Quantifying Palaeopathology Using Geometric Morphometrics

Palaeopathology is the study of disease and injury in archaeological bone. Traditional methods rely heavily on macroscopic description which can have a high degree of subjectivity and error, as well as limiting the types of research questions possible. Geometric morphometrics are a suite of shape analysis techniques and provide an opportunity to investigate possible relationships between skeletal morphological variation and disease. This thesis aims to demonstrate the potential of applying these methods in palaeopathological research and the results illustrate the benefits of using quantifiable and objective shape analysis methods in palaeopathology. The first half of the thesis discusses the use of geometric morphometrics to investigate skeletal variation to identify possible aetiological factors in the development of Schmorl's nodes and osteoarthritis. There was a strong association found between vertebral morphology and Schmorl's nodes in the lower spine. These findings have great implications for both bioarchaeological interpretation and clinical understanding of the aetiology and pathogenesis of Schmorl's nodes. Joint morphology of the proximal ulna and distal humerus was found to have no identifiable relationship with osteoarthritis, indicating that joint morphology is not a predisposing factor in elbow osteoarthritis, nor does osteoarthritis deform the joints in a systematic manner. A tentative relationship between eburnation and knee joint morphology was identified, although these results need to be verified with future research. If the association can be supported, shape analyses may provide a way for clinicians to monitor the progression of the disease. Geometric morphometrics were also shown to objectively record pathological shape deformation resulting from leprosy and residual rickets. The ability to objectively describe lesions with quantified data will greatly strengthen palaeopathology by decreasing the subjectivity and error inherent in macroscopic based methods. This thesis represents promising groundwork for the incorporation of geometric morphometrics into palaeopathological research

Spondylolysis and Spinal Adaptations for Bipedalism: The Overshoot Hypothesis

Background and objectives The study reported here focused on the aetiology of spondylolysis, a vertebral pathology usually caused by a fatigue fracture. The goal was to test the Overshoot Hypothesis, which proposes that people develop spondylolysis because their vertebral shape is at the highly derived end of the range of variation within Homo sapiens. Methodology We recorded 3D data on the final lumbar vertebrae of H. sapiens and three great ape species, and performed three analyses. First, we compared H. sapiens vertebrae with and without spondylolysis. Second, we compared H. sapiens vertebrae with and without spondylolysis to great ape vertebrae. Lastly, we compared H. sapiens vertebrae with and without spondylolysis to great ape vertebrae and to vertebrae of H. sapiens with Schmorl’s nodes, which previous studies have shown tend to be located at the ancestral end of the range of H. sapiens shape variation. Results We found that H. sapiens vertebrae with spondylolysis are significantly different in shape from healthy H. sapiens vertebrae. We also found that H. sapiens vertebrae with spondylolysis are more distant from great ape vertebrae than are healthy H. sapiens vertebrae. Lastly, we found that H. sapiens vertebrae with spondylolysis are at the opposite end of the range of shape variation than vertebrae with Schmorl’s nodes. Conclusions Our findings indicate that H. sapiens vertebrae with spondylolysis tend to exhibit highly derived traits and therefore support the Overshoot Hypothesis. Spondylolysis, it appears, is linked to our lineage’s evolutionary history, especially its shift from quadrupedalism to bipedalism. Lay summary: Spondylolysis is a relatively common vertebral pathology usually caused by a fatigue fracture. There is reason to think that it might be connected with our lineage’s evolutionary shift from walking on all fours to walking on two legs. We tested this idea by comparing human vertebrae with and without spondylolysis to the vertebrae of great apes. Our results support the hypothesis. They suggest that people who experience spondylolysis have vertebrae with what are effectively exaggerated adaptations for bipedalism

A 3D Basicranial Shape-Based Assessment of Local and Continental Northwest European Ancestry Among 5th to 9th Century CE Anglo-Saxons

The settlement of Great Britain by Germanic-speaking people from continental northwest Europe in the Early Medieval period (early 5th to mid 11th centuries CE) has long been recognised as an important event, but uncertainty remains about the number of settlers and the nature of their relationship with the preexisting inhabitants of the island. In the study reported here, we sought to shed light on these issues by using 3D shape analysis techniques to compare the cranial bases of Anglo-Saxon skeletons to those of skeletons from Great Britain that pre-date the Early Medieval period and skeletons from Denmark that date to the Iron Age. Analyses that focused on Early Anglo-Saxon skeletons indicated that between two-thirds and three-quarters of Anglo-Saxon individuals were of continental northwest Europe ancestry, while between a quarter and one-third were of local ancestry. In contrast, analyses that focused on Middle Anglo-Saxon skeletons suggested that 50–70% were of local ancestry, while 30–50% were of continental northwest Europe ancestry. Our study suggests, therefore, that ancestry in Early Medieval Britain was similar to what it is today—mixed and mutable

Mandibular shape and diet in extant primates: a 3D geometric morphometric analysis.

Establishing a link between mandibular morphology and diet in extant primates has long been a goal in biological anthropology because it should provide important insight into the diets of extinct primates, including fossil hominins. To date, efforts to explore this question have produced mixed results, largely perhaps due to a reliance on the use of 2D morphological data. Here, we report a study where we investigated whether 3D shape data would provide a clearer picture. We used geometric morphometrics to analyse 3D mandibular shape variation in a sample of > 200 primate specimens, representing individuals from 27 species and five families. Two sets of analyses investigated i) whether there was a relationship between mandibular shape and four standard dietary categories and ii) whether there was a relationship between mandibular shape and a well-known index of diet quality. We found an association between mandibular shape and the dietary categories when we employed raw Procrustes coordinates and allometry-free residuals, but the relationship was weak to non-existent when the effects of phylogeny were taken into account. We found no relationship between shape and the diet quality index, no matter whether the data were raw, corrected for the effects of allometry, corrected for the effects of phylogeny, or corrected for the effects of both allometry and phylogeny. Taken together, the results of the two sets of analyses suggest that there is a weak relationship between 3D mandibular shape and diet in extant primates. Allometry and phylogeny appear to be more important influences on the 3D shape of extant primate mandibles than is diet. We conclude from this that 3D analysis of mandibular shape is unlikely to further illuminate the diets of extinct primates, and research efforts should, therefore, be directed elsewhere

The Composition of the Founding Population of Iceland: A New Perspective From 3D Analyses of Basicranial Shape

The settlement of Iceland in the Viking Age has been the focus of much research, but the composition of the founding population remains the subject of debate. Some lines of evidence suggest that almost all the founding population were Scandinavian, while others indicate a mix of Scandinavians and people of Scottish and Irish ancestry. To explore this issue further, we used three-dimensional techniques to compare the basicrania of skeletons from archaeological sites in Iceland, Scandinavia, and the British Isles. Our analyses yielded two main results. One was that the founding population likely consisted of roughly equal numbers of Scandinavians and people from the British Isles. The other was that the immigrants who originated from the British Isles included individuals of southern British ancestry as well as individuals of Scottish and Irish ancestry. The first of these findings is consistent with the results of recent analyses of modern and ancient DNA, while the second is novel. Our study, therefore, strengthens the idea that the founding population was a mix of Scandinavians and people from the British Isles, but also raises a new possibility regarding the regions from which the settlers originated

Mixed ancestry of Europeans who settled Iceland and Greenland: 3D geometric-morphometric analyses of cranial base shape

Debate surrounds the identity of the Europeans who settled Iceland and Greenland in the early medieval period. Historical sources record settlers travelling from Norway to Iceland and then Greenland, but recent analyses of biological data suggest that some settlers had British and Irish ancestry. Here, the authors test these hypotheses with 3D-shape analyses of human crania from Scandinavia, Britain and Ireland, and one of the Norse colonies in Greenland. Results suggest that some 63 per cent of the ancestry of the Greenlandic individuals can be traced to Britain and Ireland and 37 per cent to Scandinavia. These findings add further weight to the idea that the European settlers who colonised Iceland and later Greenland were of mixed ancestry.</jats:p