Homo naledi is an extinct species of archaic human discovered in 2013 in the Rising Star Cave system, Gauteng province, South Africa, part of the Cradle of Humankind, dating back to the Middle Pleistocene 335,000–236,000 years ago. The excavation comprises 1,550 specimens of bone, representing 737 different skeletal elements, and at least 15 different individuals. Despite this exceptionally high number of specimens, their classification with other Homo species remains unclear.
Along with similarities to contemporary Homo, they share several characteristics with the ancestral Australopithecus as well as early Homo (mosaic evolution), most notably a small cranial capacity of 465–610 cm3 (28.4–37.2 cu in), compared with 1,270–1,330 cm3 (78–81 cu in) in modern humans. They are estimated to have averaged in height and in weight, yielding a small relative brain size, encephalization quotient, of 4.5. H. naledi brain anatomy seems to have been similar to contemporary Homo, which could indicate comparable cognitive complexity. The persistence of small-brained humans for so long in the midst of bigger-brained contemporaries revises the previous conception that a larger brain would necessarily lead to an evolutionary advantage, and their mosaic anatomy greatly expands the known range of variation for the genus.
H. naledi anatomy indicates that, although they were capable of long-distance travel with a humanlike stride and gait, they were more arboreal than other Homo, better adapted to climbing and suspensory behaviour in trees than endurance running. Tooth anatomy suggests consumption of gritty foods covered in particulates such as dust or dirt, suggesting a diet of nuts and tubers.
Although they have not been associated with stone tools or any indication of material culture, they appear to have been dexterous enough to produce and handle tools. Therefore, they may have manufactured Early or Middle Stone Age industries found in excavations near their fossils, since no other human species in the vicinity at that time has been discovered. It has also been controversially postulated that these individuals were buried deliberately by being carried into and placed in the chamber. Some researchers suggest that H. naledi also may have carved crosshatched rock signs in a passage to what could be a burial chamber, but many paleontologists question this hypothesis.
Discovery
On 13 September 2013 while exploring the Rising Star Cave system in the Cradle of Humankind, South Africa, cavers Rick Hunter and Steven Tucker found hominin fossils at the bottom of the Dinaledi Chamber. On 24 September, they returned to the chamber and took photographs that they showed to South African palaeoanthropologists Pedro Boshoff and Lee Rogers Berger on 1 October. Berger assembled an excavation team that included Hunter and Tucker, and six women selected for their slender build, the so-called "Underground Astronauts".
The chamber had been entered at least once before, by cavers in the early 1990s. They rearranged some bones and may have caused further damage, although much of the floor in the chamber had not been walked on prior to 2013. The site lies about from the main entrance, at the bottom of a vertical drop, and the long main passage is only at its narrowest. In total, more than 1,550 pieces of bone belonging to at least fifteen individuals (9 immature and 6 adults) have been recovered from the clay-rich sediments. Berger and colleagues published the findings in 2015.
The fossils represent 737 anatomical elements – including portions of the skull, jaw, ribs, teeth, limbs, and inner ear bones – from old, adult, young, and infantile individuals. There are also some articulated or near-articulated elements, including the skull with the jaw bone, and nearly complete hands and feet. With the number of individuals of both genders across several age demographics, it then became the richest assemblage of associated fossil hominins discovered in Africa. Aside from the Sima de los Huesos collection and later Neanderthal and modern human samples, the excavation site has the most comprehensive representation of skeletal elements across the lifespan, and from multiple individuals, in the hominin fossil record by that time.
The holotype specimen, DH1, comprises a partial calvaria (top of the skull), partial maxilla, and nearly complete jawbone. The paratypes, DH2 through DH5, all comprise partial calvaria. Because the remains came from Rising Star Cave, in 2015, Berger and colleagues named the species Homo naledi with the specific name meaning "star" in the Sotho language.
The remains of at least three additional individuals (two adults and a child) were reported in the Lesedi Chamber of the cave by John Hawks and colleagues in 2017. In 2026, proteomic analysis of tooth enamel found no evidence of male markers in the studied sample representing at least 20 individuals.
Classification In 2017, the Dinaledi remains were dated to 335,000–236,000 years ago in the Middle Pleistocene, using electron spin resonance (ESR) and uranium–thorium (U-Th) dating on three teeth, and U-Th and paleomagnetic dating of the sediments they were deposited in. Previously, the fossils were thought to have dated to 1–2 million years ago, because no similarly small-brained hominins had been known from such a recent date in Africa. The smaller-brained Homo floresiensis of Indonesia lived on an isolated island and, apparently, became extinct shortly after the arrival of modern humans.
The ability of such a small-brained hominin to have survived for so long in the midst of bigger-brained Homo has greatly revised previous conceptions of human evolution and the notion that a larger brain would necessarily lead to an evolutionary advantage. Their mosaic anatomy also greatly expands the range of variation for the genus.
H. naledi is hypothesised to have branched off very early from contemporaneous Homo. It is unclear whether they branched off at approximately the time of H. habilis, H. rudolfensis, and A. sediba, are a sister taxon to H. erectus and the contemporaneous large-brained Homo, or are a sister taxon to the descendants of H. heidelbergensis (modern humans and Neanderthals). This places the branching from contemporary Homo in a range of time from as early as the Pliocene to 900,000 years ago at the latest. It is also possible that their ancestors speciated after an interbreeding event between Homo and late australopithecines. Comparison of skull features reveals that H. naledi has the closest affinities to H. erectus.
It is unclear whether these H. naledi were an isolated population in the Cradle of Humankind, or were ranged across Africa. If the latter, then several gracile hominin fossils from African sites that traditionally have been classified as late H. erectus might instead represent H. naledi specimens.
Although earlier study placed H. naledi as a late offshoot from H. erectus in the phylogenetic tree,Dembo M, Radovčić D, Garvin HM, Laird MF, Schroeder L, Scott JE, et al. (August 2016). "The evolutionary relationships and age of Homo naledi: An assessment using dated Bayesian phylogenetic methods". Journal of Human Evolution. 97: 17–26. Bibcode:2016JHumE..97...17D. doi:10.1016/j.jhevol.2016.04.008. hdl:2164/8796. PMID 27457542. the recent study places H. naledi as an early offshoot from H. erectus in the phylogenetic tree.
Anatomy Skull
Two H. naledi skulls from the Dinaledi chamber had cranial volumes of approximately , and two female skulls . A H. naledi skull from the Lesedi chamber had a cranial volume of . The Dinaledi specimens are more similar to the cranial capacity of australopithecines. For comparison, H. erectus averaged approximately , and modern humans for males and females respectively. The Lesedi specimen is more within the range of H. habilis and H. e. georgicus. The encephalization quotient of H. naledi was estimated at 3.75, which is the same as the pygmy H. floresiensis, but notably smaller than all other Homo. Contemporary Homo were all above 6, H. e. georgicus at 3.55, and A. africanus at 3.81. It is unclear whether H. naledi inherited small brain size from the last common Homo ancestor, or whether it was evolved secondarily and more recently.
The skull morphology is more similar to Homo, with a slenderer shape, the asymmetry in both the temporal and occipital lobes of the brain, and reduced post-orbital constriction, with the skull not becoming narrower behind the eye-sockets. The frontal lobe morphology is more or less the same in all Homo brains despite size, and differs from Australopithecus, a characteristic that has been implicated in the production of tools, the development of language, and sociality.
Similarly to modern humans (but not to fossil hominins, including South African australopithecines, H. erectus, and Neanderthals) the permanent second molar of H. naledi erupted comparatively late in life, emerging alongside the premolars instead of before, a characteristic that indicates a slower maturation unusually comparable to modern humans. The tooth formation rate of the front teeth is also most similar to modern humans. The overall size and shape of the molars most closely resemble those of three unidentified Homo specimens from the local Swartkrans and East African Koobi Fora Caves, and are similar in size (but not shape) to Pleistocene H. sapiens. The necks of the molars are proportionally similar to those of A. afarensis and Paranthropus.
Unlike modern humans and contemporary Homo, H. naledi lacks several accessory dental features, and has a high frequency of individuals who present main cusps, namely the metacone (midline on the tongue-side) and hypocone (to the right on the lip-side) on the second and third molars, and a Y-shaped hypoconulid (a ridge on the lip-side toward the cheek) on all three molars. The premolars of H. naledi are characterised by a well-developed P3 and P4 metaconid, strongly developed P3 mesial marginal ridge, a larger P3 than P4, and tall crowns, distinguishing them from the premolars of other Homo species. Nonetheless, H. naledi also has many dental similarities with contemporary Homo.
The anvil (a middle ear bone) more resembles those of chimps, gorillas, and Paranthropus than Homo. Like H. habilis and H. erectus, H. naledi has a well-developed brow-ridge with a fissure stretching across just above the ridge and, like H. erectus, a pronounced occipital bun. H. naledi has some facial similarities with H. rudolfensis.
Build
The H. naledi specimens are estimated to have, on average, stood approximately and weighed . This body mass is intermediate between what is typically seen in Australopithecus and Homo species. Like other Homo, female and male H. naledi were likely about the same size. A juvenile specimen, DH7, is skeletally consistent with a growth rate similar to the faster ape-like trajectories of MH1 (A. sediba) and Turkana boy (H. ergaster). Because dental development is so similar to that of modern humans, a slower maturation rate is not completely out of the question. Using the faster growth rate, DH7 would have died at 8–11 years old, but using the slower growth, DH7 would have died at 11–15 years old.