Only photos on my best side, please! Implications of bilateral asymmetry of the iliac auricular surface in non‐adult individuals for sex estimation

Abstract

This study aims to address the overlooked effect of bilateral asymmetry for sex estimationin non-adult paired bone structures. Using a recently developed method, disparitiesbetween right and left iliac auricular surfaces (AuSs) were quantified, alsoverifying the effectiveness between sides regarding the percentages of cases correctlyassigned. A sample of 418 AuSs belonging to 209 individuals aged 5 gestationalmonths to 18 years (113 males and 96 females) from the Coimbra, Lisbon, and GranadaIdentified skeletal collections, were studied. They were grouped into two largeage cohorts (≤12 y.o. and 12.1–18 y.o.) based on the onset of menarche. The significantand distinct hormonal fluctuations between sexes in ≤2 y.o. individuals compelledan additional separation. Locomotion issues also imposed grouping individualsfor comparison in non-bipedal (≤1 y.o.) and those who were still achieving emerginggait milestones (1.1–6 y.o.). Overall agreements between sides, sexes, age cohorts,and morphometric variables were compared using Cohen´s κ and intraclass correlationcoefficients, while chi-square and Kolmogorov–Smirnov tests were applied forstatistically significant evaluation. Asymmetry directionality was calculated throughstandardized directional and total asymmetry scores. Slight asymmetries betweensides were identified, becoming the pre-pubertal left AuS more useful for non-adultfemale sexing. Metric variables work better in males, possibly due to the higher variabilityfound in females. Both sexes display a marked age-related change in asymmetryduring puberty (12.1–18 y.o.), with a predominance of the right side in femalesand of the left side in males. Possible explanations for the identified pubertal abruptshifts are discussed considering the various developmental biomechanical milestones.This pioneering study reinforces the complexity of somatic growth and developmentthat characterizes non-adult phenotype, calling for further refinement of sexingmethods considering bilateral asymmetry, and for complementary studies thatdeepen the study of dextralization and its repercussions in adults.