Variability in the Size of the Mastoid Process in African-American and Caucasian Populations of Male and Female Skulls

Haponek, Greg, Brittney Kittrell, and Mary Tracy-Bee

Variation in mastoid process morphology related to sex, age, and race was investigated in modern human skulls from Caucasian and African-American populations from United States.  While the age and race exhibited little to no significant difference associated with mastoid process dimensions, sex differed significantly for nearly all of the mastoid measurements conducted.  Males exhibit longer and wider mastoid processes.  Other soft tissue and general skull morphology measurements were larger in males relative to females as well. While other studies conducted on earlier humans and modern humans of different races identified a difference in size and shape of mastoid process dimensions, our results provide insight into the similarity or convergence of this trait occurring in both races. Directional asymmetry exists in all mastoid process measurements.  A left-sided dominance was found to occur when using measurements related to the Zoja technique, while a right-sided dominance was identified when taking measurements using the Frankfurt horizontal or when applying Broca’s technique.  This provides insight into the variability of different methods used when measuring the mastoid process.