The effect of diet and sociopolitical change on physiological stress and behavior in late Roman‐Early Byzantine (300–700 AD ) and Islamic (902–1,235 AD ) populations from Ibiza, Spain

Objectives:
This study evaluated chronological changes in physiological stress and levels of habitual loading of Ibizan populations from the Late Roman-Early Byzantine to the Islamic period (300-1235 AD) using measures of body size and bone cross-sectional properties. It also explored the effect of diet, modeled using stable isotopes, on physiological stress levels and behavior.
Materials and Methods:
The sample comprised individuals from three archaeological populations: Urban Late Roman- Early Byzantine (LREB) (300-700 AD), Medieval Urban Islamic (902-1235 AD), and Rural Islamic. Bone lengths, femoral head dimensions, and diaphyseal products and circumferences were compared to assess differences in body size and habitual loading in 222 adult individuals. Ordinary least squares regression evaluated the correlations between these measures and carbon (δ13C) and nitrogen (δ15N) stable isotope ratios in 115 individuals for whom both isotope values and osteological measures are available.
Results: The Rural Islamic group had shorter stature and reduced lower limb cross-sectional properties compared to the two urban groups. In both LREB and Islamic groups, body mass and femur length was positively correlated with δ13C values, and δ15N shows a positive correlation with left humerus shape in the LREB Urban sample.
Conclusions:
The low stature and cross-sectional properties of the Rural Islamic group are most likely an indicator of greater physiological stress, potentially due to poorer diet. Positive correlations between measures of body size and δ13C values further suggest that greater access to C4 resources improved diet quality. Alternatively, this relationship could indicate greater body size among migrants from areas where individuals consumed more C4 resources.