Social Practice and Theoretical Integration of Everyday Life

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

“…It has been repeatedly demonstrated that the variability of bone morphology (including entheses) is multi‐etiological (Foster et al, 2014; Schrader, 2019), involving the pooled effects of genes, sex, biological age, body size, potential pathologies, and other factors (such as nutrition and hormones). Given that all these systemic factors of interindividual variability directly affect the raw size and robusticity of entheses (Karakostis & Harvati, 2021; Schrader, 2019), adjusting entheseal measurements for size can ideally decrease these systemic effects and thus strengthen the signal of bone's biomechanical loading history. For these reasons, controlling for the effects of body size is typically crucial for any anthropological method attempting to reconstruct activity in the past (e.g., Stock & Shaw, 2007).…”

“…These included the calculation of the “relative entheseal size” (Karakostis & Lorenzo, 2016), the “geometric mean approach” (Karakostis et al, 2017; Karakostis & Hotz, 2022), and the use of body mass as a covariate in linear statistical models (Castro et al, 2022). The reason for controlling for the effects of body mass, which is proposed to broadly reflect on various skeletal proxies (e.g., femoral head diameters; Auerbach & Ruff, 2004), is due to its widely reported influence on entheseal variation (e.g., see Foster et al, 2014; Schrader, 2019). In each previous study, the reliability of the applied techniques for eliminating the effects of size was further confirmed using additional statistical analyses.…”

“…Reconstructing habitual physical activity in past human and animal populations is a fundamental objective of bioarcheological sciences (e.g., Schrader, 2019). Several anthropological methods have been proposed for this purpose, relying on the analysis of either external or internal aspects of bone morphology, such as proxies of long bone cross‐sectional strength (e.g., Shaw & Stock, 2009), trabecular architecture (Kivell, 2016), osteoarthritic lesions (e.g., Calce et al, 2017), non‐metric traits (e.g., Trinkaus et al, 2019), and entheses (e.g., Schrader, 2019). The latter structures are defined as the areas of the bones where muscles or ligaments attach.…”

“…However, several previous experimental and/or anatomical studies found no effect of physical activity on entheseal morphology, raising reasonable doubts as to the reliability of these structures for reconstructing habitual muscle recruitment (Rabey et al, 2015; Wallace et al, 2017; Williams‐Hatala et al, 2016; Zumwalt, 2006). Moreover, many approaches for analyzing entheses have been criticized for low intraobserver and interobserver measuring repeatability (Davis et al, 2013; Wilczak et al, 2016), inadequate control for the effects of various systemic factors on entheseal morphology (Schrader, 2019; Villotte & Knüsel, 2013), and the reliance on human skeletal reference collections with limited occupational documentation (Cardoso & Henderson, 2013; Lopreno et al, 2013). Additionally, previous studies have reported a lack of correlation between the ordinal stages of various entheseal scoring systems and the underlying bone microarchitecture (cortical and/or trabecular morphology), which is widely considered to be influenced by biomechanical loading (e.g., Djukic et al, 2015; Michopoulou et al, 2017).…”

“…These results seem to suggest that it is possible for raw entheseal size to reflect habitual physical activity when the signal of biomechanical loading happens to be powerful enough to overcome the effects of other major factors, such as body size, biological age, and genes. However, given that these systemic factors are known to significantly influence raw (unadjusted) entheseal size (Schrader, 2019), it is practically impossible to reliably account for their effects in undocumented bioarcheological samples. Therefore, even though such direct comparisons in raw entheseal size of single entheses can potentially be informative in some cases (and are thus worthy of applying in any study), I would strongly encourage future bioarcheological studies to additionally apply size adjustment, followed by multivariate analyses (see below).…”