TRANSITIONS was structured into a developmental and applicative phase. The first part of the project focussed on the creation of a new open-source toolkit (morphomap) providing functions to extract from CT data, the segmented long bone of interest and based on that, morphometric and biomechanical parameters together with maps of cortical bone distribution along the entire diaphysis of long bones (Figure 1).
The Covid pandemic had a major impact on my ability to travel to gather CT data from archaeological populations as intended. Therefore the focus was shifted more towards what could be achieved by working remotely – detailed software development and assessment of data from living populations available in a novel database, accessible via the internet to establish the baseline understanding in modern populations that can be applied to archaeological material, which we expect will become available again in the next year or two. This shift was actually very beneficial in that by first understanding how bones adapt to activity and body proportions in a well characterised modern sample with detailed life history and activity records we are now in a much better position to interpret the less well characterised archaeological material by reference to this unique modern sample.
During the project an extensive database of 3D models of long bones was built from CT data of recently deceased female and male individuals (NMDID database). In detail 3D models of the humerus and femur from more than 200 individuals were generated. The 3D models were processed using the new software, developed further within the project, morphomap to extract from the entire diaphysis the information related to shape, biomechanical parameters and cortical thickness.
The distribution of cortical bone in the femora of males and females is mainly influenced by body proportions (weight, height and long bone length) and age. Loading history in recent human individuals does not appear to influence significantly the distribution of cortical bone. In women, age influences more strongly the cortical thickness of the femur than any other variable, probably in relation to osteoporosis (Figure 2). Interestingly, the analysis of the upper limb reveals that males are more asymmetric than females. In adults, asymmetry of cortical thickness in the humerus decreases with increasing of age.
In conclusion, the project TRANSITIONS found that factors external to the occupational and recreational loading history of an individuals such as weight, height and age are most important in influencing the overall thickness and distribution of cortical bone in the femur and humerus. In addition, some of these variables have an impact on the distribution of the cortical bone in different ways.
