The much-publicised claim that a species of small-brained ancient human buried its dead and produced rock art is completely unfounded, according to a group of researchers.
“Tłó±đ evidence for burial and rock art is non-existent,” says at Griffith University in Nathan, Australia.
However, the researchers behind the original claim say they are hard at work gathering more evidence to build their case. They also contend that their studies are caught up in a wider debate over how scientific results should be published and critiqued.
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The controversy centres on the extinct hominin Homo naledi, which was first described in 2015 by researchers led by at the University of the Witwatersrand in Johannesburg, South Africa. They had found hundreds of bones in the Rising Star cave system in South Africa, which is difficult to access due to narrow passages.
H. naledi lived around 250,000 years ago. That makes it a contemporary of our species, Homo sapiens, as well as other recent, large-brained hominins like the Neanderthals. However, H. naledi had a small brain typical of much earlier hominins. Despite this, Berger’s team has argued over the years that H. naledi used controlled fire to light its way in the pitch-black caves, and that it placed a child’s skull on an inaccessible ledge – perhaps as part of a funerary rite.
In June, the researchers released initially on the bioRxiv research server, and a few days later in the journal eLife. In these papers and an accompanying , they claimed to have evidence of deliberate burial of corpses in sediments and of engravings carved into cave walls. This was surprising because small-brained hominins like H. naledi weren’t thought to be capable of such symbolic and ritualistic behaviours. Many palaeoanthropologists were publicly sceptical.
“Tłó±đre is a lack of evidence for the interment of a body in an intentional grave pit,” says Petraglia. Instead, the bones could have been naturally accumulated. He and his colleagues have published a paper critiquing Berger’s team’s claims, in which they also argue the purported engravings could be the result of natural erosion processes.
The controversy is partly about the way the research was published. Traditionally, scientific journals send papers to other scientists who supply confidential peer reviews. The journal normally only publishes the studies if the peer reviews are positive. However, eLife is pioneering an alternative model. The journal publishes studies immediately and releases the peer reviews alongside them.
“Tłó±đ eLife review process is totally transparent,” says at the University of Wisconsin-Madison, one of the authors of the June papers. He argues that traditional peer review is open to manipulation because it is confidential.
Negative reviews
In the case of these three papers, the eLife peer reviews were strongly negative. Reviewers described the studies as “incomplete” and “inadequate”, arguing that the evidence wasn’t sufficient to support the claims.
Petraglia wants the team to withdraw the preprints, if possible, and bring in more people. “I would recommend forming a strong, multidisciplinary scientific team composed of geologists, stratigraphers, geochronologists, biological anthropologists who study burial, and rock art experts,” he says. He also wants to see “a strategy for doing proper scientific research”.
Hawks says the team is working to address the reviewers’ concerns, including by supplying additional data and by highlighting previous observations that bolster its case. “I can tell you that having the reviews that we have is going to make final papers that are much stronger and much better,” he says. “That’s the way that the scientific review process is supposed to work. I don’t think there’s anything any different about it here, other than that the public can watch.”
A further complication was that the H. naledi researchers allowed film-makers to follow them as they explored the caves. The result was the Netflix documentary Unknown: Cave of Bones, released in July, which prominently featured the burial and rock art claims. Petraglia argues this was “premature and irresponsible” because the work hadn’t been peer-reviewed.
“People should be aware that scientists do not have editorial control over documentaries,” says Hawks. He argues it is all part of their attempts to be transparent. “In this case, we were able to allow cameras and journalists to be present in our work. And it happens that we made some interesting discoveries.”
Hawks and his colleagues were invited to submit a response to Petraglia’s paper, but only once it was peer-reviewed and about to be published. They have drafted their response, but it hasn’t yet been peer-reviewed, so the journal asked them not to share it with żěè¶ĚĘÓƵ.
Journal of Human Evolution
