Sphenoid Bone Length

The sphenoid, along with the ethmoid and the right and left temporal bones, provides the skeletal link between the face and neurocranium. As the central bone of the cranial base from which the face grows forward, growth in the anterior sphenoid body during early ontogeny determines the spatial relationships between the face, neurocranium, and cranial base. Humans experience less growth in the anterior sphenoid body early in development than do other apes, and accordingly have shorter sphenoid lengths (in the sagittal plane) and reduced facial projection. Sphenoid shortening may be an adaptation for speech, as it results in reduced oropharynx length and contributes to the uniquely human proportions of the vocal tract, allowing humans to make distinct speech sounds.