Did Homo naledi Bury its Dead? Four Specialists Challenge Lee Berger's Claims

In June 2023, paleoanthropologist Lee Berger, from the University of the Witwatersrand in Johannesburg, sent shockwaves through the scientific community: according to him, Homo naledi, a homininHomininMember of the subtribe Hominina, comprising the human lineage (Homo, Australopithecus, Paranthropus…) but excluding orangutans and gibbons. The term progressively replaces "hominid" in its narrow sense.→ species discovered in 2013 in the Rising Star Cave and described in 2015, had deliberately buried its dead and produced rock engravings. Published as preprints on the bioRxiv server in June 2023, these claims are now the subject of a critical analysis published in the Journal of Human Evolution by four Spanish, American and South African specialists, who conclude that they lack sufficient scientific foundations.¹

Homo naledi: a species with a surprisingly small brain

Homo naledi is a hominin species discovered in the Dinaledi Chamber within the Rising Star cave system, near Johannesburg, South AfricaAfricaThe cradle of humankind: the continent where the first hominins appeared, then Homo sapiens around 300,000 years ago, before the expansion to the rest of the world.→. Dated between 236,000 and 335,000 years ago, this species displays an unusual morphological combination: a very small brain, comparable to that of Australopithecus, with a volume of approximately 465 to 610 cm3 (compared with an average of 1,350 cm3 for Homo sapiensHomo sapiensThe present-day human species, which emerged in Africa around 300,000 years ago, the only surviving human lineage after the extinction of Neanderthals and Denisovans.→), but a stature and lower limb morphology close to those of modern humans. It was precisely this reduced brain that made Berger's claims so challenging: attributing behaviours as complex as deliberate burialBurialThe intentional deposition of a body, sometimes with offerings; a marker of symbolic behaviour.→ of the dead or the production of art to such a "primitive" hominin meant questioning decades of consensus on the link between cognitive development and symbolic behaviours.

The June 2023 preprints, signed by Berger, John Hawks, Keneiloe Molopyane and other members of the Rising Star team, proposed two distinct claims: first, that the 15 skeletons accumulated in the Dinaledi Chamber had been deliberately placed there by their fellow Homo naledi; and second, that marks observed on the dolomite walls of the cave constituted rock art produced by Homo naledi. These findings received extensive media coverage and became the subject of a National Geographic documentary, even though they had not yet been peer-reviewed at the time of their release.²

An inaccessible cave: the central criticism

The first objection raised by the four authors of the Journal of Human Evolution paper -- Maria Martinon-Torres (CENIEH, Burgos), Diego Garate (Incipit-CSIC), Andy I.R. Herries (La Trobe University) and Michael D. Petraglia (Griffith University) -- concerns the inaccessibility of the Rising Star Cave. The passages leading to the Dinaledi Chamber are exceptionally narrow and dangerous. Berger himself, despite considerable weight loss, emerged badly injured from the cave after his visit. This physical difficulty of access prevented any independent researcher from visiting the site to verify the Rising Star team's observations.

In science, the replicability of observations is a fundamental principle. When the raw data -- here, the fossils and the marks in their geological context -- are only accessible to the team that published the conclusions, it becomes impossible for the community to independently validate or refute those conclusions. The authors note that the Rising Star team did not invite any external specialists in taphonomy, rock art or prehistoric funerary behaviours to assess their observations in the field before disseminating their claims.³

Natural processes were not excluded

The second criticism concerns the failure to demonstrate that the bones could not have accumulated through natural processes. Martinon-Torres and colleagues recall that taphonomy, the discipline studying the processes of accumulation, preservation and transformation of organic remains after death, offers several non-symbolic scenarios to explain concentrations of bones in caves. The Dinaledi Chamber could have constituted a natural death trap, with individuals falling in accidentally. Water transport during flood events, carnivore activity using the cavity as a den, or sedimentary processes could also explain the disposition of the remains.

The basic methodological rule, illustrated by the authors with a striking analogy, is as follows: before advancing an extraordinary explanation, one must first completely refute the ordinary ones. As they put it, if someone claims their house was built by aliens, they must first demonstrate that humans did not build it. Here, according to Martinon-Torres and colleagues, the demonstration that natural scenarios are impossible has not been rigorously completed.⁴

No proof that Homo naledi produced the rock markings

The third criticism, and perhaps the most decisive, concerns the attribution of the wall markings to Homo naledi. Berger and his team identified at three locations on the dolomite walls what they describe as deep cross-hatches and other geometric forms, prepared and smoothed by repeated blows from a heavy object. They attribute these to Homo naledi, the species whose bones were found in the same cave.

Martinon-Torres and colleagues raise two major problems. First, these marks were not dated using direct dating methods. Without precise dating, it is impossible to know whether these traces are contemporary with the occupation by Homo naledi between 236,000 and 335,000 years ago, or whether they were produced at a completely different period, potentially by Homo sapiens or other hominids who may have used the cave at a later time. Second, the mere presence of Homo naledi fossils in the same space does not constitute proof of attribution: two deposits of different nature and age can coexist within the same cavity without any relationship between them. Spatial association does not imply causal association.⁵

Premature dissemination and necessary debate

Beyond the specific scientific arguments, the Homo naledi controversy raises a broader question about contemporary scientific communication practices. Berger's claims were disseminated as preprints not yet peer-reviewed, then immediately amplified by mainstream media and a widely distributed documentary. This inverted timeline, in which media coverage precedes scientific validation, poses a fundamental problem: it removes extraordinary claims from the critical filtering that is the raison d'etre of scientific publication.

The response by Martinon-Torres and colleagues in the Journal of Human Evolution represents precisely the corrective process that the scientific publication system is meant to guarantee. It does not say that Homo naledi did not bury its dead: it says that the evidence presented so far is insufficient to conclude that it did. This is a fundamental distinction. Science advances through the accumulation of evidence and cross-verification, not through proclamation. If future excavations, accessible to independent teams and accompanied by direct dating, enable Berger's claims to be confirmed, they will be accepted. For now, the question remains open.