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Skull Growth and Biomechanical Constraints on Molar Emergence in Primates

illustration of lemur skull

Among primates, there is a strong relationship between life history and the age at which the first permanent molar emerges into the mouth.  However, knowledge of how variation in molar emergence age arises and why it is closely associated with life history is lacking. This doctoral dissertation research project will examine molar emergence as part of a developing functionally integrated chewing system.

Human life history is unique among living primates. Humans grow slowly and have long lifespans coupled with short inter-birth intervals, resulting in fast reproductive rates.

Among primates, there is a strong relationship between life history and the age at which the first permanent molar emerges into the mouth. Paleoanthropologists use this relationship to probe the antiquity of the unique human life history profile, but knowledge of how variation in molar emergence age arises and why it is closely associated with life history is lacking.

This doctoral dissertation research project will examine molar emergence as part of a developing functionally integrated chewing system.

Using 3D coordinate data from cross-sectional ontogenetic samples of primate skulls (n = 18 species; 1182 specimens), this study will determine if the position of molar emergence is constrained by the biomechanics of mastication.

Identifying the mechanism that modulates coordinated growth of the chewing system will provide a model for contextualizing variation in the timing of molar emergence among primates. It will also contribute to understanding the close association between molar emergence and life history.

Funding Source:
National Science Foundation 

Halszka Glowacka, Arizona State University School of Human Evolution and Social Change
Gary Schwartz, Arizona State University School of Human Evolution and Social Change