Sexual dimorphism in crania belonging to the 1st century AD from the tomb of Mentuemhat (TT34), Luxor, Egypt

Abstract

The objective of this study was to analyze the degree of sexual dimorphism of the crania found in room 127 (tomb TT34, Thebes) and to estimate the role of morphometric dimensions in sexual dimorphism. We studied 43 female and 41 male crania. Forty-four metric measurements were taken and 31 indices were calculated. Differences were evaluated using chi-square and Student’s t-tests. A stepwise discriminant analysis with cross-validation was applied. The Sexual Dimorphism Index (SDI) indicates that the values of all variables are higher in males except for the minimum width of the nasal bones and the facial angle. The highest SDI values are observed in the bizygomatic width and in the variables that measure the size of the maxilla (palatal area). In the indices, the biggest differences are found in the craniofacial index (P < 0.001). Using variables of the neurocranium and splanchnocranium, several highly reliable discriminant functions have been obtained. The most dimorphic variables are related to regions where the cranium connects to the muscles that keep the head upright and allow tilting and rotating movements in relation to the trunk. The bizygomatic width and the external biorbital width are the most dimorphic of the facial region, differences that are justified by a greater convexity of the zygomatic arch which could be related to a hypertrophy of the temporal muscle. The width of the zygomatic arch, its robustness, and the resulting degree of sexual dimorphism may be due to dietary and/or cultural habits related to chewing and the use of the mouth as a tool.