Differences between chimpanzees (Pan troglodytes) and humans (Homo sapiens) in the resting state of the index finger: implications for pointing.

Pointing with the index finger is a universal human (Homo sapiens) behavior found in cultures around the world. The emergence of pointing in infancy has traditionally been linked with the early development of cognitive capacities such as perspective-taking, intersubjectivity, and empathy. In contrast to humans, chimpanzees (Pan troglodytes) do not develop a pointing gesture with the index finger and rarely point by gesturing with hands or arms. However, recent experimental data suggest that chimpanzees may develop cognitive skills related to perspective-taking and empathy. In this article we report the existence of a difference in the resting morphology of the index finger in humans and chimpanzees. We speculate on how this species difference may be related to species differences in pointing with the index finger.