sources for the behavioral patterns. This time videotapes that add up to more than 1,500 h since 1999 were played back and watched again and again. This procedure has brought a qualitatively, as well as quantitatively, higher level of data scrutiny than before. Second, the multi-authored article that was published simultaneously with our last paper in 1999 provided fruitful discussion with many colleagues from different research sites directly or via email and alerted us to subtle differences in behavioral patterns. Third, and most important, the behavioral flexibility of chimpanzees is responsible for major revision of this paper. A comprehensive dictionary of human actions would amount to several thousand pages because human behavior is flexible and variable. If we take the number of chimpanzees we have intimately observed only