The ontogenetic trajectory of the phenotypic covariance matrix, with examples from craniofacial shape in rats and humans

The study examines the ontogenetic course of the phenotypic covariance structure by analyzing the age-specific covariance matrices of shape coordinates for postnatal craniofacial growth in rats and humans. Results show that age-specific population covariance matrices change through postnatal development in both species, with the time course and pattern of changes illustrating the onset and offset of the developmental processes.