How Science Works - (And Why Religion Doesn't) - Checking and Reassessing the Evidence

Scratch marks on the Rising Star Cave wall. Did Homo naledi really make them?

Homo naledi. A South African hominin with the cranial capacity of a chimpanzee.

No scientific evidence Homo naledi was advanced, News, La Trobe University

The great strength of science is the inbuilt fact-checking mechanism that is an integral part of the scientific method - a method derived from the fact that scientific opinion is always evidence-based and only ever provisional. If new evidence is found or previous evidence is shown to be not what was thought, then scientific opinion changes accordingly.

Religion's great weakness is that it is never evidence-based, so there is nothing to check and reassess. If it was, there would only be one religion and it would be a division of science.

For these reasons, science, for which the facts are a neutral referee, tends to converge on a single explanation, whilst religions tend to diverge and schism into different competing ideologies with no facts to referee the competition and no ultimate winners or truth to converge on, so we end up with about 40,000 Christian sects alone, all claiming to be the one true faith, and condemning the followers of all the others to an eternity of torment.

A case in point, so far as science is concerned, is the recent publication of a reassessment of the evidence behind the claim that the fossil hominin, Homo naledi was a culturally advanced species that made artistic patterns on the cave walls, made fire and buried their dead in prepared graves. The evidence for those claims was that the remains of three individuals were found deep in the cave system, to where it was thought they must have been carried deliberately, and were apparently buried in prepared graves, one with a stone tool close to its hand. There was also what looked like evidence of fire and fire would have been needed to light the way to carry the bodies deep into the cave system.

The finds were something of an enigma because, while having the body of a human, H. naledi had a cranial capacity nearer to that of a chimpanzee, so to have developed a relatively advanced culture with a brain that size would have been surprising. The other surprising thing is that the fossils were dated to around 300,000 years ago, which would have made it contemporaneous with much more advanced hominins such as H. erectus and even early H. sapiens. That was a problem for theories of human evolution that had the savannahs of East and South Africa as the environment in which evolving humans had evolved a large brain, and yet here was H. naledi in the same environment with a brain the size not much larger than that of the hominin-chimpanzee common ancestor.

Tell me all about Homo naledi. Homo naledi is a species of hominin, an extinct member of the human family tree, that was first described in 2015. The fossils were discovered in the Rising Star Cave system near Johannesburg, South Africa. The name "naledi" means "star" in the local Sesotho language. Key points about Homo naledi include:

1. Discovery:The fossils were initially found by recreational cavers Steven Tucker and Rick Hunter in 2013. The excavation, led by paleoanthropologist Lee Berger and his team, recovered more than 1,500 fossil elements from at least 15 individuals.
2. Age:Determining the age of the fossils has been challenging. However, some estimates suggest that Homo naledi lived between 236,000 and 335,000 years ago, during the Middle Pleistocene.
3. Morphology:Homo naledi exhibits a mix of primitive and more modern anatomical features. The species has a small brain size, similar to earlier hominins like Australopithecus, but its hands and feet appear more human-like, suggesting the ability for complex tool use and bipedal locomotion.
4. Body Structure:The overall body structure of Homo naledi is unique. It had a small brain, with an estimated cranial capacity of about 560 to 610 cubic centimeters. The body size is thought to be small, with individuals possibly standing around 4.5 feet (1.4 meters) tall.
5. Cave Burial:One of the most intriguing aspects of the discovery is the suggestion that Homo naledi intentionally disposed of its dead in the remote chambers of the Rising Star Cave system. This behavior, previously thought to be exclusive to more advanced hominins, raises questions about the complexity of Homo naledi's social and cognitive abilities.
6. Implications:The discovery of Homo naledi has significant implications for our understanding of human evolution. It challenges previous notions about the cognitive and behavioral capabilities of more primitive hominins and raises questions about the diversity of hominin species in Africa during the Middle Pleistocene.

The discovery of Homo naledi adds a new layer of complexity to the story of human evolution, prompting further research and investigation into the relationships between different hominin species and the behaviors that shaped our evolutionary history.

The evidence for thinking H. naledi was culturally advanced has now been revisited by a team of anthropologists and paleontologists from La Trobe and Griffiths Universities, Australia, led by Professor María Martinón-Torres, of CENIEH (National Research Center on Human Evolution), Burgos, Spain, and some serious doubts cast on it validity and the conclusions drawn from it. These are the subject of a paper in Journal of Human Evolution. The team also included Diego Garate from the University of Cantabria, Spain. A news release from La Trobe University explains their findings:

The research team conclude the evidence presented so far was not compelling enough to support the deliberate burial of the dead by Homo naledi, nor that they made the purported engravings.

We really need substantial additional documentation and scientific analyses before we can rule out that natural agents and post-depositional processes were responsible for the accumulation of bodies/body parts and to prove the intentional excavation and filling of pits by Homo naledi

Professor Martinón-Torres, lead author
CENIEH (National Research Center on Human Evolution)
Paseo Sierra de Atapuerca, Burgos, Spain.
And Anthropology Department
University College, London, UK

Unfortunately, there is a distinct possibility that the so-called stone artifact next to the hominin hand is a geofact, and not a product of stone tool flaking by Homo naledi.

Professor Michael D. Petraglia, co-author
Australian Research Centre for Human Evolution
Griffith University, Brisbane, Australia

There is no evidence that Homo naledi lit fires in the cave, purported buring [sic] locations could just be from manganese staining and charcoal within the cave remains to be dated. Charcoal from natural fires is not uncommon in caves.

Professor Andy I.R. Herries, co-author
Dept. of Archaeology and History
La Trobe University
Melbourne Campus, Bundoora, VIC, Australia.

Detailed analyses are also needed to demonstrate that the so-called ‘engravings’ are indeed human-made marks, as marks like these can be produced as a product of natural weathering or animal claws.

Diego Garate, co-author.
IIIPC (Instituto Internacional de Investigaciones Prehistóricas de Cantabria)
Universidad de Cantabria, Santander, Spain.

The JHE commentary also offers a brief insight on the state of the field regarding the importance of responsible social communication and the challenges brought by new models of scientific publication.

Professor Herries discussed the Rising Star Cave findings recently on an episode of the Science Versus podcast. Listen to the episode here:

Although this debate has some way to go before a consensus is reached, there is no comfort for creationists in it. There is no suggestion that H. naledi was anything but an archaic hominin showing intermediate features between hominins and a common ancestor with the chimpanzees. The debate is only over the level of cultural development it had reached.

There is also a secondary debate about its place in the hominid family tree. Should it be classified as Homo or Australopithecus? But as with all those other supposedly non-existent intermediate species, it serves to complicate and confuse the picture rather than to clarify it.

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