The role of postnatal growth pattern in the production of facial morphology

We apply a new morphometric technique in a comparative study of facial growth patterns in three primate species Macaca fascicularis, Cercopithecus aethiops, and Cebus apella. This method, Euclidean distance matrix analysis (Lele, 1991, Am. J. Phys. Anthropol. 85:407-418; Lele and Richtsmeier, 1991, Am. J. Phys. Anthropol. 86:415-428), enables a three-dimensional description of differences in facial geometries and statistical testing of differences among forms. We adapt the method to enable comparison of growth patterns among species and to produce hypothetical forms by joining the immature morphology of a given species with the growth pattern of another species. Our results demonstrate the unique properties of postnatal growth patterns for the three species considered. Interspecific differences in adult skeletal morphology are more than an extension of the morphological differences established during prenatal ontogeny. Statistical tests for difference in form between the hypothetical forms and samples of real forms demonstrate that differences in immature facial morphology established by prenatal growth patterns cannot totally account for the suite of differences in adult facial morphologies. Some components of adult morphology are influenced strictly by differences in postnatal growth. We present suggestions for future use of our methodology for the comparison of growth patterns, including the investigation of phylogenies using growth pattern data.