Growth and development of the fetal craniofacial complex in humans (Homo sapiens) and pigtailed macaques (Macaca nemestrina): A 3D-CT comparative analysis

This study compares fetal craniofacial growth patterns of macaques and humans to determine if a common growth pattern exists. The fetal populations consist of 16 male pigtailed macaques (mean age 21 weeks) and 17 humans (9 males and 8 females; mean age 29 weeks). The macaque population completed 86% of their gestation, while the human population completed 72%. For each individual, three-dimensional coordinates of 20 landmarks on the skull were collected from 3D-CT-reconstructed images and 2D axial slices. Early and late groups were created from the human (early mean age 25 weeks, N=8; late mean age 34 weeks, N=9) and macaque populations (early mean age 16 weeks, N=7; late mean age 23 weeks, N=9). Inter- and intraspecific comparisons were made between the early and late groups. To determine if macaques and humans share a common growth pattern, human growth estimated from a comparison of early and late groups was compared to the pattern of growth estimated between early and late macaque groups. Euclidean Distance Matrix Analysis (EDMA) was used in all comparisons. Intraspecific comparisons indicate that the growing fetal skull displays the greatest amount of change along mediolateral dimensions. Changes in shape during human growth are primarily localized to the basicranium and palate, while macaques experience localized change in the midface. Interspecific comparisons indicate that the two fetal populations differ primarily on the basis of the comparatively large midface of the macaques. Results of a statistical comparison of growth patterns indicate that the two primate species do not share a common fetal craniofacial growth pattern. The macaque pattern is characterized by increased midfacial growth relative to humans. Our results suggest that morphological differences in the craniofacial skeleton of these species is in part established by differences in fetal growth patterns.

 Images from the publication. The blue reconstruction (left) is from a fetal pigtailed macaque and the pink reconstruction (right) is from a fetal human.