A geometric morphometric approach to the study of variation of shovel-shaped incisors

Delphine Carayon (1, 2) , Kaustubh Adhikari (3) , Paul Monsarrat (4) , Jean Dumoncel (1) , José Braga (1, 5) , Benjamin Duployer (6) , Miguel Delgado (7) , Macarena Fuentes-Guajardo (3, 8) , Frikkie de Beer (9) , Jakobus Hoffman (9) , Anna Oettlé (10) , Richard Donat (11, 12) , Lei Pan (13, 14, 15) , Andrés Ruiz-Linares (16, 17, 18) , Christophe Tenailleau (6) , Frédéric Vaysse (1) , Rémi Esclassan (1) , Clément Zanolli (1)

1 AMIS - Anthropologie Moléculaire et Imagerie de Synthèse
2 UM1 - Université Montpellier 1
3 UCL - University College of London [London]
4 STROMALab
5 WITS - University of the Witwatersrand [Johannesburg]
6 CIRIMAT - Centre interuniversitaire de recherche et d'ingenierie des matériaux
7 UPC - Universitat Politècnica de Catalunya = Université polytechnique de Catalogne [Barcelona]
8 Universidad de Tarapaca
9 NECSA - South African Nuclear Energy Corporation [Pretoria]
10 University of Pretoria [South Africa]
11 Inrap - Institut national de recherches archéologiques préventives
12 CAGT - Centre d'anthropologie et de génomique de Toulouse
13 NIGPAS-CAS - Nanjing Institute of Geology and Palaeontology
14 IVPP - Institute of Vertebrate Paleontology and Paleoanthropology
15 State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan
16 UCL-GEE - Dept of Genetics, Evolution and Environment [London]
17 Fudan University [Shanghai]
18 ADES - Anthropologie bio-culturelle, Droit, Ethique et Santé

Objectives : The scoring and analysis of dental nonmetric traits are predominantly accomplished by using the Arizona State University Dental Anthropology System (ASUDAS), a standard protocol based on strict definitions and three‐dimensional dental plaques. However, visual scoring, even when controlled by strict definitions of features, visual reference, and the experience of the observer, includes an unavoidable part of subjectivity. In this methodological contribution, we propose a new quantitative geometric morphometric approach to quickly and efficiently assess the variation of shoveling in modern human maxillary central incisors (UI1). Materials and methods : We analyzed 87 modern human UI1s by means of virtual imaging and the ASU‐UI1 dental plaque grades using geometric morphometrics by placing semilandmarks on the labial crown aspect. The modern human sample was composed of individuals from Europe, Africa, and Asia and included representatives of all seven grades defined by the ASUDAS method. Results : Our results highlighted some limitations in the use of the current UI1 ASUDAS plaque, indicating that it did not necessarily represent an objective gradient of expression of a nonmetric tooth feature. Rating of shoveling tended to be more prone to intra‐ and interobserver bias for the highest grades. In addition, our analyses suggest that the observers were strongly influenced by the depth of the lingual crown aspect when assessing the shoveling. Discussion : In this context, our results provide a reliable and reproducible framework reinforced by statistical results supporting the fact that open scale numerical measurements can complement the ASUDAS method.

Mots clés: Shovel‐shape incisors; Virtual anthropology; Procrustes and non‐Procrustes superimpositions; ASUDAS

Domaines: Anthropologie biologique; Sciences du Vivant [q-bio]

Delphine Carayon, Kaustubh Adhikari, Paul Monsarrat, Jean Dumoncel, José Braga, et al.. A geometric morphometric approach to the study of variation of shovel-shaped incisors. American Journal of Physical Anthropology, 2019, 168 (1), pp.229-241. ⟨10.1002/ajpa.23709⟩. ⟨hal-02296695⟩