1Department of Human Evolutionary Biology, Harvard University, 2Department of Oral Anatomy, School of Dentistry, Aichi Gakuin University, 3Department of Anthropology, Wake Forest University
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In 1989 Holly Smith demonstrated that dental development is correlated with life history traits such as gestation length, weaning age, age at first reproduction, and interbirth intervals (IBIs) in a taxonomically broad primate sample. These patterns have been extended to reconstruct hominin life histories, although the robusticity of this pattern within primate genera remains largely untested. Other scholars have suggested that folivorous primates show more rapid development than frugivorous species, or that smaller primates show faster development than larger ones. In order to investigate these associations, we compare molar calcification and eruption in 64 known-aged juvenile macaques (Macaca arctoides, Macaca fascicularis, Macaca fuscata, and Macaca mulatta) using high-resolution micro-CT scanning and conventional histology. We find that M. mulatta and M. fascicularis have the most rapid molar development, which is consistent with their short gestation lengths and short IBIs (both taxa), less frugivorous diet (M. mulatta), and smaller body size (M. fascicularis). Despite differences in the degree of frugivory and body mass between these two species, there were no marked differences in molar development. In contrast, M. fuscata shows a more prolonged dental development, which is consistent with their slower life histories and larger body mass. Macaca fuscata initiates molar calcification and completes root formation later than the other three species. While we find some support for primate-wide associations between dental development and life history, these associations may be influenced by ecological and physiological factors such as diet, reproductive seasonality, and body mass, even within a relatively closely-related group of primates.
Funded by Harvard University, Wake Forest University, Primate Research Institute Kyoto University, Aichi Gakuin University, and the Nikon Corporation (Japan).