The shape of wrist bones (carpals) in living hominids are thought to be adapted to the primary function of the hand, which in Homo sapiens is for manipulation, and in non-human hominids, locomotion. However, the hominid hand is inherently versatile in its use, and parsimony would suggest that the hominid last common ancestor was capable of manipulating and using simple tools. Therefore, key questions in palaeoanthropology ask when, why, and how tool use moved from facultative, as it is in other

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... hominids, to obligate, as it is in H. sapiens. Inferring this transition within the fossil record is challenging as habitual behaviours are not always reflected in the external morphology of the skeleton. As the internal microstructure of bone is known to adapt to load dynamically, bone functional adaptation analyses provide an avenue to investigate how a joint has actually been loaded over an individual's lifetime. The central question asked by this thesis was: 'How and why does the internal structure of wrist bones differ among extant and extinct hominids?'. To achieve this aim, I investigated 1) whether functionally meaningful differences exist in the microarchitecture of extant hominid carpals; 2) how to detect signals of functional adaptation within the complex biomechanical environment of the wrist; 3) what can be inferred about hand use from the proximal capitate bone of fossil hominins? This thesis undertook three research projects, which all use 'whole-bone' methodologies for investigating functional signals of hand use. Using micro-computed tomography, I quantified and compared trabecular and cortical bone microarchitecture in 264 individual carpal bones across four extant hominids (Pongo, Gorilla, Pan, and H. sapiens) and four extinct hominins (Australopithecus sediba, Homo naledi, Homo floresiensis and Neanderthals). In the first project, I used inter- and intraspecific analyses to compare the trabecular and cortical microstructure of the proximal and distal capitate in extant hominids. Unique combinations of m [...]