The bony roof of the nose in humans and other primates

The distribution of stresses in the facial skeleton of primates and the dep endence of stress patterns on the general proportions of the facial skeleto n are investigated by means of the finite element method (FEM). In particul ar, the size and position of the nasal aperture and its relation to the orb its have been varied within the limits found in living hominoids. "Biting f orces" are applied to the teeth, bearings are assumed at the frontal bone o r the anterior skull base. The flow of forces is concentrated on the A-shaped "nasal pillars" which sh ow a concave anterior contour. In the high midface of large apes and austra lopithecines a moderate stress concentration in the nasal roof between the orbits can be observed. The low midfaces of modern and undoubted fossil mem bers of the genus Homo the nasal pillars contain weak zones between the orb its, because of the extension of the nasal aperture in the interorbital dis tance, unless the nasal roof is expanded forward in the sagittal direction. The prominence of the nasal skeleton, therefore, sustains the mechanical s tresses which occur in a low and not prognathic hominoid midface. The configuration of monkey skulls with prominent noses is discussed, as we ll as the biological roles of projecting snouts and of low versus high midf aces.