With the Neolithic adoption of agricultural practices around 10,000 BCE came a dietary transition from foraged foods to domesticated crops. A significant reduction in the overall dimensions of the human craniofacial skeleton is associated with both the dietary shift and the decreased biomechanical demands associated with agricultural diets. However, the impact of this dietary transition on specific skeletal structures such as the hard palate is poorly understood. Previous experimental work has shown that laboratory rabbits fed a soft, processed diet have a vertically shallow palate with decreased cortical bone thickness and trabecular area. Here we test the hypothesis that compared to hunter-gatherer populations, human agriculturalists have a similarly reduced palate due to the consumption of softer, more intensely processed foods.

CT scans from a mixed-sex adult sample of Homo sapiens skulls (n=36) representing two pre-industrial agricultural groups (ancient Egyptians and pre-Columbian Peruvians) and two hunter-gatherer groups (indigenous Australians and native Alaskans) were analyzed using 3D Slicer software. The following dimensions were measured at the anterior, middle, and posterior palate: palate width; vertical palate depth; cortical bone thickness along the oral lamina; and trabecular bone area. Palate variables were analyzed using pairwise Mann-Whitney U-tests (α = 0.05). Results show that compared to hunter-gatherers, individuals from agricultural populations have significantly vertically shallow palates, thinner cortical bone at the middle and posterior palate, and decreased trabecular bone area at the middle palate.

These results support the hypothesis that cross-sectional palatal morphology is associated with the biomechanical profile of the human diet, and that the hard palate of modern humans has been significantly affected by the Neolithic adoption of agriculture. The adoption of agriculture decreased the mechanical strain experienced by the hard palate, resulting in a decrease in overall bone volume. We propose that further changes might be expected in palate morphology in more recent human populations, related to increased food processing and reduced dietary breadth seen during the Industrial and Green Revolutions of the mid-17^th through 20^th centuries. Additional research is needed to investigate the effect of industrialized agriculture on palatal morphology, as well as the influence of biomechanical loading on the hard palate across life history and growth.