Homo naledi was a small-brained, small-bodied species of the genus Homo that lived in southern Africa between roughly 236,000 and 335,000 years ago, making it a contemporary of early Homo sapiens rather than a distant ancestor. Discovered in 2013 deep inside the Rising Star cave system near Johannesburg, it is one of the most puzzling additions to the human family tree: a creature with a brain barely larger than a chimpanzee’s, shoulders built for climbing, hands that could both grip tree branches and manipulate objects with precision, and feet that walked upright much like yours do. What makes Homo naledi truly strange is not any single trait but the combination, and the fierce debate its discoverers ignited by suggesting that this small-brained species may have deliberately disposed of its dead and even engraved symbols on cave walls.
How Homo Naledi Was Found
In 2013, two recreational cavers exploring the Rising Star cave system, located about 40 kilometers northwest of Johannesburg in the Cradle of Humankind, squeezed through a narrow gap and dropped into a remote chamber littered with bones. The chamber, later named the Dinaledi Chamber, could only be reached by navigating a 12-meter vertical chute and passing through an opening just 18 centimeters wide. When paleoanthropologist Lee Berger learned of the find, he assembled a team of six slender researchers, dubbed “underground astronauts,” who could physically fit through the passage to excavate the fossils. High-resolution laser scanning, photogrammetry, and 3D mapping technology were used to relay images of the excavation to the surface team in near real time, allowing scientists to guide the dig without being physically present in the chamber.1SciELO – Scientific Electronic Library Online. Multimodal spatial mapping and visualisation of Dinaledi Chamber and Rising Star Cave
What emerged was staggering in scale. Over 1,500 fossil specimens were recovered, representing at least 15 individuals of varying ages. That number made Homo naledi one of the largest single-species hominin fossil assemblages ever found in Africa. The bones were embedded in sediment layers within the chamber, with the majority coming from the youngest geological unit, composed of largely unconsolidated material derived from the weathering and erosion of older deposits.1SciELO – Scientific Electronic Library Online. Multimodal spatial mapping and visualisation of Dinaledi Chamber and Rising Star Cave
A Surprisingly Recent Date
When the fossils were first described in 2015, many researchers assumed Homo naledi was millions of years old, given its small brain and numerous primitive skeletal features. The actual dating result upended that expectation. A combination of uranium-series and electron spin resonance dating of three Homo naledi teeth, together with uranium-thorium dating of flowstone layers overlying the fossils, constrained the age of the remains to between 236,000 and 335,000 years ago.2eLife. The age of Homo naledi and associated sediments in the Rising Star Cave, South Africa That places Homo naledi squarely in the Middle Pleistocene, a period when early Homo sapiens were already present in Africa. One study explicitly tested a framework for how these two species could have coexisted during the late Middle Pleistocene in southern Africa, exploring whether they occupied different technological or ecological niches.3Journal of Archaeological Method and Theory. Constraining the Likely Technological Niches of Late Middle Pleistocene Hominins with Homo naledi as Case Study
The dating result matters because it demolished a comfortable assumption: that species with small brains and primitive anatomy are always old. Homo naledi’s survival into the Middle Pleistocene, alongside bigger-brained relatives, suggests the human family tree was far bushier and more complicated than any neat linear progression from ape to human.
A Body Built from Contradictions
If you could see a living Homo naledi, you would notice someone short and slight. Estimates of stature and body mass place it at the low end of the genus Homo, overlapping with larger australopiths and the smallest specimens of Homo erectus from the site of Dmanisi in Georgia. Sexual dimorphism in body mass was modest, less than 20%, which is more like modern humans and Homo erectus than like the earlier australopiths, where males could be considerably larger than females.4PubMed. Body size, brain size, and sexual dimorphism in Homo naledi from the Dinaledi Chamber
The brain was tiny. Two endocranial volume estimates came in at roughly 560 cc and 465 cc, squarely within the range of australopiths and far below the average for Homo erectus or modern humans. Only the smallest Homo habilis specimens, one Homo erectus skull from Dmanisi, and Homo floresiensis overlap with those values.5PubMed Central. Homo naledi, a new species of the genus Homo from the Dinaledi Chamber, South Africa Yet despite that small volume, the surface organization of the brain was not simply a shrunken version of an australopith brain. Several structural features, particularly in the inferior frontal and lateral orbital regions, matched the pattern seen in larger-brained Homo species and were absent in other hominins and great apes.6PubMed Central. Endocast morphology of Homo naledi from the Dinaledi Chamber, South Africa One region of particular interest is the third frontal convolution, which in modern humans contains Broca’s area, a region associated with language and planning. In Homo naledi, this area was expanded relative to brain size to a degree that ranked among the highest values seen in Homo sapiens, Homo erectus, and Neanderthals, and far above chimpanzees and australopiths.7PubMed. The endocast morphology of LES1, Homo naledi
Nobody can say with certainty what an expanded Broca’s area meant for Homo naledi’s cognitive abilities. Brain surface shape alone cannot tell you whether a species could speak or plan. But the finding does complicate the widespread assumption that brain size is the best proxy for behavioral complexity in hominins.
Hands That Climbed and Gripped
The hand is where Homo naledi’s contradictions become vivid. The wrist, thumb, and palm are strikingly human-like. The thumb was long and robust, with well-developed attachment points for the muscles used in forceful, precise gripping, the kind of hand anatomy associated with tool use in Neanderthals and modern humans.8Nature Communications. The hand of Homo naledi But the fingers told a different story. They were long and strongly curved, more so than in most australopiths. The curvature of the finger bones was statistically indistinguishable from that of African apes, and the intermediate finger bones were more curved than in any other known hominin. That degree of curvature is a functional signal: the fingers regularly experienced the heavy loads that come from climbing and hanging from branches.8Nature Communications. The hand of Homo naledi
Internal bone structure confirmed this was not just a leftover ancestral shape that the species had stopped using. Analysis of the cortical bone distribution within the finger bones showed that Homo naledi actively used its hands for both dexterous manipulation and climbing, though the specific climbing strategy differed from that of other hominins like Australopithecus sediba.9PubMed Central. Phalangeal cortical bone distribution reveals different dexterous and climbing behaviors in Australopithecus sediba and Homo naledi
Shoulders for Trees, Feet for the Ground
The upper body was primitive in a way that reinforced the climbing signal from the hands. Homo naledi had a shoulder blade oriented more upward and to the side, sitting high and laterally on the torso rather than low and toward the back as in modern humans. The upper arm bone had extremely low torsion, and the collarbone was australopith-like. Together, these traits suggest a shoulder built for reaching overhead, useful for climbing but lacking the configuration thought to enable effective throwing or running in other early Homo species.10Journal of Human Evolution. The upper limb of Homo naledi
Below the waist, the picture reversed. The foot was predominantly modern human-like, with a big toe aligned with the other toes (not splayed out for grasping), an elongated midfoot, and ankle joints suited for striding bipedalism. The toe bones were more curved than in modern humans, and some researchers initially suggested the arch was flatter, but a subsequent 3D reconstruction found that Homo naledi did have a transverse foot arch, providing biomechanical evidence for stable upright walking.11PubMed Central. The foot of Homo naledi12PubMed. Homo naledi did not have flat foot The lower limb was also elongated relative to body size, another trait shared with Homo erectus and later Homo species rather than with australopiths.4PubMed. Body size, brain size, and sexual dimorphism in Homo naledi from the Dinaledi Chamber
So picture the locomotor repertoire: an animal that walked long distances on two feet over open ground, but that also regularly climbed into trees, perhaps for sleeping, foraging, or shelter. That dual-use body plan was once thought to characterize only very ancient hominins. Finding it in a species that lived alongside early modern humans was a genuine surprise.
What Homo Naledi Ate
Dental microwear analysis, which examines the tiny scratches and pits left on teeth by food, revealed that Homo naledi consumed hard and abrasive foods at least some of the time. The microwear textures were dominated by large, deep pits, suggesting items like nuts or tubers. Among fossil hominins, only the famously hard-object-adapted Paranthropus robustus showed higher average texture complexity, and among living primates, the closest match was the sooty mangabey, a dedicated hard-object feeder.13PubMed. Brief communication: Dental microwear and diet of Homo naledi
Tooth shape and size offered a complementary perspective. Compared to Australopithecus and Paranthropus from the same region, Homo naledi had smaller teeth that were higher-crowned and more resistant to wear. There were no differences in sharpness or complexity of the tooth surface, meaning the foods Homo naledi ate likely had similar fracture properties to those eaten by the older hominins. But the high levels of dental chipping and the wear-resistant tooth design suggest more abrasive particles in the diet, whether from grit-covered roots, dusty environments, or other abrasive food processing.14PubMed. Dental topography and the diet of Homo naledi
How Did the Bones Get There?
The location of the fossils is one of the most debated aspects of the entire discovery. The Dinaledi Chamber is extremely remote within the cave system, reachable only through narrow, winding passages with no direct connection to the surface that would allow large animals to wander in. The taphonomic evidence, meaning the clues about what happened to the bones between death and discovery, systematically rules out the obvious explanations.
There is no evidence that carnivores dragged prey into the chamber: no tooth marks, tooth pits, crenulated bone edges, or splintered shafts of the kind left by predators. No rodent gnawing marks. No stone tool cut marks or chop marks on any of the bones, ruling out butchery by other hominins. None of the bones are burnt. The surrounding sediment shows no signs of water strong enough to transport bones into or within the chamber, and no bones show the rounding, polishing, or pitting that would indicate they were tumbled by flowing water.15eLife. Geological and taphonomic context for the new hominin species Homo naledi from the Dinaledi Chamber, South Africa
With water transport, predator accumulation, and accidental death traps all ruled out, the research team proposed that the bodies were deliberately placed in the chamber by other members of the species, a form of mortuary behavior or body disposal. This is an extraordinary claim for a species with a brain the size of a gorilla’s, and it has been met with serious pushback. A rebuttal paper published in the Journal of Human Evolution argued that there is no scientific evidence that Homo naledi buried its dead or produced rock art, challenging the sufficiency of the evidence and the logic of the inferences.16PubMed Central. No scientific evidence that Homo naledi buried their dead and produced rock art The debate remains unresolved. Even among researchers sympathetic to the idea, the claim is understood as preliminary: suggestive but not proven. The taphonomic evidence is strong on what did not happen to the bones. What did happen remains genuinely uncertain.
Rock Engravings and the Controversy Over Meaning
In addition to the bone deposits, the research team reported finding what appear to be engraved abstract patterns on the dolomitic limestone walls of the Dinaledi Subsystem. The markings include deeply impressed lines, cross-hatchings, percussion marks, and geometric shapes, found on a pillar in the Hill Antechamber and extending into the fissure corridor linking the two chambers.17PubMed 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
Critics have raised two main objections. The first is that the markings might not have been made by hominins at all, perhaps they are natural features of weathered dolomite or scratches from animal claws. The research team countered that dolomite has a Mohs hardness of 3.5 to 4.5, well above the hardness of animal claws (2 to 2.5), and that no other caves in this type of dolomite formation show incised claw markings of comparable depth. No carnivore remains, burrowing activity, droppings, or tooth-marked bones have been found in the subsystem. The second objection is that the engravings could be recent, perhaps made by modern cavers. The team noted that no remains of any hominin other than Homo naledi have been found in the Dinaledi Subsystem, that modern cavers have entered the area only within the last four decades in extremely limited numbers, and that no traces of metallic tools have been detected in association with the markings.18eLife. 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
The engravings remain divisive. If they were genuinely made by Homo naledi, they would represent the oldest known abstract markings by a non-sapiens hominin and would force a rethinking of the relationship between brain size and symbolic behavior. If they were not, the cave still contains one of the largest and most unusual hominin bone assemblages ever found. The scientific value of the site does not hinge on resolving this particular argument.
Where Homo Naledi Fits on the Family Tree
Placing Homo naledi among its relatives has proven difficult, in part because its mosaic anatomy pulls it in different directions depending on which body part you use. Phylogenetic analyses consistently place it within the genus Homo, grouped with other Homo species and Australopithecus sediba, but the exact branching point varies. One study using craniodental data found that Homo antecessor, Asian Homo erectus, Homo habilis, Homo floresiensis, Homo sapiens, and Australopithecus sediba could all plausibly be Homo naledi’s closest relative, an unusual degree of ambiguity.19PubMed. The evolutionary relationships and age of Homo naledi: An assessment using dated Bayesian phylogenetic methods
Skull shape analyses have pointed most often toward Homo erectus as the closest cranial match, though the jaw tells a different story, aligning more with basal Homo and suggesting a potentially deeper divergence.20PubMed. Skull diversity in the Homo lineage and the relative position of Homo naledi A separate analysis based on relative tooth size placed Homo naledi as a sister species to Homo habilis, noting that both share a pattern of tooth proportions that may be ancestral rather than derived.21PubMed. Relative tooth size, Bayesian inference, and Homo naledi
The honest summary is that Homo naledi is firmly a member of Homo but does not slot neatly into any existing branch. It may represent a long-surviving lineage that diverged early from the rest of the genus and retained many primitive features while independently evolving some modern-looking ones. The mosaic makes it resistant to the kind of clean phylogenetic placement that researchers prefer, which is part of what makes it scientifically interesting.
Ancient Diseases in a Small-Brained Hominin
The sheer number of specimens from Dinaledi Chamber has enabled a kind of analysis rarely possible for extinct hominins: paleopathology, the study of ancient disease. One mandible, labeled U.W. 101-1142, preserves an irregular bony growth on the inner surface of the right jaw. Micro-CT scanning revealed the growth to be a peripheral osteoma, a benign bone tumor. It is the first such tumor diagnosis in Homo naledi and one of relatively few benign neoplasms documented in the hominin fossil record.22PubMed. A case of benign osteogenic tumour in Homo naledi: Evidence for peripheral osteoma in the U.W. 101-1142 mandible
Peripheral osteomas are common in living humans and are usually harmless, often going unnoticed unless they interfere with nearby structures. Finding one in Homo naledi does not tell us much about the species’ health in general, but it does remind us that tumors and other growths are not uniquely modern afflictions. They have been part of hominin biology for hundreds of thousands of years, across species with very different brains and bodies. As more of the Dinaledi material is studied, additional pathologies will likely surface, offering a richer view of the physical challenges faced by individuals in this population.
What Makes Homo Naledi So Hard to Categorize
In human evolution, researchers are used to the idea that traits evolve as packages. Big brains come with flat faces. Upright walking comes with shorter arms. Tool-using hands come with reduced climbing ability. Homo naledi violates nearly every one of these expected packages. Its brain was small, but structured in ways associated with complex behavior. Its hands were built for precision grip, but also for hanging from branches. Its feet were made for walking, but its shoulders were made for reaching into trees. Its body mass dimorphism was low, like a modern human, but its brain-to-body ratio was low, like an australopith.
This combination does not fit the traditional ladder-like model of human evolution, where species gain modern traits in a roughly predictable order. Instead, it supports a model in which different body systems evolved semi-independently, at different rates, in response to different pressures. A species could have modern-looking feet and hands alongside a primitive shoulder and brain. The result is not a transitional form in the simple sense of being halfway between australopiths and modern humans. It is something more like a parallel experiment in what a hominin body plan can look like, one that lasted hundreds of thousands of years alongside our own lineage.
Whether Homo naledi left any genetic legacy in living humans is unknown. No ancient DNA has been recovered from the Rising Star fossils, and given the warm, humid conditions of the cave, recovery may never be possible. For now, the species stands as a reminder that the human evolutionary story was not a tidy march from primitive to advanced but a sprawling, overlapping network of populations that each found their own ways to survive.