Dental tissue proportions in fossil orangutans from mainland Asia and Indonesia

  • Tanya M. Smith Harvard University
  • Anne-Marie Bacon CNRS, Dynamique de l'Evolution Humaine: Individus, Populations, Espèces
  • Fabrice Demeter Muséum National d'Histoire Naturelle
  • Ottmar Kullmer Senckenberg Research Institute
  • Kim Thuy Nguyen Vietnam Academy of Social Siences
  • John de Vos Netherlands Center for Biodiversity
  • Wang Wei Natural History Museum of Guangxi Zhuang Autonomous Region, Nanning, China
  • John P. Zermeno Harvard University
  • Lingxia Zhao Chinese Academy of Sciences
Keywords: Enamel thickness, primate evolution, Pongo, dental morphology, human evolution


Orangutans (Pongo) are the only great ape genus with a substantial Pleistocene and Holocene fossil record, demonstrating a much larger geographic range than extant populations. In addition to having an extensive fossil record, Pongo shows several convergent morphological similarities with Homo, including a trend of dental reduction during the past million years. While studies have documented variation in dental tissue proportions among species of Homo, little is known about variation in enamel thickness within fossil orangutans. Here we assess dental tissue proportions, including conventional enamel thickness indices, in a large sample of fossil orangutan postcanine teeth from mainland Asia and Indonesia. We find few differences between regions, except for significantly lower average enamel thickness (AET) values in Indonesian mandibular first molars. Differences between fossil and extant orangutans are more marked, with fossil Pongo showing higher AET in most postcanine teeth. These differences are significant for maxillary and mandibular first molars. Fossil orangutans show higher AET than extant Pongo due to greater enamel cap areas, which exceed increases in enamel-dentine junction length (due to geometric scaling of areas and lengths for the AET index calculation). We also find greater dentine areas in fossil orangutans, but relative enamel thickness indices do not differ between fossil and extant taxa. When changes in dental tissue proportions between fossil and extant orangutans are compared with fossil and recent Homo sapiens, Pongo appears to show isometric reduction in enamel and dentine, while crown reduction in H. sapiens appears to be due to preferential loss of dentine. Disparate selective pressures or developmental constraints may underlie these patterns. Finally, the finding of moderately thick molar enamel in fossil orangutans may represent an additional convergent dental similarity with Homo erectus, complicating attempts to distinguish these taxa in mixed Asian faunas. 


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Author Biographies

Tanya M. Smith, Harvard University
Department of Human Evolutionary Biology
Fabrice Demeter, Muséum National d'Histoire Naturelle

Dépt. Homme, Nature, Sociétés, Ecoanthropologie et Ethnobiologie

Ottmar Kullmer, Senckenberg Research Institute
Department of Paleoanthropology and Messel Research
Kim Thuy Nguyen, Vietnam Academy of Social Siences
Institute of Archaeology
John de Vos, Netherlands Center for Biodiversity
Department of Geology
John P. Zermeno, Harvard University
Department of Human Evolutionary Biology
Lingxia Zhao, Chinese Academy of Sciences
Institute of Vertebrate Paleontology and Palaeoanthropology
How to Cite
Smith, T., Bacon, A.-M., Demeter, F., Kullmer, O., Nguyen, K. T., de Vos, J., Wei, W., Zermeno, J. P., & Zhao, L. (2011). Dental tissue proportions in fossil orangutans from mainland Asia and Indonesia. Human Origins Research, 1(1), e1.
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