The effects of race, sex, and nutrition on craniofacial differentiation in rats. A multivariate analysis

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Abstract
Wistar and Holtzman rats were fed (a) control diet ad libitum (controls); (b) restricted control diet (undernourished); and (c) low‐protein diet ad libitum (malnourished), from weaning to 70 days of age. Mahalanobis D2 distances between cranial groups were assessed. Besides, differences among traits were assessed by the analysis of variance and Tukey test. The relative influence of each factor yielded a decreasing sequence: protein‐calorie malnutrition (PCM)‐Protein deficit (PD)‐race‐sex. However, this sequence differed between races. The significant sexual dimorphism in Wistar controls disappeared because of PCM and PD. Race and sex, race and nutrition, and race, sex, and nutrition interacted. Traits were classified into: (a) specific, (b) nonspecific, and (c) invariable. The specific race traits were alveolar length and foraminal width. The specific nutritional traits were neurocranial and splanchnocranial lengths and heights, alveolar and neurocranial widths, and the neuro‐splanchnorcranial index (NSI) and the neurocranial vertico‐transversal index (NVTI). There were no specific sexual traits. It was concluded that nutritional factors can modify a taxonomic distance in three different ways: (a) evoking morphological differences among populations of the same racial group, (b) altering differences among racial groups, and (c) modifying the pattern of sexual dimorphism of a population. It is suggested that craniological studies should take into account only the set of specific traits, disregarding both specific traits due to other factors and nonspecific ones.