Halszka Glowacka is a PhD candidate at Arizona State University. She was awarded a grant during our spring 2015 cycle for her project entitled "Biomechanical constraints on molar emergence in primates."
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.
My study will examine molar emergence as part of a developing functionally integrated chewing system. Molars function with the jaws and chewing muscles to break down food. Developmental coordination among these parts of the chewing system is critical for food ingestion throughout life. In adult primates, the configuration of the chewing system constrains the position of molars to avoid damage to the temporomandibular joint during chewing. Using 3D coordinate data from cross-sectional ontogenetic samples of primate skulls (n = 18 species) I will determine if the position of molar emergence is constrained in the same manner, thereby regulating the timing of molar emergence.
My research will determine how ontogenetic changes in the configuration of the chewing system drive variation in molar emergence schedules among primates and may suggest that life history is closely associated with molar emergence ages vis-à-vis its influence on facial growth rates. It will further suggest that selection for shorter faces and a prolonged growth schedule in the lineage leading to humans would have had the concomitant effect of delaying molar emergence.