Genetic and environmental influences on facial profile.

Observed variation in facial morphology results from the influences of both genetic and environmental factors. To investigate the role of genetic influences on variation in facial profile, lateral photographs of 23 male and 19 female monozygous (MZ), and 15 male and 22 female dizygous (DZ) twin pairs were selected from the records of the South Australian Twin Study. Soft tissue landmarks and facial profiles were identified, traced and digitized. Linear and angular measures defined by the landmarks were calculated and a series of Fourier functions derived to describe the facial profiles. These Fourier amplitudes were interpreted in terms of the specific regions which they represented. Correlations within MZ pairs were consistently higher than within DZ pairs for both the facial dimensions and the Fourier amplitudes, providing evidence of significant genetic contribution to facial convexity, facial height and facial depth. Variability in nose and lip morphology appeared to be under stronger environmental influence.