title: Variation at genes influencing facial morphology are not associated with developmental imprecision in human faces.
abstract: Facial asymmetries are commonly used as a proxy for human developmental imprecision resulting from inbreeding, and thus reduced genetic heterozygosity. Several environmental factors influence human facial asymmetry (e.g., health care, parasites), but the generalizability of findings on genetic stressors has been limited in humans by sample characteristics (island populations, endogamy) and indirect genetic assessment (inference from pedigrees). In a sample of 3215 adult humans from the Rotterdam Study, we therefore studied the relationship of facial asymmetry, estimated from nine mid-facial landmarks, with genetic variation at 102 single nucleotide polymorphism (SNP) loci recently associated with facial shape variation. We further tested whether the degree of individual heterozygosity is negatively correlated with facial asymmetry. An ANOVA tree regression did not identify any SNP relating to either fluctuating asymmetry or total asymmetry. In a general linear model, only age and sex--but neither heterozygosity nor any SNP previously reported to covary with facial shape--was significantly related to total or fluctuating asymmetry of the midface. Our study does not corroborate the common assumption in evolutionary and behavioral biology that morphological asymmetries reflect heterozygosity. Our results, however, may be affected by a relatively small degree of inbreeding, a relatively stable environment, and an advanced age in the Rotterdam sample. Further large-scale genetic studies, including gene expression studies, are necessary to validate the genetic and developmental origin of morphological asymmetries.
authors.affiliation: Department of Anthropology, University of Vienna, Vienna, Austria; Konrad Lorenz Institute for Evolution and Cognition Research, Altenberg, Austria.
authors.forename: Sonja
authors.initials: S
authors.lastname: Windhager
authors.affiliation: Department of Anthropology, University of Vienna, Vienna, Austria.
authors.forename: Helmut
authors.initials: H
authors.lastname: Schaschl
authors.affiliation: Department of Anthropology, University of Vienna, Vienna, Austria.
authors.forename: Katrin
authors.initials: K
authors.lastname: Schaefer
authors.affiliation: Department of Theoretical Biology, University of Vienna, Vienna, Austria.
authors.forename: Philipp
authors.initials: P
authors.lastname: Mitteroecker
authors.affiliation: Department of Anthropology, University of Vienna, Vienna, Austria.
authors.forename: Susanne
authors.initials: S
authors.lastname: Huber
authors.affiliation: Department of Anthropology, University of Vienna, Vienna, Austria; Cognitive Science Platform at the University of Vienna, Vienna, Austria; Department of Behavioural Biology, University of Vienna, Vienna, Austria.
authors.forename: Bernard
authors.initials: B
authors.lastname: Wallner
authors.affiliation: Department of Anthropology, University of Vienna, Vienna, Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Fieder
mesh_terms: D000328:Adult; D003710:Demography; D005145:Face / Q000033:anatomy & histology*; D005260:Female; D056426:Genetic Loci; D014644:Genetic Variation; D005828:Genetics, Population; D015894:Genome, Human / Q000235:genetics; D005838:Genotype; D006720:Homozygote; D006801:Humans; D008297:Male; D012044:Regression Analysis