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Link to original content: http://pubmed.ncbi.nlm.nih.gov/30383758/
Disentangling isolated dental remains of Asian Pleistocene hominins and pongines - PubMed Skip to main page content
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. 2018 Nov 1;13(11):e0204737.
doi: 10.1371/journal.pone.0204737. eCollection 2018.

Disentangling isolated dental remains of Asian Pleistocene hominins and pongines

Tanya M Smith  1   2 , Alexandra Houssaye  2   3   4 , Ottmar Kullmer  5   6 , Adeline Le Cabec  2   3   7 , Anthony J Olejniczak  8 , Friedemann Schrenk  5   6 , John de Vos  9 , Paul Tafforeau  3
Affiliations

Disentangling isolated dental remains of Asian Pleistocene hominins and pongines

Tanya M Smith et al. PLoS One. .

Abstract

Scholars have debated the taxonomic identity of isolated primate teeth from the Asian Pleistocene for over a century, which is complicated by morphological and metric convergence between orangutan (Pongo) and hominin (Homo) molariform teeth. Like Homo erectus, Pongo once showed considerable dental variation and a wide distribution throughout mainland and insular Asia. In order to clarify the utility of isolated dental remains to document the presence of hominins during Asian prehistory, we examined enamel thickness, enamel-dentine junction shape, and crown development in 33 molars from G. H. R. von Koenigswald's Chinese Apothecary collection (11 Sinanthropus officinalis [= Homo erectus], 21 "Hemanthropus peii," and 1 "Hemanthropus peii" or Pongo) and 7 molars from Sangiran dome (either Homo erectus or Pongo). All fossil teeth were imaged with non-destructive conventional and/or synchrotron micro-computed tomography. These were compared to H. erectus teeth from Zhoukoudian, Sangiran and Trinil, and a large comparative sample of fossil Pongo, recent Pongo, and recent human teeth. We find that Homo and Pongo molars overlap substantially in relative enamel thickness; molar enamel-dentine junction shape is more distinctive, with Pongo showing relatively shorter dentine horns and wider crowns than Homo. Long-period line periodicity values are significantly greater in Pongo than in H. erectus, leading to longer crown formation times in the former. Most of the sample originally assigned to S. officinalis and H. erectus shows greater affinity to Pongo than to the hominin comparative sample. Moreover, enamel thickness, enamel-dentine junction shape, and a long-period line periodicity value in the "Hemanthropus peii" sample are indistinguishable from fossil Pongo. These results underscore the need for additional recovery and study of associated dentitions prior to erecting new taxa from isolated teeth.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Homo erectus upper molar (Trinil 11620) tracing showing measurements for enamel thickness and enamel-dentine junction morphology characterization.
The area of the enamel cap is represented as c, the area of the dentine under the enamel cap is represented as b, and the length of the enamel-dentine junction is represented as e. Landmarks are defined as follows: 1) tip of the lingual enamel cervix; 2) lingual intersection of the EDJ and a line parallel to the cervical diameter and bisecting the length between the cervical diameter and landmark 5; 3) lingual intersection of the EDJ and a line parallel to the cervical diameter and running through landmark 5; 4) mesiolingual dentine horn tip; 5) lowest point of the EDJ between the mesiolingual and mesiobuccal cusp tips; 6) mesiobuccal dentine horn tip; 7) buccal intersection of the EDJ and a line parallel to the cervical diameter and running through landmark 5; 8) buccal intersection of the EDJ and a line parallel to the cervical diameter and bisecting the length between the cervical diameter and landmark 5; and, 9) tip of the buccal enamel cervix. Landmark 1 was made to lie at x, y coordinate (0, 0) and landmark 9 at (0, 100) in every specimen examined in order to account for differences in tooth size. Reproduced from [30].
Fig 2
Fig 2. Virtual histological slice showing long-period line periodicity.
Ten daily cross-striations can be seen (light and dark bands in white brackets) between long-period lines (arrows) in CA 808. The scale bar is equal to 100 μm.
Fig 3
Fig 3. Two-dimensional relative enamel thickness values for maxillary (upper plot) and mandibular (lower plot) molars in the study sample (ungrouped cases) and comparative material.
Standard box and whisker plot revealing the interquartile range (25th–75th percentiles: bars), 1.5 interquartile ranges (whiskers), and the median values (black line). Outliers are signified by circles. There are no data available regarding enamel thickness for mandibular molars of H. erectus.
Fig 4
Fig 4. Plot depicting scores on the first two discriminant functions resulting from the DFA of maxillary (upper plot) and mandibular (lower plot) molar enamel-dentine junction shape metrics, and the position of the study sample.
Note that there are no data available regarding enamel-dentine junction shape for mandibular molars of H. erectus.
Fig 5
Fig 5. Plot depicting scores on the first two discriminant functions resulting from the DFA of maxillary (upper plot) and mandibular (lower plot) molar enamel-dentine junction shape metrics and position of 19 "Hemanthropus peii" molars.
Fig 6
Fig 6. Crown formation times (days) in molar mesial cusps.
UM = upper molar, LM = lower molar, mb = mesiobuccal cusp, ml = mesiolingual cusp. Note that first, second, and third molars have been combined for each cusp position due to uncertainty of the serial position of some fossil molars. Multiple estimates are presented for fossil samples with uncertain periodicity values (CA 796, CA 804, S7-65). H. erectus data (S7-37): [71]; H. sapiens: [72]; extant and fossil Pongo: [54] and this study.
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Grants and funding

This research was supported by the European Synchrotron Radiation Facility, Griffith University, Harvard University, Max Planck Society, Senckenberg Gesellschaft für Naturforschung, and NSF grant BCS 1126470. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.