Figure 5.

Kinetic energy values at the time of contact of the hammer with the nut for chimpanzees and humans when they crack nuts of two different species (different hardness) with hammers of different weights. For the chimpanzees, values are given for each chimpanzee. For humans, data are averaged for each age group, children from 5–6 years (G1) to 11–12 years (G4) and adults (AD; adapted from Bril et al. [32] and Foucart [64]).