Heritability of human cranial dimensions: comparing the evolvability of different skull regions

MARTÍNEZ ABADÍAS, NEUS; GONZÁLEZ-JOSÉ, ROLANDO; TORSTEIN SJOVOLD,; P KLINGENBERG, CHRISTIAN; MAURO SANTOS,; MIREIA ESPARZA,; MIQUEL HERNÁNDEZ,

Budapest

Congreso; 15th European Congress of the Anthropological Association; 2006

Quantitative traits, such as craniometrical traits, have been successfully incorporated into model-bound genetic-population methods in order to provide insight into human prehistoric populations’ structure. It has been evidenced that genetic variation can be inferred from phenotypic variation, because of the high correlation between their variance-covariance matrices. However, little is still known about the degree of genetic and non-genetic influences on the phenotypic expression of more specific, functionally based traits. Thus, a subject matter of quantitative analysis is the heritability of complex metric traits, which is the proportion of total phenotypic variation due to additive genetic variation. Moreover, it also provides an estimate of the environmental variation. Therefore, the potential influence of natural selection on particular structures of the skull can be inferred. A large and pedigree-structured skull series from Hallstatt (Austria) has been analyzed by means of 3D geometric morphometric techniques. The sample includes 315 adult complete skulls. Heritability estimates for 60 linear distances have been computed following an animal model and by applying restricted maximum likelihood methods. Distances have been assigned to different regions in the skull to compare their heritable behaviour. Results show that the heritability of cranial dimensions is low to moderate. Total cranial dimensions (such as maximum length and breadth), as well as those of facial structures, are the most heritable. The basicranium provides the lowest heritability estimates, being most of them non-significant. Standardized coefficients of variation were estimated in order to compare the evolvability of traits, that is, their ability to respond to selection. Traits with higher heritabilities tended to show higher additive genetic variability. As expected, the facial and neural regions showed the highest evolvabilities. However, the cranial base, despite showing low heritability and high residual variation, also showed moderate to high capability to evolve.