Evaluation of the auricular surface method for non-adult sex estimation on the Lisbon documented collection

Objectives: Sex is usually not estimated in skeletonized non-adult individuals because sexual dimorphism is considered minimal before puberty. In 2017, a new approach based on the shape of the auricular surface was proposed, showing that this anatomic area of the ilium is dimorphic. This study tests the reproducibility and evaluates the accuracy of the method in a bigger sample.

Materials and methods: Thirty males and 31 females from the Lisbon Collection (1 day-18 years old) were analyzed by two researchers, one experienced, and the other without previous knowledge of the method. The sample was divided into three groups according to prepubertal and pubertal hormonal peaks (<2, 0-12, and 13-18 years old). Two metric variables (DE/AD and FI/CF ratios), two morphological features (Overall Morphology, OM and Morphology of the Retroauricular End of the Superior Demiface, MRS), and two formulae were tested based on the adequate results obtained in the original article.

Results: Data shows a low interobserver error (ICC > 0.92; K > 0.74). Morphological features provide better results than the metrics (DE/AD = 77.05%; FI/CF = 73.77%; OM = 80.33%; MRS = 85.24%). The discriminant function correctly classified 86.66% of the males and the logistic regression, 83.33%. The method was equally reliable in 0-12 and 13-18 years-old age groups and more accurate in males. The accuracy of most of the variables reached 100% for males under 2 years-old, and the probabilities were higher than for older individuals. The percentages of correct estimations are not influenced by the age, year, and cause of death.

Discussion: Despite the relatively small sample size, this study confirms the usefulness of the auricular surface for non-adult sexual estimation, especially for those younger than 2 years old. Additional validation tests in documented individuals from other geographic regions are suggested.