Figure 2. Examples of the development of the propagation of cleaning techniques within matrilines.

2a) rubbing grapes in hands; 2b) rubbing grapes on substrate. Only matrilines for which 2 individuals or more participated in at least 6 experiments are represented. On each panel, the mother female is represented in black, other individuals with red. The lines represent a running median smoother based on three consecutive data points (J. W. Tukey, Exploratory Data Analysis, Reading Massachusetts: Addison-Wesley, 1977). Above each panel the group name is given and the matriline's rank in the hierarchy.