PhD project: Skeletal form and function of the primate hand
Chris Dunmore is studying the trabecular and cortical structure in living and fossil primate hand bones in order to elucidate two of the most fundamental questions in our evolutionary history: when did we leave the arboreal environment; and when did we begin to create and use tools? These questions continue to be debated, in part, because of disagreements in how to interpret skeletal evidence for climbing in our fossil ancestors. Some researchers interpret this morphology as phylogenetically primitive retentions, while others see it as a functional signal of arboreality in these hominins associated with a gradual transition from the trees to obligate bipedalism. Relatively recent advances in imaging methods have allowed researchers to study the inner architecture of these bones in extant primates and fossil hominins to provide a functional signal of what our individual ancestors were actually doing during their lives. Chris’s research is focused on linking variation in hand bone structure to locomotory behaviours in extant apes, and subsequently using this information to infer how fossil hominins were actually using their hands for locomotion and/or tool manufacture and manipulation.
Prior to arriving at the University of Kent, Chris completed his undergraduate degree at the University of Cambridge and his Master’s degree at University College London. His undergraduate dissertation focused on the application of a developmental model of molar development to fossil hominin species, and his Master’s dissertation examined modularity and integration of the primate cranial base and implications for convergently brachycephalic Homo and Paranthropus.
European Research Council (ERC) Funding as part of: GRASP Evolution of the human hand: Grasping trees and tools
Synek, A., Dunmore, C., Kivell, T., Skinner, M. and Pahr, D. (2019). Inverse remodelling algorithm identifies habitual manual activities of primates based on metacarpal bone architecture. Biomechanics and Modeling in Mechanobiology [Online] 18:399-410. Available at: https://doi.org/10.1007/s10237-018-1091-y.Previously, a micro-finite element (micro-FE)-based inverse remodelling method was presented in the literature that reconstructs the loading history of a bone based on its architecture alone. Despite promising preliminary results, it remains unclear whether this method is sensitive enough to detect differences of bone loading related to pathologies or habitual activities. The goal of this study was to test the sensitivity of the inverse remodelling method by predicting joint loading histories of metacarpal bones of species with similar anatomy but clearly distinct habitual hand use. Three groups of habitual hand use were defined using the most representative primate species: manipulation (human), suspensory locomotion (orangutan), and knuckle-walking locomotion (bonobo, chimpanzee, gorilla). Nine to ten micro-computed tomography scans of each species ( n=48 in total) were used to create micro-FE models of the metacarpal head region. The most probable joint loading history was predicted by optimally scaling six load cases representing joint postures ranging from −75∘ (extension) to +75∘ (flexion). Predicted mean joint load directions were significantly different between knuckle-walking and non-knuckle-walking groups ( p<0.05 ) and in line with expected primary hand postures. Mean joint load magnitudes tended to be larger in species using their hands for locomotion compared to species using them for manipulation. In conclusion, this study shows that the micro-FE-based inverse remodelling method is sensitive enough to detect differences of joint loading related to habitual manual activities of primates and might, therefore, be useful for palaeoanthropologists to reconstruct the behaviour of extinct species and for biomedical applications such as detecting pathological joint loading.
Dunmore, C., Kivell, T., Bardo, A. and Skinner, M. (2019). Metacarpal trabecular bone varies with distinct hand-positions used in hominid locomotion. Journal of Anatomy [Online]. Available at: https://doi.org/10.1111/joa.12966.Trabecular bone remodels during life in response to loading and thus should, at least in part, reflect potential variation in the magnitude, frequency and direction of joint loading across different hominid species. Here we analyse the trabecular structure across all non-pollical metacarpal distal heads (Mc2-5) in extant great apes, expanding on previous volume of interest and whole-epiphysis analyses that have largely focussed on only the first or third metacarpal. Specifically, we employ both a univariate statistical mapping and a multivariate approach to test for both inter-ray and interspecific differences in relative trabecular bone volume fraction (RBV/TV) and degree of anisotropy (DA) in Mc2-5 subchondral trabecular bone. Results demonstrate that while DA values only separate Pongo from African apes (Pan troglodytes, Pan paniscus, Gorilla gorilla), RBV/TV distribution varies with the predicted loading of the metacarpophalangeal (McP) joints during locomotor behaviours in each species. Gorilla exhibits a relatively dorsal distribution of RBV/TV consistent with habitual hyper-extension of the McP joints during knuckle-walking, whereas Pongo has a palmar distribution consistent with flexed McP joints used to grasp arboreal substrates. Both Pan species possess a disto-dorsal distribution of RBV/TV, compatible with multiple hand postures associated with a more varied locomotor regime. Further inter-ray comparisons reveal RBV/TV patterns consistent with varied knuckle-walking postures in Pan species in contrast to higher RBV/TV values toward the midline of the hand in Mc2 and Mc5 of Gorilla, consistent with habitual palm-back knuckle-walking. These patterns of trabecular bone distribution and structure reflect different behavioural signals that could be useful for determining the behaviours of fossil hominins.
Dunmore, C., Patemen, B. and Key, A. (2018). A citation network analysis of lithic microwear research. Journal of Archaeological Science [Online] 91:33-42. Available at: https://doi.org/10.1016/j.jas.2018.01.006.The introduction of lithic microwear research into the wider archaeological community by Keeley (1980) was concurrent with the development of the processual paradigm and the adoption of the scientific method. Subsequently, lithic microwear research has benefited from over 35 years of innovation, including the introduction of novel methodological and analytical procedures. The present study employs a citation network to objectively analyse the development of microwear research. Given developments in technology, as well as the institutional isolation of early microwear research, the present analysis considers the citation network that stems from Keeley's seminal 1980 volume. The 363 papers identified as having cited Keeley (1980) in the subsequent 35 years were treated as individual nodes within the citation network. Before analysis, nodes were assigned attributes, including the type of research published and whether they were supportive of three key aspects of Keeley's experimental program: the ability to determine the function of the tool and to ascertain the type of worked material from microwear, as well as the use of high-powered microscopy techniques. Emergent properties of the papers, including closeness centrality, indegree and betweenness centrality, are used to test for significant differences between paper attributes. Similarly a clustering algorithm is used to objectively define distinct clusters of important papers within the discipline. Results indicate that a small number of nodes in the network maintain statistically significant influence on the form of the citation network. These important nodes and the distinct ‘schools of thought’ identified are discussed in the context of Keeley's initial contribution to the sub-field.
Dunmore, C., Wollny, G. and Skinner, M. (2018). MIA-clustering: a novel method for segmentation of paleontological material. PeerJ [Online]. Available at: http://dx.doi.org/10.7717/peerj.4374.Paleontological research increasingly uses high-resolution micro-computed
tomography (mCT) to study the inner architecture of modern and fossil bone
material to answer important questions regarding vertebrate evolution. This nondestructive
method allows for the measurement of otherwise inaccessible
morphology. Digital measurement is predicated on the accurate segmentation of
modern or fossilized bone from other structures imaged in mCT scans, as errors in
segmentation can result in inaccurate calculations of structural parameters. Several
approaches to image segmentation have been proposed with varying degrees of
automation, ranging from completely manual segmentation, to the selection
of input parameters required for computational algorithms. Many of these
segmentation algorithms provide speed and reproducibility at the cost of flexibility
that manual segmentation provides. In particular, the segmentation of modern and
fossil bone in the presence of materials such as desiccated soft tissue, soil matrix
or precipitated crystalline material can be difficult. Here we present a free opensource
segmentation algorithm application capable of segmenting modern and fossil
bone, which also reduces subjective user decisions to a minimum. We compare
the effectiveness of this algorithm with another leading method by using both
to measure the parameters of a known dimension reference object, as well as to
segment an example problematic fossil scan. The results demonstrate that the
medical image analysis-clustering method produces accurate segmentations and
offers more flexibility than those of equivalent precision. Its free availability,
flexibility to deal with non-bone inclusions and limited need for user input give it
broad applicability in anthropological, anatomical, and paleontological contexts.
Key, A. and Dunmore, C. (2018). Manual restrictions on Palaeolithic technological behaviours. PeerJ [Online] 6:e5399. Available at: http://dx.doi.org/10.7717/peerj.5399.The causes of technological innovation in the Palaeolithic archaeological record are central to understanding Plio-Pleistocene hominin behaviour and temporal trends in artefact variation. Palaeolithic archaeologists frequently investigate the Oldowan-Acheulean transition and technological developments during the subsequent million years of the Acheulean technocomplex. Here, we approach the question of why innovative stone tool production techniques occur in the Lower Palaeolithic archaeological record from an experimental biomechanical and evolutionary perspective. Nine experienced flintknappers reproduced Oldowan flake tools, ‘early Acheulean’ handaxes, and ‘late Acheulean’ handaxes while pressure data were collected from their non-dominant (core-holding) hands. For each flake removal or platform preparation event performed, the percussor used, the stage of reduction, the core securing technique utilised, and the relative success of flake removals were recorded. Results indicate that more heavily reduced, intensively shaped handaxes with greater volumetric controls do not necessarily require significantly greater manual pressure than Oldowan flake tools or earlier ‘rougher’ handaxe forms. Platform preparation events do, however, require significantly greater pressure relative to either soft or hard hammer flake detachments. No significant relationships were identified between flaking success and pressure variation. Our results suggest that the preparation of flake platforms, a technological behaviour associated with the production of late Acheulean handaxes, could plausibly have been restricted prior to the emergence of more forceful precision-manipulative capabilities than those required for earlier lithic technologies.
Key, A., Dunmore, C., Hatala, K. and Williams-Hatala, E. (2017). Flake morphology as a record of manual pressure during stone tool production. Journal of Archaeological Science: Reports [Online] 12:43-53. Available at: http://dx.doi.org/10.1016/j.jasrep.2017.01.023.Relative to the hominin fossil record there is an abundance of lithic artefacts within Pleistocene sequences. Therefore, stone tools offer an important source of information regarding hominin behaviour and evolution. Here we report on the potential of Oldowan and Acheulean flake artefacts to provide a record of the biomechanical demands placed on the hominin hand during Lower Palaeolithic stone tool production sequences. Specifically, we examine whether the morphometric attributes of stone flakes, removed via hard hammer percussion, preserve correlates of the pressures experienced across the dominant hand of knappers. Results show that although significant and positive relationships exist between flake metrics and manual pressure, these relationships vary significantly between subjects. Indeed, we identify two biomechanically distinct strategies employed by knappers; those that alter their hammerstone grip pressure in relation to flake size and mass and those who consistently exert relatively high manual pressures. All individuals experience relatively high gripping pressure when detaching particularly large flakes. Amongst other results, our data indicate that the distinctive large flake technology associated with the Acheulean techno-complex may be demonstrative of an ability to withstand, and by extension, to exert higher manual pressures. However inferences from smaller flake artefacts, especially, must be treated with caution due to the variable biomechanical strategies employed.
Conference or workshop item
Dunmore, C., Kivell, T., Pahr, D. and Skinner, M. (2017). Trabecular morphology across the hominoid metacarpus reflects distinct locomotor strategies. In: European Society for the Study of Human Evolution.