Der BAG-Förderpreis 2021 für Dissertationen wurde heute an Lukas Waltenberger, BSc, MSc, PhD, Österreichisches Archäologisches Institut (ÖAI) der Österreichischen Akademie der Wissenschaften (ÖAW), verliehen. Der Vorstand der BAG gratuliert aufs Herzlichste!

Titel der Abschlussarbeit

Parturition scars as evidence of birth? A geometric morphometric reappraisal of pelvic features

Abstract

Pelvic features, mostly known as parturition scars, have been frequently studied in the last fifty years. They are commonly located close to the sacroiliac joint (preauricular sulcus, margo auricularis groove, interosseus groove, preauricular extensions), or at the pubic bones (dorsal pubic pitting, ventral pubic pitting, extended pubic tubercle, exostoses at the pectineal line). Many published articles came to inconclusive results about the association of pelvic features with birth because pelvic features also develop in nulliparous females and even in males (e.g., Cox 1989). Besides pregnancy and birth, other factors such as hormonal status, biomechanical strain, body height, body weight, or age are suspected to influence the expression of pelvic features (e.g., Maass 2012), but these effects were rarely tested. In my dissertation, I assessed the association of pelvic features with various potential causes as well as with pelvic shape. The pelvis constantly transfers body weight from the trunk to the legs and therefore experiences considerable biomechanical strain. Because stress to bones often causes bone remodelling, I assumed that the development of pelvic features and shape remodelling co-occur during growth as well as during adulthood. In a first methodological study, I tested several photogrammetric software packages and compared results obtained by CT scanning, 3D structured light scanning, photogrammetry, and Microscribe Digitizer. In this study, I used three different samples, an Austrian Bronze Age sample, a 19th century sample from Austria, and modern CT data from New Mexico, USA, and provided guidelines about the use of photogrammetry to create 3D surface meshes of articulated pelves for further analysis. Subsequently, I analysed adult pelvic shape variation and compared this data with the expression of pelvic features in adulthood using landmark data and geometric morphometric methods (Principal component analysis, Partial Least Squares Analysis, Multivariate Linear Regression, and Procrustes ANOVA), a moving average algorithm, and multiple regression. My results indicate a complex pattern of association of various factors, such as the number of births, body weight, stature, age, and centrum-collum-diaphyseal angle (CCD-angle). Only dorsal pubic pitting was significantly associated with pregnancy and birth, which I then used to develop a formula to predict the number of birth events from dry bone material. Although, this approach is not reliable for the prediction of single individuals, it has potential to compare the average number of birth events between different populations. Furthermore, the preauricular sulcus and margo auricularis groove were significantly associated with pelvic shape, particularly with a retroverted acetabulum, showing that some pelvic features are more related to biomechanical stress and aging than to birth stress. The analysis of pelvic shape changes during adulthood showed that shape changes remained relatively stable in males with two similar phases of remodelling, three different phases of shape change were observable in females, reflecting a combination of hormone-driven and stress-related bone remodelling during and after the reproductive period. Finally, photogrammetry, CT scanning and 3D structured light scanner provide comparable surface meshes. However, photogrammetry needs lot of training to produce high quality surface meshes. The results of this thesis indicate that the effect of single causal factors on the expression of pelvic features are small, but there is indeed an association of some pelvic features with pregnancy and birth. By a multivariate approach and comprehensive samples, I was able to disentangles the various factors and show the possibilities and limitations of pelvic features in bioarcheological and forensic applications.