Geometric morphometrics reveals restrictions on the shape of the female os coxae

Abstract

The methodology for sex determination in human skeletal remains depends on the different bone morphologies presented by men and women. Due to their direct implications in reproduction, the whole pelvis, particularly the os coxae, shows different characteristics in either sex. The sacrum and the os coxae constitute the birth canal. In this research study, the os coxae shape is analyzed using geometric morphometrics, providing information on morphology, regardless of size or any other factor beyond the geometry itself. A total of 46 adult ossa coxae from a Spanish archaeological collection were studied using geometric morphometrics. The results show that there is a restriction on the shape of female os coxae. In contrast, male os coxae presents a greater range of variation. The biological reason for this difference is the obstetrical dilemma; a concept defined as the anatomical conflict between bipedalism and the full-term birth of a neonate whose large head requires greater dimensions in the pelvic cavity. Our experimental data reinforce the validity of the obstetrical dilemma as source of the restriction on the shape of female ossa coxae. Additionally, according to the results obtained, size itself does not represent a condition for belonging to one sex or another.

Obstetric dimensions of the female pelvis are less integrated than locomotor dimensions and show protective scaling patterns: Implications for the obstetrical dilemma

“…Mallard et al (2017) found the outlet to be the most integrated part of the pelvis, suggesting higher integration for obstetric measurements. However, since integration reduces variability (Willmore et al, 2007), more highly integrated systems should show lower levels of variation, and the pelvic canal is the most variable region of the pelvis (Candelas González, Rascón Pérez, Chamero, Cambra‐Moo, & González Martín, 2017; Kurki, 2013; Kurki & Decrausaz, 2016). Given these nonintuitive results, a comparison of obstetric and locomotor integration is warranted.…”

Three-dimensional geometric morphometric sex determination of the whole and modeled fragmentary human pubic bone

“…This result alone indicates that this method is effective and that 3-D geometric morphometrics can be used to distinguish between the sexes on smaller portions of the pelvis. Experienced forensic anthropologists using morphoscopic methods can accurately determine sex approximately 90–95% of the time, depending on the state of the bones and the experience of the user [ 1 , 3 , 15 ]. Similar studies, which collected landmarks across the entire os coxa reported similarly high results, so it is promising to see that the method can be narrowed down to a smaller portion of bone and still retain high accuracy [ 3 , 15 ].…”

“…Geometric morphometric analyses are also advantageous because they consist of non-destructive techniques. Metric analyses are also more objective and generally require less training and experience than visual analysis techniques [ 15 ]. Geometric morphometrics is commonly utilized in biological studies and has more recently become a more commonly utilized method of analysis in anthropological studies as well [ 16 – 18 ].…”

“…The first hypothesis guiding this research is that if there are significant differences in the shape of male versus female pubic bones, then a geometric morphometric analysis will be able to distinguish between the two sexes and accurately determine whether an unknown bone belonged to a male or female. The method will be considered accurate if the predictions are consistent with or better than current morphoscopic techniques that can determine sex correctly approximately 90–95% of the time [ 1 , 3 , 15 ]. If the shape differences between males and females are not significant, then the geometric morphometric analysis will be no better than chance, with prediction rates at approximately 50%.…”

Somatometric Characteristics Of Women Of The First And Second Period Of Adulthood Using Different Contraceptives With Different Body Types

“…This phenomenon is based on the study of the variety of physique features of somatotypes. In modern medical anthropology and medicine, the Constitution is evaluated as a complex of individual morphofunctional features of an individual [6]. N. Pende (1922) proposed a classification by predominance functions of one or another endocrine gland.…”