This research develops a model of primate skull growth in a well-established experimental species (rats) that mimics temporal fluctuations in environmental resources. Novel integrative analyses involving imaging, morphological metrics, histology, and serology typify the skeletal morphology and physiology associated with postnatal variation in dietary properties and feeding behavior. The multidisciplinary nature of this study provides a number of unique opportunities to develop collaborations between research and medical facilities, and to promote student training. Results will be disseminated at scientific and public forums, and will have broader implications for human craniofacial health as it relates to diet and numerous disorders affecting oral utility.
The evolution and function of the human skull is intimately related to the mechanical demands imposed by food items. Throughout primate and human evolution, these dietary resources have often been seasonal, resulting in the cyclical consumption of difficult-to-process "fallback foods." This dietary seasonality has often been invoked in ecological interpretations of fossil human ancestors and relatives, such as Paranthropus. However, despite the temporal and spatial complexity of primate diets, there is little work related to the impact of seasonality in dietary properties on craniofacial development. This greatly hinders our understanding of primate ecology and evolution as well as the influence of feeding behaviors for bone biology and human craniofacial health. To address this significant gap, this research uses rats to test how changing dietary resources across time are affected by fallback foods in underlying skeletal development of the face. The research will use a variety of imaging techniques to examine differences between those animals that are fed fallback foods and those that are not. Such modern methods bridge the gap between laboratory- and field-based analyses of skeletal growth in primates. A longitudinal approach will elucidate the effect of behavioral variation on craniofacial morphology and physiology across the entire growth period, providing insight into skull development at multiple organismal levels. A more complete understanding of the way environment impacts organismal form will shed light on the association between skeletal biology and dietary variability,
The skeleton is a dynamic, living organ and as such responds to the mechanical demands placed upon it by everyday activities. This research investigates how changes in diet affect interactions between the skull and chewing muscles, which in turn affect the growth and health of the skull. Little is known about the impact of a changing diet on an individual’s health, despite the fact that seasonality is common in non-industrialized societies as well as in non-human primates. Changes in diet and chewing behavior are also associated with human skull disorders, such as temporomandibular joint disorder (TMJD) and tooth loss. This project shows that an increase in the hardness/toughness of diet during an individual’s lifetime can increase bone growth rate in the jaws, strengthen bone through increased collagen production, reduce levels of bone resorption, and affect the anatomy of the temporomandibular joint (TMJ) and the bony attachment sites for chewing muscles. However, a decrease in hardness/toughness of diet – as may be associated with human clinical disorders related to aging – is related to decreased bone growth in the jaw and anatomical features similar to individuals who have never experienced substantial chewing loads. Results from this study suggest that for biologists, changes in diet related to seasonal cycles make it more difficult to infer behavior from anatomy. For clinicians, changes in diet related to aging and jaw disorders may actually aggravate loss of bone mass and strength in the skull. This project highlights the importance of understanding how changes in behavior within an individual’s lifetime impact growth and health. It also underscores the need for more realistic experimental modeling of these variable behaviors. A more complete knowledge of how environmental factors (such as diet) influence skeletal growth has significant implications for the biology of living and fossil species, as well as clinical importance for human patients with disorders affecting the teeth and jaws.
