Mandibular molar root and pulp cavity morphology in Homo naledi and other Plio-Pleistocene hominins

Kupczik, Kornelius; Delezene, Lucas K.; Skinner, Matthew M.

doi:10.1016/j.jhevol.2019.03.007

Cited by 31 publications

(23 citation statements)

References 44 publications

(61 reference statements)

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“…SK 96 resembles H. naledi in P 3 morphology more closely than any other specimen included here, while Stw 80 falls closest to H. naledi in P 4 shape, and shares the species’ P 3 > P 4 pattern. This would also be consistent with the finding that two key Swartkrans Homo specimens (SK 15 and 45) share a number of molar root characteristics with H. naledi 10 . On the other hand, SKX 21204 also derives from Swartkrans Member 1 (Lower Bank) and is here found to show a number of clear differences in P 3 morphology from SK 96 (see Supplementary Figure 5 a,b).…”

Section: Discussionsupporting

confidence: 89%

“…The similarities between SK 96 and H. naledi could be further evidence 10 for some phylogenetic link between hominins at Swartkrans and H. naledi , while the similarities with Stw 80 may suggest a similar link with Sterkfontein hominins. This is striking given that both Swartkrans Member 1 and Sterkfontein Member 5 West are suggested to predate H. naledi by more than a million years 18 , 24 , 48 – 50 , and would suggest that H. naledi represents a long surviving lineage that split from other members of the genus Homo relatively early.…”

Section: Discussionmentioning

confidence: 87%

“…The permanent postcanine dentition is characterized by small teeth that retain principal molar cusps, but seemingly lack accessory crown traits common in other African hominin groups 1 , 8 . However, the deciduous dentition shows a number of derived Paranthropus -like traits 9 , and molar root metrics find similarities between H. naledi and South African Homo specimens SK 15 and SK 45, as well as KNM-ER 1805 from Koobi Fora 10 .…”

Section: Introductionmentioning

confidence: 95%

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Distinct mandibular premolar crown morphology in Homo naledi and its implications for the evolution of Homo species in southern Africa

Davies

Delezene

Gunz

et al. 2020

Sci Rep

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Homo naledi displays a combination of features across the skeleton not found in any other hominin taxon, which has hindered attempts to determine its placement within the hominin clade. Using geometric morphometrics, we assess the morphology of the mandibular premolars of the species at the enamel-dentine junction (EDJ). Comparing with specimens of Paranthropus, Australopithecus and Homo (n = 97), we find that the H. naledi premolars from the Dinaledi chamber consistently display a suite of traits (e.g., tall crown, well-developed P 3 and p 4 metaconid, strongly developed P 3 mesial marginal ridge, and a P 3 > p 4 size relationship) that distinguish them from known hominin groups. Premolars from a second locality, the Lesedi Chamber, are consistent with this morphology. We also find that two specimens from South Africa, SK 96 (usually attributed to Paranthropus) and Stw 80 (Homo sp.), show similarities to the species, and we discuss a potential evolutionary link between H. naledi and hominins from Sterkfontein and Swartkrans. Homo naledi is a hominin species first described in 2015 based on remains from the Dinaledi Chamber in the Rising Star cave system in South Africa 1 , and subsequently from a second chamber in the cave, the Lesedi Chamber 2. The species presents a combination of features not found in any other taxon, and attempts to interpret its phylogenetic position within the hominin clade have proved difficult. There are remarkably modern features such as the morphology of the foot 3 , as well as the morphology of the wrist and the relative length of the thumb 4. However, the cranial capacity is small, both absolutely and relative to body size 1,2 , and there are primitive Australopithecus-like traits in the fingers 4 , upper and lower limbs 5,6 and pelvis 7. Studies of the dental evidence have likewise revealed a unique combination of features. The permanent postcanine dentition is characterized by small teeth that retain principal molar cusps, but seemingly lack accessory crown traits common in other African hominin groups 1,8. However, the deciduous dentition shows a number of derived Paranthropus-like traits 9 , and molar root metrics find similarities between H. naledi and South African Homo specimens SK 15 and SK 45, as well as KNM-ER 1805 from Koobi Fora 10. Mandibular premolar morphology is particularly useful in studies of hominin taxonomy 11-15 , and initial descriptions suggest the P 3 of H. naledi is highly distinctive. The tooth is absolutely small in size, double rooted, fully bicuspid, and has a symmetrical occlusal outline, a combination of features suggested to be unique among the hominin fossil record 1. Recent morphometric studies of the mandibular premolar enamel-dentine junction (EDJ) demonstrate that this method has the potential to be a powerful tool in distinguishing between hominin taxa 16,17. We therefore aim to further investigate this distinctive premolar morphology at the EDJ.

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Section: Discussionsupporting

confidence: 89%

Section: Discussionmentioning

confidence: 87%

Section: Introductionmentioning

confidence: 95%

See 1 more Smart Citation

Distinct mandibular premolar crown morphology in Homo naledi and its implications for the evolution of Homo species in southern Africa

Davies

Delezene

Gunz

et al. 2020

Sci Rep

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“…As well, the species' molar root metrics revealed similarities with individual specimens of H. habilis (KNM-ER 1805), H. ergaster (SK 15), and early Homo sp. (SK 45) (Kupczik et al, 2019).…”

Section: The Phylogeny Of Homo Naledimentioning

confidence: 99%

Tooth size apportionment, Bayesian inference, and the phylogeny ofHomo naledi

Irish

Grabowski

2020

Preprint

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This study has three main objectives—two methodological and one summative, namely, further characterization of Homo naledi (∼335–236 ka) to more firmly establish its evolutionary history. Using mathematically-corrected mesiodistal and buccolingual crown dimensions, the species was compared with samples of Pan troglodytes, Australopithecus africanus, A. afarensis, Paranthropus robustus, P. boisei, H. habilis, H. ergaster, H. erectus, H. heidelbergensis, H. neanderthalensis, and H. sapiens; the correction yields equivalently scaled samples unaffected by significant interspecific size differences. After initial cluster analysis, the data were used in tooth size apportionment analysis to determine how size is distributed relatively in each species’ dentition, while visualizing this variation in a sample scatterplot. The first main objective then, after quantitative coding, is evaluating the utility of these characters to estimate phylogenetic relationships, here using Bayesian inference with an Mkv model. The second objective, for the first time in paleoanthropological study, is estimating relationships using continuous characters, i.e., the scaled data, through Bayesian inference under a Brownian-motion model. This strategy facilitates maximum reception of potential phylogenetic signal. The final objective based on all analyses, though principally continuous Bayesian inference, is to elucidate the phylogeny of H. naledi. Relationships are largely congruent across methods and, with markedly higher node support, most of those inferred in prior systematic studies using qualitatively discretized traits. The present results place H. naledi as a sister taxon to H. habilis (node support ∼70-99%), with a plesiomorphic pattern of relative tooth size. It is nested within a clade comprising australopiths and early Homo dating 3.3 Ma to ∼800 ka, distinct from younger H. erectus through H. sapiens. This suggests that H. naledi originated well before the geological date range associated with the Dinaledi Chamber, from which the remains in this study were recovered, to represent a long-lived side branch in the genus.

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“…Hominin postcanine tooth root and canal anatomy is highly variable (e.g., Sert and Bayirli, 2004;Prado-Simón et al, 2012a;Kupczik et al, 2019). Using direct observation of the external roots (Turner, 1981;Spencer, 2003;Moggi-Cecchi et al, 2010), 2D radiography (Sperber, 1974;Abbott, 1984;Wood and Engleman, 1988), and medical/micro-tomography (Kupczik et al, 2003(Kupczik et al, , 2005Kupczik and Dean, 2008;Moore et al, 2013Moore et al, , 2015Moore et al, , 2016, studies have demonstrated that tooth roots preserve information about dietary adaptation, taxonomy and phylogeny (Abbott, 1984;Wood and Engleman, 1988;White et al, 2000;Le Cabec et al, 2013;Moore et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Structural analysis of premolar roots in Middle Pleistocene hominins from China

Pan

Dumoncel

Mazurier

et al. 2019

Journal of Human Evolution

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This study investigates permanent maxillary and mandibular premolar root structural organization in East Asian Middle Pleistocene hominins. In addition to analyzing the linear and volumetric properties of the roots, we used a landmark-free approach to both qualify and quantify in 3D premolar root shape variation of Middle Pleistocene hominins in East Asia. Moreover, we focus on some mid-to late East Asian Middle Pleistocene hominin specimens whose taxonomic attribution is unclear. We find considerable cementum in this sample of hominins, similar to other fossil groups, but clearly different from modern humans which have a very small amount of cementum. Additionally, a smaller root pulp cavity is found in later Homo (Neanderthals and modern humans). Our analyses on the crown-root surface area ratio show that East Asian Middle Pleistocene H. erectus as well as one late Middle Pleistocene Homo sp. specimen (PA 81 P 4 from Changyang site) are distinguished from other fossil and extant groups by relatively larger root surface, stout root branches and thick cementum deposits. This may represent a distinct East Asian H. erectus dental pattern. Geometric morphometric analyses on the external root surface reveal a general trend of shape simplification along the Homo lineage examined here, and distinguish Early Pleistocene Homo, Middle Pleistocene H. erectus, Neanderthals and modern human morphologies. The late Middle Pleistocene teeth from Changyang site (PA 76 P 3 and PA 81 P 4) areclose to East Asian H. erectus and Neanderthals, while the mid-Middle Pleistocene P 3 from Panxian Dadong falls within the modern human distribution. Combined with dental crown morphology and root number/form reported in previous studies, our results show that the external root shape canbe considered a taxonomically relevant indicator. In general, an evolutionary tendency towards modern human morphology is observed in part of the East Asian Middle Pleistocene specimens, while a retention of primitive, H. erectus-like features is expressed in some late Middle Pleistocene specimens, supporting a multi-lineage and discontinuous scenario of human settlements in East Asia.

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Mandibular molar root and pulp cavity morphology in Homo naledi and other Plio-Pleistocene hominins

Abstract: The version in the Kent Academic Repository may differ from the final published version. Users are advised to check http://kar.kent.ac.uk for the status of the paper. Users should always cite the published version of record.

Cited by 31 publications

References 44 publications

Distinct mandibular premolar crown morphology in Homo naledi and its implications for the evolution of Homo species in southern Africa

Distinct mandibular premolar crown morphology in Homo naledi and its implications for the evolution of Homo species in southern Africa

Tooth size apportionment, Bayesian inference, and the phylogeny ofHomo naledi

Structural analysis of premolar roots in Middle Pleistocene hominins from China

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