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Tissue-specific behavioural signatures in cortical and trabecular bone. Variations in long bone structure in medieval Britain, and the differential effects of age.



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In this study the structural properties of cortical and trabecular bone in the limbs are compared in three groups from a medieval British population. Since both tissues have been shown to adapt to mechanical loading, anthropologists have interpreted the morphology of either cortical or trabecular bone as a record of loading history. As such, differences in mechanically relevant parameters between populations or species have been considered to present a signature of habitual behaviour during life. Despite a wide appreciation of divergences between the tissues in loading modality and structural configuration, this approach presumes a good agreement between such behavioural signatures in either tissue. Because cortical and trabecular structure are rarely studied together in an anthropological context, it is unclear how biological and structural differences between the tissues may affect the interpretation of behaviour. To this end, diaphyseal cross-sectional geometry and three-dimensional trabecular architecture were quantified in the femur, tibia, and both humeri in three groups from a population from medieval Cambridge, using micro-computed tomography. The thesis is structured as a series of four articles. Three of these explore covariation in cortical and trabecular structural properties and compare the behavioural signatures in the two tissues. To understand some of the observed tissue differences, a fourth article examines the differential effects of age on cortical and trabecular bone. Insights from these chapters are brought together in a final chapter in which the results are integrated. The first two articles deal with variation in lower limb structure between the three groups, which was expected to be low due to the lack of temporal or geographical diversity. Despite correlations between the amount of cortical and trabecular tissue across the sample, behavioural signatures varied between the cortical and trabecular compartments. It was unclear whether the correlations that were observed were the result of functional or systemic influences because of the arguably narrow range of behavioural variation. A more distinctive functional signal was expected between the dominant and non-dominant arm within individuals. In the following chapter it was therefore tested whether humeral bilateral asymmetry in cortical properties corresponds to the bilateral asymmetry in trabecular properties. While it was expected that the dominant arm would have higher values than the non-dominant arm for both cortical and trabecular measures of bone quality, no relationship between hand dominance in either tissue was observed. Despite these discrepancies in behavioural signatures, correlations in structural parameters were as strong as those observed for the lower limb, regardless of whether ipsilateral or contralateral values were used, indicating a major systemic component in the determination of the amount of bone tissue. To explore if age-related bone loss could explain some of the divergences in cortical and trabecular properties, trends in bone structure with age were also analysed. It was found that males and females do not differ in the pattern of trabecular bone loss with age, which commences in early adulthood. In cortical bone major sex differences are observed, however, with greater bone loss in females than in males, and no effect on mechanical competence prior to midlife due to continuing periosteal apposition in both sexes. This illustrates that age-related bone loss differs between cortical and trabecular bone and varies between the sexes, undoubtedly affecting the behavioural signatures in the two tissues differently. While tissue quantities were correlated throughout the limbs, these appeared to be driven primarily by systemic influences. Behavioural signatures were markedly different between the cortical and trabecular compartments, which may not be surprising considering the differential effects of age on the mechanically relevant properties of either tissue. This highlights important differences in the way loading history is reflected in the structural properties of different regions of the skeleton and urges for a better integration of the study of cortical and trabecular structural variation in past populations.





Stock, Jay


Trabecular bone, Bone functional adaptation, Bone metabolism, Habitual behaviour


Doctor of Philosophy (PhD)

Awarding Institution

University of Cambridge
Wellcome Trust (200368/Z/15/Z)
Wellcome Trust Collaborative Grant 2000368/Z/15/Z