Mandibular ramus flexure and gonial eversion as morphologic indicators of sex

Abstract

Recently, two mandibular traits--ramus flexure and gonial eversion--have come under close scrutiny (Loth & Henneberg 1996, 2000). The present study investigates the reliability of these two traits when each is applied as a single and independent indicator of sex, including the question of repeatability. The investigation was designed to give insights into possible confounding factors such as age and remodeling after tooth loss. Two samples, one of forensic (N = 153) and one of archaeological provenance (N = 80), were examined. The forensic sample was evaluated by a single observer while the archaeological sample was independently scored by three different observers. The results document that age and localized tooth loss seriously reduce the accuracy of these traits. For ramus flexure, male accuracy was only 66%, while female accuracy was even lower (32%). Overall accuracy was 59%. It is believed that the original scoring system devised by Loth and Henneberg (1996) creates an inherent bias in favor of males. For gonial eversion, a similar picture emerged (75.4% for males, 45.2% for females and 69.3% overall accuracy). Furthermore, both indicators are prone to intra- as well as inter-observer bias. While both possess some merit as sex indicators, they show marked functional and adaptive responses and may not be suitable for all samples.