A radiographic study of permanent molar development in wild Virunga mountain gorillas of known chronological age from Rwanda

Alexandra E. Kralick, M. Loring Burgess, Halszka Glowacka, Keely Arbenz-Smith, Kate Mcgrath, Christopher B Ruff, King Chong Chan, Michael R. Cranfield, Tara S. Stoinski, Timothy G. Bromage, Antoine Mudakikwa, Shannon C. Mcfarlin

Research output: Contribution to journalArticle

Abstract

Objectives: While dental development is important to life history investigations, data from wild known-aged great apes are scarce. We report on the first radiographic examination of dental development in wild Virunga mountain gorillas, using known-age skeletal samples recovered in Rwanda. Materials and methods: In 43 individuals (0.0-14.94 years), we collected radiographs of mandibular molars, and where possible, cone beam CT scans. Molar crown and root calcification status was assessed using two established staging systems, and age prediction equations generated using polynomial regression. Results were compared to available data from known-age captive and wild chimpanzees. Results: Mountain gorillas generally fell within reported captive chimpanzee distributions or exceeded them, exhibiting older ages at equivalent radiographic stages of development. Differences reflect delayed initiation and/or an extended duration of second molar crown development, and extended first and second molar root development, in mountain gorillas compared to captive chimpanzees. However, differences in the duration of molar root development were less evident compared to wild chimpanzees. Discussion: Despite sample limitations, our findings extend the known range of variation in radiographic estimates of molar formation timing in great apes, and provide a new age prediction technique based on wild specimens. However, mountain gorillas do not appear accelerated in radiographic assessment of molar formation compared to chimpanzees, as they are for other life history traits. Future studies should aim to resolve the influence of species differences, wild versus captive environments, and/or sampling phenomena on patterns observed here, and more generally, how they relate to variation in tooth size, eruption timing, and developmental life history.

Original languageEnglish (US)
JournalAmerican Journal of Physical Anthropology
DOIs
StateAccepted/In press - 2017

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Rwanda
Gorilla gorilla
Pan troglodytes
Hominidae
Crowns
Tooth
Tooth Eruption
Cone-Beam Computed Tomography
New Age
staging
regression
examination

Keywords

  • Dental development
  • Gorilla beringei beringei
  • Radiographs

ASJC Scopus subject areas

  • Anatomy
  • Anthropology

Cite this

A radiographic study of permanent molar development in wild Virunga mountain gorillas of known chronological age from Rwanda. / Kralick, Alexandra E.; Loring Burgess, M.; Glowacka, Halszka; Arbenz-Smith, Keely; Mcgrath, Kate; Ruff, Christopher B; Chan, King Chong; Cranfield, Michael R.; Stoinski, Tara S.; Bromage, Timothy G.; Mudakikwa, Antoine; Mcfarlin, Shannon C.

In: American Journal of Physical Anthropology, 2017.

Research output: Contribution to journalArticle

Kralick, AE, Loring Burgess, M, Glowacka, H, Arbenz-Smith, K, Mcgrath, K, Ruff, CB, Chan, KC, Cranfield, MR, Stoinski, TS, Bromage, TG, Mudakikwa, A & Mcfarlin, SC 2017, 'A radiographic study of permanent molar development in wild Virunga mountain gorillas of known chronological age from Rwanda', American Journal of Physical Anthropology. https://doi.org/10.1002/ajpa.23192
Kralick, Alexandra E. ; Loring Burgess, M. ; Glowacka, Halszka ; Arbenz-Smith, Keely ; Mcgrath, Kate ; Ruff, Christopher B ; Chan, King Chong ; Cranfield, Michael R. ; Stoinski, Tara S. ; Bromage, Timothy G. ; Mudakikwa, Antoine ; Mcfarlin, Shannon C. / A radiographic study of permanent molar development in wild Virunga mountain gorillas of known chronological age from Rwanda. In: American Journal of Physical Anthropology. 2017.
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AU - Kralick, Alexandra E.

AU - Loring Burgess, M.

AU - Glowacka, Halszka

AU - Arbenz-Smith, Keely

AU - Mcgrath, Kate

AU - Ruff, Christopher B

AU - Chan, King Chong

AU - Cranfield, Michael R.

AU - Stoinski, Tara S.

AU - Bromage, Timothy G.

AU - Mudakikwa, Antoine

AU - Mcfarlin, Shannon C.

PY - 2017

Y1 - 2017

N2 - Objectives: While dental development is important to life history investigations, data from wild known-aged great apes are scarce. We report on the first radiographic examination of dental development in wild Virunga mountain gorillas, using known-age skeletal samples recovered in Rwanda. Materials and methods: In 43 individuals (0.0-14.94 years), we collected radiographs of mandibular molars, and where possible, cone beam CT scans. Molar crown and root calcification status was assessed using two established staging systems, and age prediction equations generated using polynomial regression. Results were compared to available data from known-age captive and wild chimpanzees. Results: Mountain gorillas generally fell within reported captive chimpanzee distributions or exceeded them, exhibiting older ages at equivalent radiographic stages of development. Differences reflect delayed initiation and/or an extended duration of second molar crown development, and extended first and second molar root development, in mountain gorillas compared to captive chimpanzees. However, differences in the duration of molar root development were less evident compared to wild chimpanzees. Discussion: Despite sample limitations, our findings extend the known range of variation in radiographic estimates of molar formation timing in great apes, and provide a new age prediction technique based on wild specimens. However, mountain gorillas do not appear accelerated in radiographic assessment of molar formation compared to chimpanzees, as they are for other life history traits. Future studies should aim to resolve the influence of species differences, wild versus captive environments, and/or sampling phenomena on patterns observed here, and more generally, how they relate to variation in tooth size, eruption timing, and developmental life history.

AB - Objectives: While dental development is important to life history investigations, data from wild known-aged great apes are scarce. We report on the first radiographic examination of dental development in wild Virunga mountain gorillas, using known-age skeletal samples recovered in Rwanda. Materials and methods: In 43 individuals (0.0-14.94 years), we collected radiographs of mandibular molars, and where possible, cone beam CT scans. Molar crown and root calcification status was assessed using two established staging systems, and age prediction equations generated using polynomial regression. Results were compared to available data from known-age captive and wild chimpanzees. Results: Mountain gorillas generally fell within reported captive chimpanzee distributions or exceeded them, exhibiting older ages at equivalent radiographic stages of development. Differences reflect delayed initiation and/or an extended duration of second molar crown development, and extended first and second molar root development, in mountain gorillas compared to captive chimpanzees. However, differences in the duration of molar root development were less evident compared to wild chimpanzees. Discussion: Despite sample limitations, our findings extend the known range of variation in radiographic estimates of molar formation timing in great apes, and provide a new age prediction technique based on wild specimens. However, mountain gorillas do not appear accelerated in radiographic assessment of molar formation compared to chimpanzees, as they are for other life history traits. Future studies should aim to resolve the influence of species differences, wild versus captive environments, and/or sampling phenomena on patterns observed here, and more generally, how they relate to variation in tooth size, eruption timing, and developmental life history.

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KW - Gorilla beringei beringei

KW - Radiographs

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