1ICAR Project Team, LIRMM, CNRS/University Montpellier 2, France, 2AMIS Laboratory, CNRS/University of Toulouse, France, 3SHAMAN Project Team, INRIA Lille Nord Europe, France, 4Institute for Human Evolution, University of Witwatersrand, Johannesburg, South Africa
Thursday 4:00-4:15, Ballroom C
Plastic taphonomic deformation is a major problem in studying paleoanthropological fossils. In general, paleoanthropologists retrodeform the fossil manually according to the position of anatomical landmarks or based on symmetry planes. Another method is to analyse the change of shape of a simple anatomical structure as the orbit in order to compute strain parameters and infer the magnitude and orientation of the deformation. This is particularly interesting as it does not only allow one to retrodeform the fossil but it also gives information about the taphonomic process, which may be correlated with geologic measurements.
We propose to extend this method by analysing the deformation of the complete fossil. We used the open-source SOFA software framework targeted at real-time biomechanical simulation. The fossil is modelled as a linear homogeneous stiff material which is plunged into a linear homogeneous soft material which represents the surrounding geological layers. We apply a directional force on the surrounding material and simulate the 3D deformation of the virtual fossil. We compute then a quality factor which is based on the correspondence or the symmetry of deformed and non-deformed landmarks. We search for the direction and magnitude of the force which maximizes the factor quality and we get a retrodeformation force and a 3D retrodeformed version of the fossil.
We performed experiments on the highly-distorted lower face STS 52a (Australopithecus africanus). The quality factor is based on the alignment with the corresponding mandible STS 52b which is assumed weakly deformed. The results are consistent with the paleo-anthropological observations.
This research is supported by the French Center for Scientific Research (PEPS FOSSPROPALE and PICS INLOO projects).