Reflections of manual labor in the hand entheses of early industrial women workers with extensively documented life histories

Abstract

ObjectivesSex‐based occupational variability constitutes a fundamental component of human behavior and a major focus of research focusing on biocultural evolution. However, the reliability of reconstructing physical activity in past women is often compromised by the lack of female skeletal collections with adequately documented lifetime occupations, domestic living conditions, medical records, and socioeconomic status. Here, we attempt to reconstruct habitual manual activity in a skeletal sample of early industrial women with uniquely archived life histories.Materials and MethodsWe rely on the application of our “Validated Entheses‐based Reconstruction of Activity” method on the hand skeletons of 38 extensively documented individuals from the Basel‐Spitalfriedhof collection. Our comparisons also include 40 documented males from the same collection.ResultsAs expected, we found evidence of increased entheseal variability among women sharing the same unspecialized occupation (maids and factory workers). Moreover, certain entheseal patterns were almost exclusive to the men involved in occupations not associated with the female sex (mainly construction workers). Importantly, all six women known to have practiced more specific occupational activities (e.g., seamstresses) showed distinctive entheseal patterns, seemingly associated with more demanding physical practices. This within‐sex variation was not correlated with differences in biological age, estimated body size, socioeconomic status, relatedness, or the presence of reported children.DiscussionOur findings directly reflect the rich historical sources on the working lives of low‐status women in early industrial Basel. These results highlight the high potential value of our documented sample as a reference basis for reconstructing the division of labor in bioarchaeological contexts.

Statistical protocol for analyzing 3D muscle attachment sites based on the “Validated Entheses‐based Reconstruction of Activity” (VERA) approach

“…Consequently, a PCA on raw entheseal values showed clear variation between runners and controls on the PC2 axis, which showed positive loadings for all three entheses (Figure 3). Similarly, in previous studies on extensively documented human skeletal samples (Karakostis & Hotz, 2022;Karakostis et al, 2017), the observed occupational trends were distinctive both in the size-adjusted PCA and the raw PCA.…”

“…In brief, the steps are the following: Development of 3D surface models (a), pseudocoloring the bone surface using the "equalize vertex colors" filter (b), pseudocoloring the bone surface by curvature based on the filter "discrete curvatures" (c), rough selection of the entheseal surface plus a thin zone of the flatter surrounding (non-entheseal) bone area (d), delineation of the exact entheseal borders after using the filter "curvature principal directions" or "calculation of geodesic distances", which highlight entheseal borders (e), cropping of the surrounding nonentheseal bone area (i.e., blue zone in panel e), and measuring entheseal surface size in mm 2 (f). More details and illustrations can be found in several previous studies (Castro et al, 2022;Karakostis et al, 2020;Karakostis & Hotz, 2022;Karakostis, Jeffery, & Harvati, 2019;Karakostis & Lorenzo, 2016). [Colour figure can be viewed at wileyonlinelibrary.com] size proxies (bone length and articular surface area size), age group, and biological sex.…”

“…[Colour figure can be viewed at wileyonlinelibrary. com] PC scores of interest and various systemic factors, such as biological age and estimated stature or body mass (e.g., Karakostis et al, 2017;Karakostis & Hotz, 2022;Karakostis & Lorenzo, 2016;Karakostis, Wallace, et al, 2019).…”

“…In contrast, longterm workers with finer and/or semi-mechanized occupations showed an entheseal PC pattern reflecting thumb-index finger precision grasping. Importantly, the scores of this specific PC were not found to be associated with variation in population origin, socioeconomic status (based on recorded property lists), pathologies (based on official medical records), biological age, estimated body size, sexual dimorphism, or direct genetic relations (based on the individuals' detailed genealogical profiles; (Hotz, 2017;Hotz & Steinke, 2012;Karakostis et al, 2017;Karakostis & Hotz, 2022). In fact, the only PC axis that showed correlation with estimated body size and/or age was PC1 based on raw (unadjusted) entheseal measurements, which did not typically reveal any activity-related differences in previous studies (e.g., Karakostis et al, 2017;Karakostis & Lorenzo, 2016; also see Milella et al, 2015).…”

“…Even though the raw (unadjusted) size of each enthesis is known to be strongly influenced by the systemic effects of various factors besides activity (e.g., Karakostis et al, 2017;Karakostis & Hotz, 2022), a previous experimental study found significant differences between activity groups in the raw entheseal 3D size of single entheses (Castro et al, 2022). This was a recent laboratory study on house mice, which compared habitual voluntary runners to controls based on a mixed linear model that used body size as a covariate.…”