| Most morphometric research assumes stability in the adult craniofacial complex. Many studies, however, have shown significant age-related craniofacial change long after maturity in adults. This study sought to comprehensively test the possibility of adult craniofacial change in a three-dimensional analysis, and to characterize these changes such that researchers may redesign and reinterpret their analyses in light of adult craniofacial variability. To accomplish this, landmark coordinate data for 115 craniofacial landmarks from the cranial vault, face, endobasicranium, ectobasicranium, and mandible were collected from 1054 adult skeletal specimens. Four different geographic/ethnic subgroups were sampled: Black Americans, White Americans, White South Africans, and South African Zulus. Individuals ranged from twenty to ninety-nine plus years of age. Craniofacial form was compared between adult age groups within each geographic/ethnic identity and sex using Euclidean Distance Matrix Analysis (EDMA). Craniofacial shape change with age was also compared using EDMA. General linear regression and ANCOVA analyses were employed as supplementary tests of adult age-related craniofacial variability. Results indicate that there are many significant age-related differences in adult craniofacial morphology. These differences are not limited to any craniofacial region, age comparison, or population. Most of these age-related differences range between five and ten percent with age; however, some are as large as twenty-three percent. Many of the largest and systematic changes occur in the mandible and are probably related to edentulism. However, results also indicate significant age-related differences unassociated with the mouth or edentulism. For example, many linear distances in the endo- and ectocranial base show significant age-related change, despite the basicranium's traditional characterization as a stable region. Adult age-related changes show few systematic trends across populations, sex, or craniofacial regions, however, the overwhelming number of significant differences found between adult age groups leaves no doubt that adult craniofacial morphology is dynamic and craniofacial analyses that use adult human comparison samples need to, in many cases, control for this significant age-related variability. Linear distances representing cranial vault height and length, and mandible and ectobasicranial width rarely showed significant age-related differences, indicating that they are good candidates for tests of stability with other methods. |
