analyze the fossils by involving many early career scientists, we faced many doubters. Some expressed their concerns in public, others spoke with us privately. There was one common thread: Surely with such an important discovery, we should only allow the best, most experienced experts to study the fossils. How could scientists early in their careers possibly match the quality of work attained by experts who have been studying fossils for more than 40 years?
From the beginning this so-called concern was laughable. Forty years ago, when today's most senior experts got their start, it was because Mary Leakey, Richard Leakey, Clark Howell (and again Clark Howell), and others invited students and young researchers to join their work describing new hominin fossils. Somehow people have forgotten our field’s history.
Experimental science engages people at every career level. When you look at astronomy, at high-energy physics, at genomics, at clinical research, you see enormous energy and expertise developed by graduate students, postdocs, and emerging principal investigators (PIs), who work as teams to develop the newest techniques.
Description of fossils is a technical exercise, and today we employ a range of methods that did not exist 40 years ago. This is not an art: what makes it credible is not whether you are an old master, but whether other people can see and replicate what you have done. Twenty skilled sets of eyes beat one set every time.
We did not start the Rising Star work from zero. After discovering and describing A. sediba, Lee began to broaden the pool of experts, including many early career scientists, both South African and international researchers. Over five years, they published a remarkable 15 papers in Science and Nature, seven led by early career authors. Many of them would become core members of the team for Rising Star.
From there, the Rising Star Workshop was an easy leap, bringing people together for five weeks to build the most detailed formal diagnosis of a new hominin species ever published. They put in more than 10,000 hours of work in the laboratory, building a more complete record of the anatomy of H. naledi than we have for any extinct hominin population other than the Neanderthals.
The evidence changed the way our team thought about the function of fossil anatomy and the course of the evolutionary process. So after running the marathon of diagnosing the new species, they signed up for the Ironman triathlon. They submitted a series of manuscripts, all led by early career researchers, to the premier, most highly-cited and respected trade journal in the field of anthropology, the Journal of Human Evolution. No one in the field would dispute that the editorial board and reviewer panels of JHE have the highest scientific rigor. These papers have been as strongly vetted as any research ever published in paleoanthropology.
I emphasize this point because a few critics have said we are “rushing the science,” saying that no one can understand a fossil sample without many years of secret research.
This is a false choice. Great research programs do last years, and ours undoubtedly will continue for decades. But great research programs submit incremental work to the broader inspection of the scientific community through publication and review. Artists may work on a masterpiece in secret for years, but scientists do not.
We are moving forward on a solid foundation, now approaching 400 pages of peer-reviewed research in some of the highest-impact journals in general science and in the field of anthropology. All of this research has been conducted within three years after the initial discovery of the Dinaledi Chamber. The papers on H. naledi have already been cited more than 140 times. With the data now accessible to the public, other scientists and students have replicated our work in classrooms all over the world.
One of the biggest winners in this process has been the National Research Foundation of South Africa, which provided much of the funding for the Rising Star Workshop. Comparing cost to output, the workshop is already one of the most productive investments in the history of paleoanthropology, and it will continue to pay dividends. In 2014, NRF recognized our team with its award for Team Science. Earlier this year, the Wenner-Gren Foundation helped to fund a workshop led by our early career scientists working on the Dinaledi dental remains, including a new group of senior and early career scientists. Funding organizations are recognizing that this experimental model is the right one to produce great science.
It is also right for boosting careers. At least four of our early career participants have been promoted to tenured positions, at least seven have moved into new tenure-stream jobs. Since the project began, six students have moved into new postdocs, and three have moved into other non-tenure-stream research or teaching positions. We began with 14 students, 10 have defended their PhDs. Those already in tenure-stream positions have achieved enormous public impact for their work. In this South African-led project, it is important that the South African participants have achieved these career outcomes as successfully as the international scientists, and many of the international scientists have committed to continuing research partnerships in South Africa or have relocated here.
We selected scientists with a demonstrated record of research, who were already successful by any standard, so some of the positive outcomes would have happened to them anyway. But I think it is obvious that universities and institutions are making new investments in these scholars because they are poised to lead the next generation of human evolutionary science. Their accomplishments together are showing the way forward.
What works for the early career participants also has worked for the more senior members of the team. Some have won promotion to full professor or to distinguished professorships, many have received prestigious awards and grants, and all have seen a tremendous outpouring of interest from the public. They have increased the profile of paleoanthropology within the scientific community, and that new profile will lead to greater research support for the field. For me, the chance to work with this team of brilliant scientists, getting to know the future stars of human evolution, has been an honor.
This is a time to celebrate success. The Rising Star discoveries have yielded some real surprises for understanding human evolution, and the work continues to reward us with new insights.
More discoveries are coming.
Young Homo naledi surprises
- Wits University
250 000 year old species from Rising Star Cave raises more questions about our origins.
The Rising Star Cave system in South Africa has revealed yet more important discoveries, only a year and a half after it was announced that the richest fossil hominin site in Africa had been discovered, and that it contained a new hominin species named Homo naledi by the scientists who described it.
The age of the original Homo naledi remains from the Dinaledi Chamber has been revealed to be startlingly young in age. Homo naledi, which was first announced in September 2015, was alive sometime between 335 and 236 thousand years ago. This places this population of primitive small-brained hominins at a time and place that it is likely they lived alongside Homo sapiens. This is the first time that it has been demonstrated that another species of hominin survived alongside the first humans in Africa.
The research, published today in three papers in the journal eLife, presents the long-awaited age of the naledi fossils from the Dinaledi Chamber and announces the new discovery of a second chamber in the Rising Star cave system, containing additional specimens of Homo naledi. These include a child and a partial skeleton of an adult male with a remarkably well-preserved skull.
The new discovery and research was done by a large team of researchers from the University of the Witwatersrand (Wits) (South Africa), James Cook University (Australia), the University of Wisconsin (Madison, United States), and more than 30 additional international institutions have today announced two major discoveries related to the fossil hominin species Homo naledi.
The team was led by Professor Lee Berger of the Evolutionary Studies Institute at Wits University in Johannesburg, South Africa, and a National Geographic Explorer in Residence. The discovery of the second chamber with abundant Homo naledi fossils includes one of the most complete skeletons of a hominin ever discovered, as well as the remains of at least one child and another adult. The discovery of a second chamber has led the team to argue that there is more support for the controversial hypothesis that Homo naledi deliberately disposed of its dead in these remote, hard to reach caverns.
The naledi date is surprisingly recent. The fossil remains have primitive features that are shared with some of the earliest known fossil members of our genus, such as Homo rudolfensis and Homo habilis, species that lived nearly two million years ago. On the other hand, however, it also shares some features with modern humans. After the description of the new species in 2015, experts had predicted that the fossils should be around the age of these other primitive species. Instead, the fossils from the Dinaledi Chamber are barely more than one-tenth that age.
“The dating of naledi was extremely challenging,” noted Dirks, who worked with 19 other scientists from laboratories and institutions around the world, including labs in South Africa and Australia, to establish the age of the fossils. “Eventually, six independent dating methods allowed us to constrain the age of this population of Homo naledi to a period known as the late Middle Pleistocene.”
The age for this population of hominins shows that Homo naledi may have survived for as long as two million years alongside other species of hominins in Africa. At such a young age, in a period known as the late Middle Pleistocene, it was previously thought that only Homo sapiens (modern humans) existed in Africa.
More critically, it is at precisely this time that we see the rise of what has been called “modern human behaviour” in southern Africa – behaviour attributed, until now, to the rise of modern humans and thought to represent the origins of complex modern human activities such as burial of the dead, self-adornment and complex tools.
The team used a combination of optically stimulated luminescence dating of sediments with Uranium-Thorium dating and palaeomagnetic analyses of flowstones to establish how the sediments relate to the geological timescale in the Dinaledi Chamber.
Direct dating of the teeth of Homo naledi, using Uranium series dating (U-series) and electron spin resonance dating (ESR), provided the final age range. “We used double blinds wherever possible,” says Professor Jan Kramers of the University of Johannesburg, a uranium dating specialist.
Dr Hannah Hilbert-Wolf, a geologist from James Cook University who also worked on the Dinaledi Chamber, noted that it was crucial to figure out how the sediments within the Dinaledi Chamber are layered, in order to build a framework for understanding all of the dates obtained.
“Of course we were surprised at the young age, but as we realised that all the geological formations in the chamber were young, the U-series and ESR results were perhaps less of a surprise in the end,” added Professor Eric Roberts, from James Cook University and Wits, who is one of the few geologists to have ever entered the Dinaledi Chamber, due to the tight 18cm-wide constraints of the entrance chute.
Dr Marina Elliott, Exploration Scientist at Wits and one of the original “underground astronauts” on the 2013 Rising Star Expedition, says she had always felt that the naledi fossils were ‘young’. “I’ve excavated hundreds of the bones of Homo naledi, and from the first one I touched, I realised that there was something different about the preservation, that they appeared hardly fossilised.”
Homo naledi’s significant impact
In an accompanying paper, led by Berger, entitled Homo naledi and Pleistocene hominin evolution in subequatorial Africa, the team discusses the importance of finding such a primitive species at such a time and place. They noted that the discovery will have a significant impact on our interpretation of archaeological assemblages and understanding which species made them.
“We can no longer assume that we know which species made which tools, or even assume that it was modern humans that were the innovators of some of these critical technological and behavioural breakthroughs in the archaeological record of Africa,” says Berger. “If there is one other species out there that shared the world with ‘modern humans’ in Africa, it is very likely there are others. We just need to find them.”
John Hawks of the University of Wisconsin-Madison and Wits University, an author on all three papers, says: “I think some scientists assumed they knew how human evolution happened, but these new fossil discoveries, plus what we know from genetics, tell us that the southern half of Africa was home to a diversity that we’ve never seen anywhere else”.
“Recently, the fossil hominin record has been full of surprises, and the age of Homo naledi is not going to be the last surprise that comes out of these caves I suspect,” adds Berger.
“The chamber, which we have named the Lesedi Chamber, is more than a hundred meters from the Dinaledi Chamber. It is almost as difficult to access, and also contains spectacular fossils of naledi, including a partial skeleton with a wonderfully complete skull,” says Hawks, lead author on the paper describing the new discovery. Fossil remains were first recognised in the chamber by Rick Hunter and Steven Tucker in 2013, as fieldwork was underway in the Dinaledi Chamber.
The name “Lesedi” means “light” in the Setswana language. Excavations in the Lesedi Chamber began later, and would take nearly three years.
No easy access
“To access the Lesedi Chamber is only slightly easier than the Dinaledi Chamber,” says Elliott, who was lead excavator of the fossils from the new locality. “After passing through a squeeze of about 25cm, you have to descend along vertical shafts before reaching the chamber. While slightly easier to get to, the Lesedi Chamber is, if anything, more difficult to work in due to the tight spaces involved.”
Hawks points out that while the Lesedi Chamber is “easier” to get into than the Dinaledi Chamber, the term is relative. “I have never been inside either of the chambers, and never will be. In fact, I watched Lee Berger being stuck for almost an hour, trying to get out of the narrow underground squeeze of the Lesedi Chamber.” Berger eventually had to be extracted using ropes tied to his wrists.
The presence of a second chamber, distant from the first, containing multiple individuals of Homo naledi and almost as difficult to reach as the Dinaledi Chamber, gives an idea of the extraordinary effort it took for Homo naledi to reach these hard-to-get-to places, says Hilbert-Wolf.
“This likely adds weight to the hypothesis that Homo naledi was using dark, remote places to cache its dead,” says Hawks. “What are the odds of a second, almost identical occurrence happening by chance?”
So far, the scientists have uncovered more than 130 hominin specimens from the Lesedi Chamber. The bones belong to at least three individuals, but Elliot believes that there are more fossils yet to be discovered. Among the individuals are the skeletal remains of two adults and at least one child. The child is represented by bones of the head and body and would likely have been under five years of age. Of the two adults, one is represented by only a jaw and leg elements, but the other is represented by a partial skeleton, including a mostly complete skull.
Neo, an archaeological gift
The team describes the skull of the skeleton as “spectacularly complete”.
“We finally get a look at the face of Homo naledi,” says Peter Schmid of Wits and the University of Zurich, who spent hundreds of hours painstakingly reconstructing the fragile bones to complete the reconstruction.
The skeleton was nicknamed “Neo” by the team, chosen for the Sesotho word meaning “a gift”.
“The skeleton of Neo is one the most complete ever discovered, and technically even more complete than the famous Lucy fossil, given the preservation of the skull and mandible,” says Berger.
The specimens from the Lesedi Chamber are nearly identical in every way to those from the Dinaledi Chamber, a remarkable finding in and of itself.
“There is no doubt that they belong to the same species,” says Hawks.
The Lesedi Chamber fossils have not been dated yet, as dating would require destruction of some of the hominin material. “Once described, we will look at the way forward for establishing the age of these particular fossils,” says Dirks. Elliot adds, however, that as the preservation and condition of the finds are practically identical to that of the naledi specimens from the Dinaledi Chamber the team hypothesizes that their age will fall roughly within the same time period.
Decades of research still ahead
Berger believes that with thousands of fossils likely remaining in both the Lesedi and Dinaledi Chambers, there are decades of research potential. “We are going to treat ongoing extraction of material from both of these chambers with extreme care and thoughtfulness and with the full knowledge that we need to conserve material for future generations of scientists, and future technological innovations,” he says.
52 scientists from 35 departments and Institutions were involved in the research.
Wits Vice-Chancellor and Principal, Professor Adam Habib said: “The search for human origins on the continent of Africa began at Wits and it is wonderful to see this legacy continue with such important discoveries”
“The National Geographic Society has a long history of investing in bold people and transformative ideas,” said Gary E. Knell, president and CEO of the National Geographic Society that funded the expeditions that recovered the fossils and established their age. “The continued discoveries from Berger and his colleagues showcase why it is critical to support the study of our human origins and other pressing scientific questions.”
This exhibit of the largest display of original fossil hominin material in history forms part of an exhibition called “Almost Human”.
The exhibition will be housed in ‘The Gallery’ – a state-of-the-art exhibition space built as part of the Gauteng Infrastructure Upgrade Project. This is the second completed construction, the first being the upgrade to the Hominin House facilities at Maropeng.