The co-evolution of human hands and tool using behaviour

点击翻译按钮获取中文摘要

When you talk to people about what makes humans different from other animals, one of the features that they will rapidly identify is the human hand. Indeed they are very likely to identify the 'opposable thumb' as a uniquely human characteristic. Whilst it can be argued that this is not strictly true, it is certainly the case that there are no other animals that have anything like the degree of precise control of their hands that humans have. We take for granted the fine movements of individual fingers that allow us to play the piano or tie our shoelaces, and these are activities that are impossible for non-humans to achieve. It is likely that the evolutionary history of our species is very closely linked to the evolutionary history of our hands and this is therefore an important area for scientific study. We currently know a great deal about how the shape of our hands has changed from those of closely related species but we actually know very little about how these shape changes are linked to how the hand functions. The story of our divergence from the common ancestor of chimpanzees and modern humans includes walking on our hindlimbs, the creation of stone tools, the increase in our intelligence, and living in extended social groups. The change in function of the human hand by losing its locomotor role and allowing its specialisation for manipulating and sensing the world, and extending its role in communication becomes a compelling narrative. In particular the idea that the evolution of our hands is closely linked to our adoption of increasingly sophisticated tools seems extremely plausible.Thus the aim of this research project is to explore the changes in functional capabilities of the human hand and to use this information to evaluate the evolutionary history of the hand and its relationship to tool use and manufacture. To achieve this goal we need to collect information about how the individual parts of the hand are used in humans. This needs to be done in a controlled fashion so that we can make objective comparisons of the mechanical requirements of different actions that we can link to specific artifacts in the achaeological record. We therefore propose to collect movement and force information from humans whilst performing such a range of tasks. We will use a range of exciting new technologies developed for virtual reality and movie special effects where hand and finger movements can be recorded automatically using specially instrumented gloves and by attaching reflective markers to the fingers. In addition simply recording this information is insufficient to fully understand a mechanism as complex as a hand. We will also construct 3D computer simulations of these hand and arm movements using information from medical imaging and dissections. We will then use a variety of sophisticated mechanical engineering techniques to evaluate how the individual bones and muscles function within the hand. We also need to evaluate how human hand function has changed over time and this means that we need to investigate the hands of fossil primates as well as their living relatives. To do this we will create equivalent computer simulations for these extinct species reconstructed from the fossil bones. The computer models will allow us to predict the capabilities of these species and we will be able to directly evaluate the changes in locomotor, foraging and tool use capabilities of the hands of our closest ancestors over time.