High integration is shown between occluding upper and lower teeth in Homo sapiens, Pan troglodytes, P. gorilla and Pongo pygmaeus. With the unexplained exception of P. troglodytes, there are possible grounds for cautious acceptance of the hypothesis of higher integration between occluding parts of teeth, as would be expected after natural selection for efficient occlusion. There is wide variation in integration levels and in the relative amounts that occlusal integration exceeds nonocclusal integration.