The Skull of Homo Naledi

Adapted from Is It Human? Assessing the Homo naledi Debate, available here.

Wikipedia reported “Four skulls were discovered, thought to be two female and two males…”¹⁾Wikipedia, Homo naledi; https://en.wikipedia.org/wiki/Homo_naledi The formal description by Berger et al. clarifies, “The endocranial volume of all H. naledi specimens is clearly small compared to most known examples of Homo…. Despite its small vault size, the cranium of H. naledi is structurally similar to those of early Homo.”²⁾Lee Berger, et al., “Homo naledi, a new species of the genus Homo from the Dinaledi Chamber, South Africa,” Sep 10, 2015, http://elifesciences.org/content/4/e09560.full

This stands in stark contrast to the interpretation offered by Richard Dawkins, who emphasized the small cranial size as a significant impediment to classifying the species within the genus Homo. Yet Dawkins ultimately concedes that cranial capacity should no longer be viewed as the defining criterion for genus classification³⁾See Dawkin’s quote in Heath Henning, Homo Naledi: The Rising Star of Evolutionary Icons, p. 41 Dawkins’ conclusion appears to follow the trajectory laid out by Berger and colleagues, who assert that structural similarities outweigh the discrepancy in brain size.

A revealing statement from National Geographic notes, “In their general morphology they clearly looked advanced enough to be called Homo. But the braincases were tiny—a mere 560 cubic centimeters for the males and 465 for the females… These were not human beings. These were pinheads, with some human like parts.”⁴⁾Jamie Shreeve, “This Face Changes the Human Story. But How?” Sep. 10, 2015, National Geographic; http://news.nationalgeographic.com/2015/09/150910-human-evolution-change/ The claim of “some humanlike parts” is dubious unless the term “like” is applied with significant latitude. Nevertheless, the statement accurately underscores the critical issue—the diminutive cranial volume. If these specimens are not to be considered fully human, on what grounds are they still classified within the Homo genus?

The reported cranial capacity of H. naledi—ranging from 465 to 560 cubic centimeters—is well within the range of great apes such as orangutans and chimpanzees, while significantly below that of modern humans, which typically range between 1,100 and 1,700 cc. This discrepancy is a crucial consideration in determining phylogenetic relationships.

Since there are variations in tissues and fluids, the cranial capacity is never exactly equal to brain size, but can give an approximation. A skull’s capacity is determined by pouring seeds or buckshot into the large hole at the base of the skull (foramen magnum), then emptying the pellets in to a measuring jar. The volume is usually given in cubic centimeters (cc.). Living humans have a cranial capacity ranging from about 950cc. to 1,800cc., with the average about 1,400cc.⁵⁾Richard Milner, The Encyclopedia of Evolution: Humanity’s Search for Its Origin, Henry Holt and Company, 1993, p. 98

Sci-News quoted Professor Paul Dirks as stating:

“The features of Homo naledi are similar to other early hominids combining a human-like face, feet and hands, but with a short, ape-like torso and a very small brain,” said Prof. Paul Dirks of James Cook University.⁶⁾“Homo  naledi: New Species of Human Ancestor Dicovered” Sep. 10, 2015, Sci-News; http://www.sci-news.com/othersciences/anthropology/science-homo-naledi-03224.html

However, visual evidence and published data do not fully substantiate Dirks’ summary. Dr. Elizabeth Mitchell offered a more cautious appraisal: “Nevertheless, despite a sloped lower face and—based on the published photographs—no vissible evidence of the protruding nasal bones typical of all humans, Berger has identified the fossils as a new species of human ancestor, Homo naledi.”⁷⁾Dr. Elizebeth Mitchell, “Is Homo naledi a New Species of Human Ancestor?” Sep. 12, 2015, https://answersingenesis.org/human-evolution/homo-naledi-new-species-human-ancestor/ Dr. Mitchell’s observation is echoed in the anatomical analysis of Dr. David Menton:

The human skull is easily distinguished from all living apes, though there are, of course, similarities. The vault of the skull is large in humans because of their relatively large brain compared to apes. From this perspective, the face of the human is nearly vertical, while that of the ape slopes forward from its upper face to its chin.  From a side view, the bony socket of the eye (the orbit) of an ape is obscured by its broad, flat upper face.  Humans, on the other hand, have a more curved upper face and forehead, clearly revealing the orbit of the eye from a side view.  Another distinctive feature of the human skull is the nose bone that our glasses rest on. Apes do not have protruding nasal bones and would have great difficulty wearing glasses.⁸⁾Dr. David Menton, “Did Humans Really Evolve from Apelike Creatures?” http://www.answersingenesis.org/articles/nab2/humans-evolve-apelike-creatures

This anatomical context highlights significant disjunctions between H. naledi and modern humans, particularly in cranial morphology. The decision to classify these remains within the genus Homo appears more ideological than empirical, driven by a narrative that increasingly tolerates broad morphological variability under the human lineage umbrella.

The image below, presented by National Geographic, offers a visual comparison between the Homo naledi skull and that of an average modern human. According to the article, the H. naledi skull depicted is the largest specimen recovered, with a cranial capacity of 560 cubic centimeters. However, National Geographic provides no indication of the comparative scale used for the human skull that appears as a shadowed outline behind it. This omission raises a pertinent question: did the editors select the smallest reasonable human skull or the largest to minimize the stark visual disparity in cranial size?

[Image retrieved from nationalgeographic.com⁹⁾Jamie Shreeve, “This Face Changes the Human Story. But How?” Sep. 10, 2015, National Geographic; http://news.nationalgeographic.com/2015/09/150910-human-evolution-change/]

Critically analyzing the image, one notices that only the skull cap and jaw of H. naledi are illustrated, and these are superimposed within the silhouette of a human skull in the background. This presentation immediately raises concerns about representational fairness.

First, consider the slope from the crown of the skull to the brow ridge: in modern humans, this angle is relatively vertical, while in H. naledi, the slope is much more pronounced. The visual presentation downplays this distinction.

Next, observe how the slope from the base of the human skull has been approximated in nearly identical fashion to that of H. naledi. This visual continuity suggests a reconstructed lower skull structure for H. naledi that may not be justified by the actual fossil evidence. The composite may thus misrepresent the anatomical reality by inferring continuity where none is preserved.

Finally, if one follows a consistent angular trajectory extrapolated from the preserved jaw and frontal bones of H. naledi, the rear vault of the skull should project further backward than it does in the image. This would result in a more sloped and elongated cranial shape—closer to that observed in extant great apes than in modern humans.

If we follow these angles, we find that the skull and jaw align in a manner consistent with a sloping facial structure, as illustrated here.

Such cranial angles are more consistent with the morphology of a chimpanzee skull.

[Image retrieved from D. Roberts, Photo Researchers Inc.¹⁰⁾http://chronicle.com/article/How-Our-Brains-Got-BigOur/128878/]

In this comparative image, one observes the significant slope of the chimpanzee face, the absence of a nasal bone, and the considerable difference in overall size. As noted: “The human skull (left) houses a brain that’s three to four times the size of a chimpanzee’s (right). Scientists have spotted a stretch of DNA that could have prompted this expansion.”¹¹⁾Josh Fischman, How Our Brains got Big…” September  4, 2011; http://chronicle.com/article/How-Our-Brains-Got-BigOur/128878/

When the fragments of the Homo naledi skull are overlaid onto the chimpanzee skull, with the angles preserved as illustrated in the earlier image, the resulting alignment is striking. The cranial trajectory, sloped face, and proportions correspond far more closely with the chimpanzee than with the modern human.

The discovery of the Neo skull from the Lesedi Chamber provides an important opportunity to evaluate whether the cranial and facial angles previously inferred from Homo naledi remains are accurately represented in published imagery. Frequently, the Neo skull is presented in direct visual comparison with that of a modern human. John Hawks presents an image of the Neo skull alongside a visual comparison with that of an archaic human specimen.

[Image retrieved from John Hawks, “South African cave yeields yet more fossils of a newfound relative,” May 9, 2017; https://news.wisc.edu/south-african-cave-yields-yet-more-fossils-of-a-newfound-relative/]

However, the MorphoSource image of the Neo specimen portrays a noticeably sloped facial profile.

When this MorphoSource image is analyzed in relation to the expected anatomical angles—particularly when aligning the jaw and cranial vault—it proves to be a relatively accurate representation. In contrast, more commonly circulated images of the Neo skull appear to minimize this sloping characteristic.

A direct comparison between the predicted cranial angles (based on jaw and skull cap alignment) and the more frequently presented Neo image suggests that the latter may be intentionally tilted to give the illusion of a flatter, more human-like face.

In the following image, a red arrow has been placed to indicate the angle that would be expected; however, it is evident that the Neo skull has been tilted to produce the appearance of a flatter face. Additionally, observe the dentition closely in these images. Notably, in the commonly circulated image of Neo (on the right), the teeth are angled upward—an orientation that does not reflect the natural alignment of dentition, nor does it correspond to what is observed in the Morphosource 3D reconstruction of the skull.

To provide a clearer visualization of the dental misalignment, the two skull fragments were juxtaposed to emphasize the discrepancy in the alignment of the jaw.

However, when the Neo skull is repositioned to align its teeth with the mandible (DH1), the sloped profile becomes more apparent, better corresponding to the anatomical structure observed in apes.

A recurring issue in paleoanthropology, especially with so-called evolutionary “icons,” is the conspicuous absence of the very portions of the skull that would decisively clarify the anatomical identity of the specimen. As Bonnie Yoshida explains in her online lecture Early Hominin Evolution:

Early Hominin Evolution” says, “The face and jaws of humans lie underneath the brain case rather than protruding out like the ape. If you look at a profile-view of the human skull…the lower face hardly projects at all. A protruding lower face or snout-like appearance… is called prognathism. A gradual reduction in prognathism is a trend through time in the hominin lineage.¹²⁾Bonnie Yoshida, “Early Hominin Evolution,” Last Updated 01/13/2015; http://gctest,grossmont.edu/people/bonnie-yoshida-levine/online-lectures/early-hominin-ev.aspex

Had Berger’s team recovered the missing facial bones of Homo naledi, it is unlikely they could have plausibly maintained its status as an intermediate form between Australopithecus sediba and Homo sapiens.

A historical parallel can be drawn with the controversial case of Java Man. Discovered by Dutch anthropologist Eugène Dubois (1858–1940), Java Man was initially classified as an intermediate species despite having only partial cranial remains. While some critics—including certain creationist commentators—misunderstood Dubois to have equated the fossil with a giant gibbon, mainstream evolutionary scientists today classify Java Man within Homo erectus. However, evidence such as H. erectus‘s seafaring capabilities and distribution across the Indonesian islands of Lombok, Bali, Sumbawa, and Flores strongly suggests that it was fully human.¹³⁾Jonathan Sarfati, PH.D., F.M., The Greatest Hoax on Earth? Refuting Dawkins on Evolution, Creation Book Publishers (Atlanta, Georgia: 2010), p. 161

With earlier fossil discoveries, the fragmentary nature of remains often made reconstruction speculative at best. In the case of Homo naledi, however, a large number of bones were recovered—yet ambiguity remains. This is in part due to the reconstruction process, which often fills gaps with artistically or ideologically driven assumptions.

For example, the Berger et al. paper includes an illustration in which blue-shaded regions represent computer-generated reconstructions. These reconstructions match the more human-like skull shape presented in National Geographic, but they conspicuously lack the pronounced prognathism (facial slope) expected from the actual fossil evidence.

Interestingly, embedded within the technical language of the same Berger et al. paper is an admission that the face of Homo naledi differs from that of Homo erectus specifically because of its more sloped facial plane:

“differing from the steeply inclined posterior face of H. naledi…”¹⁴⁾Lee Berger, et al., “Homo naledi, a new species of the genus Homo from the Dinaledi Chamber, South Africa,” Sep 10, 2015, http://elifesciences.org/content/4/e09560.full which depicts a sloping face we would expect but are not being shown in the artistic renditions.

[Image retrieved from Lee Berger et. al paper, elifescience.org¹⁵⁾Lee Berger, et al., “Homo naledi, a new species of the genus Homo from the Dinaledi Chamber, South Africa,” Sep 10, 2015, http://elifesciences.org/content/4/e09560.full]