Estimating the ANB angle of Homo Naledi

Introduction

The Homo Naledi hominin was discovered in the Dinaledi Chamber of the Rising Star cave system in South Africa in 2013. This recent find has created “a stir” among fossil hunters who have named their find Homo naledi. The skull reproduced below has not been age dated as yet, but the recovery team indicates that dating will occur some time in the near future. Speculation has placed the date of this find at possibly less than one million years. It appears that H. Naledi is one of our more recent cousins.

The Site

The cave system is located in the Cradle of Humankind World Heritage Site, Gauteng Province, South Africa a short distance north and west of Johannesburg, Africa. The oro-dental remains include 137 isolated dental specimens and an additional 53 teeth that were found in mandibular or maxillary bone specimens. The researchers have not identified specific primary teeth found at the site...only a reference to their presence. Additional studies of the primary dentition must await further analysis of the dental remains.

See: https://en.wikipedia.org/wiki/Rising_Star_Cave

 

The Rising Star Cave, Figure courtesy of the National Geographic Society

The Rising Star Cave, Figure courtesy of the National Geographic Society

See: http://news.nationalgeographic.com/2015/09/150910-human-evolution-change/

Estimating the ANB angle

At first glance of the full scale rendering of the skull in the October 2015 edition of National Geographic depicts a very prominent mandible with a surprising amount of negative ANB measurement. Present day human cephalograms taken for potential orthodontic treatment often suggest that the angle ANB should have a mean of a plus two degrees in the Caucasian race. The ANB of the above referenced skill was calculated in a non-scientific manner and resulted in a measurement of a minus six degrees, a difference of eight degrees from the Caucasian mean. The vary large discrepancy between Homo sapiens and Homo nalendi is extreme and dramatically demonstrates the prognathic nature of this newly discovered early hominid. (1)

Mandibular Form

An occlusal view of the mandibular shape depicts a parabolic shape with the greatest width at the second molar area. The third molars are positioned somewhat to the lingual, creating an overall ovoid shape. This continuation of the ovoid shape distal to the first molars is unique in relation to present day posterior quadrant morphology. 

The cephalometric points are defined as “A” point, the indentation of the maxilla above the maxillary incisors, “N” or Nasion as the junction of the nasal bone and the maxilla, and “B” point as the indentation just below the apex of the mandibular incisor.

 Homo Naledi

 Homo Naledi

The following quote is taken from the elifesciences.org website referenced below.

“Aside from these limited faunal materials, the Dinaledi collection is entirely composed of hominin skeletal and dental remains. The collection so far comprises 1550 fossil hominin specimens, this number includes 1413 bone specimens and 137 isolated dental specimens; an additional 53 teeth are present in mandibular or maxillary bone specimens. Aside from the fragmentary rodent teeth, all dental crowns (n = 179) are hominin, recovered both from surface collection and excavation. Likewise, aside from the few bird elements, all morphologically informative bone specimens are clearly hominin. In all cases where elements are repeated in the sample, they are morphologically homogeneous, with variation consistent with body size and sex differences within a single population. These remains represent a minimum of 15 hominin individuals, as indicated by the repetition and presence of deciduous and adult dental elements.”

This quotation mentions the presence of primary (deciduous) dental elements but does not directly identify which teeth have been found. The characterization of the permanent teeth is very complete, but any description of primary teeth mentioned within the context of the submission is lacking. So, for now Pediatric Dentists and others will need to rely on a further examination of the recovered skeletal elements to ascertain the character of the primary dentition.

 

Figure 2 

Figure 2 

Illustration “H”in Figure 2 depicts a mandibular form that markedly varies from modern human mandibular shape. The illustration includes the third molars and they are placed somewhat lingual to the mandibular second molars.  Illustration “G” is the basis of the National Geographic composite comparing brain case size of Homo naledi with a modern human skull.

For additional information see: http://dx.doi.org/10.7554/eLife.09560.019

Figure 3  

Figure 3

 

The elongated talonid cuspal morphology of the posterior quadrants illustrates a common feature found on the mandibular bicuspids. This unusual form suggests that masticatory function may be improved when the cuspal form is able to penetrate a tenacious bolus of food. The pointed character of the bicuspids and molars are most visible in “B” of Figure 3.

Primary Teeth Primary (deciduous) teeth were noted in the original article, and any explanation of their number of description is lacking.

For further information on Figure 3 see: http://dx.doi.org/10.7554/eLife.09560.007

Bibliography

Reference 1 http://elifesciences.org/content/4/e09560#sthash.qsRL0ZZe.dpuf accessed September 30, 2015

Reference 2 The Journal of the National Geographic Society, October 2015 See: voices.nationalgeographic.com