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Facial Asymmetry during Ontogeny

Contact: Franziska Wilke

Facial characteristics are a large part of our identity. Facial asymmetry can provide information on both an individual's genetic and developmental background, and aid in differentiating between populations.  However, a large gap in research persists; there are only a few studies on the changes in facial asymmetry during development.

This project aims to:

  1. Establish an overall asymmetry score for each individual
  2. Establish the age at which asymmetry becomes significant and the age at maximum asymmetry
  3. Assess the variation in magnitude and location of facial asymmetry in regard to age and growth parameters
  4. Assess the variation in magnitude and location of facial asymmetry between the two sexes
  5. Establish the age at which sex differences in asymmetry become significant
  6. Assess the symmetric facial variation within a population
  7. Asses the number, magnitude and location of facial asymmetries within a population
  8. Assess the differences in the location and magnitude of Directional Asymmetries (DA) and Fluctuating Asymmetries (FA) between populations.

Both a longitudinal study and a cross-sectional study will be performed. Individuals between the ages of 2-14 years from four Sub-Saharan African populations (around 250 per location) that differ in both their ethnical composition and socio-economic standing will be scanned and anthropological measurements taken every 6 months. Using geometric morphometrics the difference in facial asymmetries between different ages (cross-sectional), time points (longitudinal) and sexes will be analysed utilizing statistical tests including MANOVA, Principle Component Analysis, and Mahalanobis distances.

Facial asymmetry is expected to increase during growth spurts and sexual dimorphisms to become significant around adolescence. The four populations are expected to show differences in their FAs due to diverse socio-economic conditions, but not in their DAs due to similar genetic backgrounds.