Researchers have analyzed the developmental processes contributing to craniofacial variation from genetic, evolutionary, biomechanical and forensic perspectives, yet no study has clearly demonstrated the exact anatomical processes that occur in the craniofacial complex during postnatal growth to establish ultimate adult morphologies. Furthermore, previous research has not evaluated how endocranial bones (i.e., the ethmoid and sphenoid) play a role in postnatal craniofacial growth. Thus, while researchers have hypothesized that the long postnatal period of continued growth contributes to the high amount of variation observed in adult facial variation, this has yet to be shown empirically.

The presented research uses cranial data obtained from 299 computer tomographic (CT) scans of juvenile heads to document the growth changes that take place in the mid-face to establish adult human craniofacial variation. The growth trajectories of five developmentally independent regions of the face were studied:​ the frontonasal “module”, the left and right maxillary “modules”, the sphenoid “module”, and the ethmoid “module”. This study examined:​ 1) if developmental “modules” of the face remain proportional to each other throughout postnatal growth;​ 2) which “modules” of the face experience the most shape change during postnatal growth;​ and 3) if males and females have different growth trajectories of the five “modules” under study.

Results of analyses demonstrate clear distinctions between the sexes in growth patterns, as well as between the modules. Analyses within each module indicate that shape changes are occurring locally, while all of the units of the face, with the exception of the ethmoid, are remaining in relatively the same positions throughout growth. Results also reveal that males and females display different growth trajectories for the five “modules” under investigation.

This study applies current hypotheses of postnatal ontogeny to a human skeletal sample of known age and sex, providing support for the early onset of craniofacial variation and differential growth trajectories for males and females. The implications of this study provide important information for our current understanding of postnatal facial growth.