Homo naledi is a species of extinct hominin discovered in 2013 deep inside the Rising Star Cave system in South Africa, and nearly everything about it has defied expectation. With a brain roughly a third the size of ours yet a body that walked upright and hands capable of gripping tools, it scrambles the tidy narrative that bigger brains drove the major leaps in human evolution. More jarring still, dating work published in 2017 showed that this small-brained species lived between roughly 236,000 and 335,000 years ago, meaning it overlapped in time and geography with the earliest Homo sapiens in Africa. That overlap, along with contested claims that H. naledi may have buried its dead and even engraved geometric marks on cave walls, has turned this species into one of the most debated topics in paleoanthropology.
A Body Built From Contradictions
If you lined up a Homo naledi skeleton next to a modern human’s, the lower half would look surprisingly familiar. The foot was well adapted for striding bipedalism, with a big toe aligned alongside the other toes much like ours, an elongated midfoot, and modern-looking ankle joints. The lower limbs were long relative to body size, reinforcing the picture of a creature that walked efficiently on two legs across open ground.1Nature Communications. The foot of Homo naledi From the waist up, things get stranger. The ribcage was narrow and the vertebrae small, with robust, relatively uncurved lower ribs that recall earlier hominins adapted to climbing and processing lower-quality plant foods.2Journal of Human Evolution. The vertebrae and ribs of Homo naledi The shoulders were oriented more like those of an ape than a human, and the fingers were strongly curved, both features associated with frequent climbing.
The hands tell a particularly interesting story. The wrist and thumb were shaped much like those of modern humans and Neanderthals, built for precision gripping of the kind needed for tool use. Yet those same hands had curved finger bones that suggest the species still spent meaningful time climbing in trees or along rock faces.3Nature Communications. The hand of Homo naledi A 2025 study examining the internal bone structure of H. naledi finger bones confirmed that these curved phalanges were not just evolutionary leftovers. The cortical bone distribution indicated active climbing behavior, distinct from the patterns seen in the earlier hominin Australopithecus sediba, meaning H. naledi had its own specific way of using its hands for both dexterous manipulation and vertical movement.4PubMed Central. Phalangeal cortical bone distribution reveals different dexterous and climbing behaviors in Australopithecus sediba and Homo naledi
Then there is the brain. Endocranial volumes for H. naledi range from about 465 to 560 cubic centimeters, which puts it in the same ballpark as Australopithecus, a genus that lived millions of years earlier.5PubMed. Body size, brain size, and sexual dimorphism in Homo naledi from the Dinaledi Chamber For context, the average modern human brain is roughly 1,350 cc, so H. naledi’s was roughly a third of that. But brain size alone misses something important. When researchers made virtual casts of the inside of H. naledi skulls, they found that the frontal lobe was organized in ways that resemble larger-brained Homo species like Homo erectus and Homo habilis, not the great apes or australopiths you would expect from a brain that small.6PubMed Central. Endocast morphology of Homo naledi from the Dinaledi Chamber, South Africa The implication is striking: reorganization of the prefrontal cortex, the region associated with planning, social cognition, and complex behavior, happened independently of the dramatic brain-size increases seen in other branches of the human family tree.7Human Development. The Co-Evolution of the Prefrontal Cortex and Human Childhood: Evidence from Paleoneurology and Development
Why the Dating Changed Everything
When H. naledi was first announced in 2015, no age had been established for the fossils. Many researchers assumed the species must be ancient, perhaps one or two million years old, given its small brain and primitive upper body. The 2017 dating results were a shock. Multiple independent techniques, including uranium-series dating of flowstones that directly encased some bones, converged on an age between roughly 236,000 and 335,000 years ago for the Dinaledi Chamber fossils.8PubMed Central. The age of Homo naledi and associated sediments in the Rising Star Cave, South Africa That places H. naledi squarely in the late Middle Pleistocene, an era when Homo sapiens was already emerging in Africa and Middle Stone Age tools were being crafted by larger-brained populations elsewhere on the continent.
The coexistence of H. naledi and early H. sapiens in southern Africa is not just a curiosity. It raises real questions about how multiple hominin species shared landscapes and whether they interacted, competed for resources, or simply occupied different ecological niches. Researchers have used the overlap as a case study for modeling how a small-brained hominin might have carved out a distinct technological and ecological role alongside a more cognitively advanced species.9Journal of Archaeological Method and Theory. Constraining the Likely Technological Niches of Late Middle Pleistocene Hominins with Homo naledi as Case Study This is a scenario with no modern parallel. Today we are the only surviving hominin, but for most of human evolutionary history, multiple species coexisted. H. naledi is a vivid reminder of that reality.
What H. naledi Ate
Two independent lines of dental evidence point toward a diet heavy in tough, hard, or gritty foods. Microscopic analysis of wear patterns on H. naledi teeth revealed surface textures dominated by large, deep pits, the kind left behind by foods that require serious crushing force. Among all known fossil hominins, only Paranthropus robustus, a species famous for its massive chewing apparatus, showed higher average texture complexity. The closest matches among living primates were a West African monkey that specializes in cracking hard-shelled foods and a generalist baboon.10PubMed. Brief communication: Dental microwear and diet of Homo naledi This suggests H. naledi regularly consumed hard items like nuts or underground storage organs such as tubers.
A separate study looking at overall tooth shape rather than surface wear added nuance. H. naledi teeth are smaller than those of Australopithecus and Paranthropus but are higher-crowned and more resistant to wear, a design suited for processing abrasive foods over a long period. The teeth also show heavy chipping. Taken together, the evidence suggests H. naledi was eating foods with similar toughness to what earlier hominins consumed but was encountering more grit and dust in the process, perhaps because it was foraging in open or disturbed environments rather than dense forest.11PubMed. Dental topography and the diet of Homo naledi
Growing Up as Homo naledi
Teeth preserve a detailed record of how an individual developed, because enamel lays down regular growth lines as it forms, much like tree rings. Studying these in H. naledi has produced yet another mosaic picture. A juvenile specimen from the Dinaledi Chamber showed a sequence of tooth development in which premolars and second molars emerged in a human-like order. But the roots of those second molars were only about half-formed at the time of gum emergence, closer to what you see in chimpanzees, where human children typically have around three-quarters of root length formed at the same stage.12PubMed Central. Dental development in Homo naledi The species does not fit cleanly into a “human” or “ape” developmental box.
A broader analysis of growth patterns in H. naledi’s front teeth reinforced this picture of developmental uniqueness. The distribution of fine growth lines on the enamel surface, combined with the total number of those lines, gave H. naledi a distinctive signature. In statistical classification, about two-thirds of H. naledi teeth were correctly identified as their own species, while the remaining third were most likely to be mistaken for those of modern humans, particularly southern African populations. What set H. naledi apart from most other hominins was a strongly skewed pattern of enamel growth combined with moderate overall growth-line counts.13PubMed. Patterns of lateral enamel growth in Homo naledi as assessed through perikymata distribution and number A separate study focusing on whether H. naledi enamel grew in a human-like or ape-like fashion confirmed that the species displayed human-like enamel growth patterns, adding one more human trait to this small-brained species’ surprising resume.14PubMed. Human-like enamel growth in Homo naledi
Did Homo naledi Bury Its Dead?
This is the claim that has generated the most public fascination and the most scientific pushback. The Rising Star Cave system is extraordinarily difficult to access. The Dinaledi Chamber, where the first trove of H. naledi fossils was found, lies at the end of a narrow chute barely 18 centimeters wide in places, deep underground with no evidence of an ancient entrance that would have been easier to navigate. No stone tools, no animal bones from predators or scavengers, and no evidence of water transport that could have washed the remains in have been found alongside the hominin bones. The research team led by Lee Berger has argued that the most plausible explanation is deliberate body disposal: H. naledi carried its dead into the deep cave on purpose.
In 2023 and subsequent publications, the team went further, describing what they interpreted as evidence of mortuary practices and even symbolic behavior. Explorations in the Dinaledi Subsystem yielded features described as some of the earliest evidence of mortuary practice in hominins.15PubMed Central. Meaning-making behavior in a small-brained hominin, Homo naledi, from the late Pleistocene: contexts and evolutionary implications Additionally, researchers reported geometric engravings on the dolomitic limestone walls of the cave: deeply incised lines, cross-hatchings, and other shapes on a pillar in the Hill Antechamber, which they attributed to H. naledi.16PubMed Central. An initial report of circa 241,000- to 335,000-year-old rock engravings and their relation to Homo naledi in the Rising Star cave system, South Africa
These are extraordinary claims, and many paleoanthropologists have said the evidence does not yet support them. A detailed critique published in the Journal of Human Evolution argued that there is no scientific evidence that H. naledi buried its dead or produced rock art, calling for alternative explanations to be more thoroughly ruled out. A 2024 review in Nature Ecology and Evolution noted that while the discovery of the species itself is well established, “almost everything else claimed about H. naledi—its age, burial context and behaviour—has been controversial.”17Nature Ecology & Evolution. What we know and do not know after the first decade of Homo naledi The geological evidence does show that cave sediments formed under dry, non-flooded conditions through processes like drying, cracking, and gravitational slumping of mud deposits rather than water transport.18Sedimentology. Formation of mud clast breccias and the process of sedimentary autobrecciation in the hominin‐bearing (Homo naledi) Rising Star Cave system, South Africa That rules out one alternative (that rushing water deposited the bodies), but it does not confirm intentional burial. Some fossils show evidence of post-depositional movement through the sediment as debris slumped toward floor drains, complicating the interpretation of how the bodies were originally positioned.
The debate matters because of what is at stake. If a hominin with a brain one-third the size of ours was deliberately disposing of its dead and producing symbolic markings, that would fundamentally reshape our understanding of what brain size has to do with complex behavior. The proponents are aware of this, and so are the skeptics. Both sides agree that the cave access was genuinely difficult and that the bone accumulation is unusual. Where they disagree is on whether deliberate disposal is the only viable explanation and whether the engravings are truly human-made rather than natural features of weathered rock. This will likely remain contentious until additional caves, additional species, or additional dating evidence tips the balance.
Where Homo naledi Fits on the Family Tree
Placing H. naledi among its relatives has proven almost as contentious as the burial debate, if less headline-grabbing. Phylogenetic analyses using skull and tooth measurements consistently support the conclusion that H. naledi belongs within the genus Homo rather than with Australopithecus, and that it clusters with other Homo species and the transitional species Australopithecus sediba. But pinning down exactly where within that group is harder. Statistical analyses could not rule out a close relationship with Homo habilis, Homo erectus, Homo floresiensis, Homo antecessor, Homo sapiens, or Au. sediba. Several hypothesized positions were rejected, but multiple others remained plausible.19PubMed. The evolutionary relationships and age of Homo naledi: An assessment using dated Bayesian phylogenetic methods
Part of the difficulty is that H. naledi’s mosaic anatomy sends contradictory phylogenetic signals. Its brain size pulls it toward Australopithecus, its frontal lobe organization pulls it toward later Homo, its feet pull it toward modern humans, and its shoulders and fingers pull it toward much earlier climbing ancestors. This mix makes it genuinely hard to tell whether H. naledi represents a very early branch of Homo that survived in isolation for a long time, retaining primitive features while independently evolving some modern traits, or whether it is more closely related to later species than its brain size would suggest. The young geological age adds to the puzzle: a species living 250,000 years ago with anatomy that resembles forms from two million years ago could either be a relict population or a lineage we simply have not sampled well enough to understand.
Proteins Preserved in Ancient Teeth
One of the most technically exciting recent developments involves the recovery of ancient proteins from H. naledi tooth enamel. A 2025 study published in Cell reported that amino acid analysis of enamel from four H. naledi specimens showed that the protein within the enamel had remained in a closed system, retaining endogenous peptides with less degradation than samples from other extinct hominins recovered at the nearby Swartkrans site, consistent with H. naledi’s younger geological age.20Cell. Enamel proteins reveal biological sex and genetic homogeneity in Homo naledi The protein preservation was good enough to determine the biological sex of the individuals and to investigate genetic relationships within the group.
This matters for several reasons. Ancient DNA has not yet been recovered from H. naledi, and given the warm, wet conditions of South African caves, it may never be. Proteins degrade more slowly than DNA and can survive in environments where genetic material cannot. The fact that enamel proteins are well preserved in H. naledi opens a window into the biology of a species that might otherwise remain genetically invisible. If future proteomic work can be expanded to more specimens, it could help clarify the relationships among the individuals in the cave, whether they represent a single population or multiple depositional events, and ultimately where H. naledi sits in the broader hominin family tree at a molecular level.
Why One Species Rewrites So Many Assumptions
Before H. naledi, the dominant framework in paleoanthropology treated human evolution as a roughly linear progression in which brain size, body proportions, diet, and behavior all advanced in tandem. Bigger brains came with smaller teeth, more gracile bodies, better tools, and eventually symbolic thought. H. naledi violates almost every element of that package. It has a small brain with a reorganized frontal cortex. It has modern-looking feet paired with a climbing-adapted upper body. It has human-like tooth development sequences with ape-like root growth timing. It ate hard, gritty foods with teeth smaller than those of earlier hominins but tougher-crowned and more chip-prone. And it may, depending on which researchers you ask, have been capable of behaviors once thought to require a much larger brain.
The sheer number of fossils is part of what makes H. naledi so valuable. The Dinaledi Chamber alone yielded over 1,500 specimens representing at least 15 individuals, making it one of the largest single assemblages of any fossil hominin species. A second chamber, the Lesedi Chamber, added more. This abundance means researchers can study variation within the species, examine development from juveniles to adults, and perform destructive analyses like sectioning teeth or extracting proteins without exhausting the available material. Most fossil hominin species are known from a handful of fragments. H. naledi has given researchers enough material to ask the kinds of detailed questions that usually only get answered for living species.
The species also serves as a natural experiment in evolutionary biology. Because it retained features spread across millions of years of hominin evolution all in one body, it demonstrates that evolution does not move in lockstep. Different parts of the skeleton, different organ systems, and different aspects of development can evolve at different rates and in response to different pressures. The frontal lobe can reorganize without the rest of the brain enlarging. The foot can become fully bipedal while the hand retains powerful climbing adaptations. Tooth enamel can grow in a human-like pattern while root formation stays ape-like. That kind of mosaic evolution was theoretically predicted but rarely illustrated so vividly by a single species.
The Cave Itself as a Puzzle
The Rising Star Cave system sits within the Cradle of Humankind, a UNESCO World Heritage Site northwest of Johannesburg that has produced hominin fossils for over a century. But the specific chambers where H. naledi was found are unlike typical fossil sites. The Dinaledi Chamber sits roughly 30 meters underground and is reached only through a narrow vertical chute called the Superman’s Crawl followed by a climb up a feature known as the Dragon’s Back. The passage narrows to as little as 18 centimeters at one point. In the initial excavation, only researchers slim enough to fit through the slot could access the chamber.
The sediments inside the cave formed through a process called sedimentary autobrecciation, in which thin layers of mud dried, cracked, broke apart, and were then reworked by gravity and microbial activity under dry cave conditions.18Sedimentology. Formation of mud clast breccias and the process of sedimentary autobrecciation in the hominin‐bearing (Homo naledi) Rising Star Cave system, South Africa The fossils are embedded within these angular mud clast deposits, and some have been repositioned over time as sediment slumped toward low points in the chamber floor. Manganese staining on some fossil surfaces provides cross-cutting evidence of this post-depositional movement. Understanding these geological processes is critical to interpreting the site, because the way the bones came to rest affects every argument about how they got there in the first place.
Whether or not H. naledi intentionally entered these deep recesses, the cave environment is what preserved the fossils so well. The stable temperature and humidity deep underground slowed chemical degradation, which is why enamel proteins survived for a quarter of a million years in a tropical latitude where DNA has so far been unrecoverable. The very inaccessibility that makes the burial hypothesis so provocative is also what kept predators, scavengers, and weathering at bay, creating one of the richest and best-preserved hominin fossil deposits in Africa.