more detailed comparative and developmental studies. First, we address the question of what kind of behavioral patterns may have been present in the last common ancestor of Pan and Homo. This is a crucial question if we wish to reconstruct the behavior and ecology of early hominids such as the australopithecines, because they may have had similar patterns. T. Nishida et al., Chimpanzee Behavior in the Wild: An Audio-Visual Encyclopedia, DOI 10.1007/978-4-431-53895-0 2, Springer 2010 7 8 Introduction Second, it is often said that among animals only human beings depend much more on learning than on instinct. However, the extent to which chimpanzees depend on learning, especially social learning, is not well understood. A simple behavioral pattern such as social scratch not only is absent at some sites