Increased Upper Face Height

Upper facial height in apes and humans is commonly measured as the linear distance between the midline osteological landmarks nasion, at the top of the nose, and prosthion, at the front (anterior) portion of the face just above the crowns of the upper central incisor teeth, thus excluding the lower facial height component made up of the anterior lower jaw (mandibular symphysis). A finer developmental and functional distinction omits the dentognathic portion of the maxillary bone between the anterior nasal spine and prosthion (defined as mid-facial height), and thus defines upper facial height as essentially the vertical component of the nasal complex contained by the maxillary bones. The back (posterior) portion of upper facial height is measured in midline between the optic canal point and the posterior nasal spine. The developmental relationship of anterior and posterior upper facial heights, as well as both of these to other anatomical regions of the skull (neurocranium, basicranium, middle face, and lower face) are important factors determining overall craniofacial differences between apes and humans, as well as more subtle differences found within various ape species, extant humans, and fossil hominin taxa. Varying patterns of integration and modularization of these different skull regions during growth underlie these craniofacial differences, with some aspects appearing relatively earlier in development, and others determined more so by subsequent growth with allometric effects.