Another week goes by, another creationist explanation for Homo naledi has been proposed. This latest "hypothesis" - from creation.com - claims it was simply a diseased human (or Homo erectus).
When it was first discovered, Homo naledi was one of the most significant fossils of our ancestors ever. It helped confirm our suspicions about the transition from ape-man to man-ape.
But it's becoming increasingly famous as the bane of creationists. It so thoroughly contradicts their narrative its forcing them to clutch at straws in order to "refute" it.
And in the process it highlights just why creationism is so wrong.
Indecisive creationists
The key flaw in creationism is that it's unscientific. Their ideas are rooted more in belief and motivated reasoning than actual evidence. The disagreement over Homo naledi demonstrates this perfectly.
Creationists' openly admit that their beliefs are what determines their conclusions. They even have statements of faith that spell out exactly what non-evidence based criteria they use to determine the truth. But since the creationist views aren't based on evidence, they can't use evidence to determine who is right. This stops them from being able to evaluate these arguments and arrive at a consensus about what Homo naledi is.
Science can do this. Science does do this. Because it's rooted in examining the evidence we can evaluate the support for a hypothesis and decide if it needs to be thrown out.
But since creationists can't, these mutually contradictory notions keep building up. The Naturalis Historia blog has an excellent post discussing the myriad of different hypotheses proposed by the creationists so far. I pinched the chart below from there, but I would encourage you all to go over and give the original post a read.
Although science might not always arrive at an immediate consensus, at least different ideas (and their evidence) can be discussed. Scientists will debate with each other over the merits of different ideas. Yet creationists aren't evidence based, so can't do this. Answers in Genesis has said nothing about the veracity of the ICR's claims because they can't.
Every new creationist explanation proposed. Every week goes by that they can't arrive at a conclusion. It all serves to reinforce the non-scientific nature of creationism. It shows how they're ideas just aren't evidence based.
Homo naledi: A sickly Homo erectus?
The most recent explanation for Homo naledi was proposed by Dr Line, a neuroscientist from Creation Ministries International. The gist of his argument is that this new species is actually just a member of Homo erectus.
He then proceeds to examine several anatomical features in order to demonstrate the numerous similarities between Homo naledi and Homo erectus. However, he does acknowledge that not every characteristic matches up with Homo erectus. This he attributes to either disease in these fossils, or variation in Homo erectus.
Curiously, the idea that these fossils were Homo erectus was considered by the original authors. Indeed, there's a whole section of the paper where they discuss why Homo naledi doesn't fit in with any known species of hominin. I've quoted their reasoning about why it isn't Homo erectus below, but it is very jargon heavy. Feel free to skip it.
H. naledi lacks the typically distinctive long and low cranial vault of Homo erectus, as well as the metopic keeling that is typically present in the latter species. H. naledi also differs from H. erectus in having a distinct external occipital protuberance in addition to the tuberculum linearum, a laterally inflated mastoid process, a flat and squared nasoalveolar clivus, and an anteriorly shallow palate. The parasagittal keeling that is present between bregma and lambda in H. naledi (DH1 and DH3) is less marked than often occurs in H. erectus, including in small specimens such as KNM-ER 42700 and the Dmanisi cranial sample. Also unlike most specimens of H. erectus, H. naledi has a small vaginal process, a weak crista petrosa, a marked Eustachian process, and a small EAM. The mandible of H. erectus shows a moderately inclined, shelf-like post incisive planum terminating in a variably developed superior transverse torus, differing from the steeply inclined posterior face of the H. naledi mandibular symphysis, which lacks both a post incisive planum or a superior transverse torus. The mental foramen is positioned superiorly and opens posteriorly in DH1, unlike the mid-corpus height, more laterally opening mental foramen of H. erectus. The maxillary and mandibular incisors and canines of H. naledi are smaller than typical of H. erectus. The mandibular P 3 of H. naledi is more molarized and lacks the occlusal simplification seen in H. erectus, they reveal a symmetrical occlusal outline, and multiple roots (2R: MB+D) not typically seen in H. erectus. Furthermore, the molars of H. naledi lack crenulation, secondary fissures, or supernumerary cusps common in H. erectus.
Back with me? Good.
Despite presenting such a plethora of differences with Homo erectus, almost all of these features are ignored by Dr Line. Yes, he does present a range of anatomical similarities between Homo erectus and Homo naledi, but these aren't the characteristics used to define Homo naledi as a separate species. If he wanted to establish they were the same, these were the characteristics he had to "refute".
Instead he focuses on the ribs, hands, feet, and many other attributes. But crucially, none of the attributes that make Homo naledi unique. He's cherry picking the most similar features in order to build his argument, when really he needs to be debating the differences.
For instance, the first anatomical trait Dr Line examines is the ribs (equating human & Neanderthal in this context):
the rib cage does not preclude Homo naledi from also being human, if its rib cage is as suggested by the authors, as it would fall within human variation
If you had the patience (and expertise) to read the previous quote from the paper, you'd realise the authors don't use the ribs to separate Homo naledi and Homo erectus. In other words, this characteristic is completely irrelevant to the discussion yet Dr Line wastes several hundred words on it anyway.
It's the same story when it comes to their hands. The scientists behind Homo naledi note that the hands of Homo erectus aren't that well known, so don't use them to tell the two apart (although they do point out that they fall outside the range of all known humans). But that doesn't stop Dr Line, who grasps at every straw possible in order to make the two seem comparable:
"Mozart's fingers were extremely curved, and that this was possibly due to bone deformities suggestive of old [healed] rickets" . . . Could it be that Homo naledi individuals were, at least in their infancy, prone to suffer from vitamin D deficiency and consequent rickets, from lack of sunlight and low vitamin D content in their diet? This would result in bone abnormality or deformities, as well as growth retardation.
(it's worth noting that rickets also mucks up the long bones, like legs and arms. The limbs of Homo naledi show evidence of no such defmorities. This argument is a complete non starter).
In short, he's cherry picking similarities and completely ignoring the differences.
Dmanisi downfall
Ok, I'm being a bit unfair. Dr Line does directly address one of the key differences between Homo erectus and Homo naledi: the shape of the skull.
Returning to the really long complicated quote, the scientists noted that H. naledi doesn't have the long, low braincase of Homo erectus. This is a pretty major difference, which can't be explained away by Dr Line. Instead he appeals to variation within Homo erectus.
there is indisputable evidence that the morphology of skulls classified by evolutionists as Homo erectus vary considerably . . . Hence, when considering this diversity, and whether Homo naledi belongs with this motley assortment of crania classified as Homo erectus, one could hardly exclude it from membership based on appearance
The evidence for all this variation within the species comes from the Dmanisi fossils. Which to be fair, did show that Homo erectus included a lot of variation. In particular, the recently discovered skull 5 highlighted just how diverse Homo erectus was.
Except that - as the discoverers of skull 5 write - " the braincase [of skull 5] is low but comparatively wide and basally elongate." Even the most variable example of Homo erectus doesn't contain enough variation to explain away the differences with Homo naledi.
tl;dr
This has been a very brief overview of Dr Line's claims. He makes many, many more. Including hinting at the idea this is all a Piltdown man-style fake. I think this posts enough to highlight he's wrong; but if you want to hear more I'll be happy to do a more in-depth follow-up. Just comment below saying so.
Anyhoo, onto the actual conclusion:
Dr Line highlights similarities between Homo naledi and Homo erectus, but ignores the differences. When he does discuss the differences, he's just wrong.
References
Berger, L. R., Hawks, J., de Ruiter, D. J., Churchill, S. E., Schmid, P., Delezene, L. K., ... & Zipfel, B. (2015). Homo naledi, a new species of the genus Homo from the Dinaledi Chamber, South Africa. Elife, 4, e09560.
Lordkipanidze, D., de León, M. S. P., Margvelashvili, A., Rak, Y., Rightmire, G. P., Vekua, A., & Zollikofer, C. P. (2013). A complete skull from Dmanisi, Georgia, and the evolutionary biology of early Homo. Science, 342(6156), 326-331.
