Chimpanzee right-handedness: Internal and external validity in the assessment of hand use

In sum, I would argue that captive chimpanzees and other great apes exhibit population-level handedness. More systematic and controlled studies are needed in wild apes before any definitive statements can be made regarding the potential role of different settings on the expression of handedness. An important finding, to which the comparative method can offer some interesting insight, is the difference in distribution of handedness between apes and humans. The ratio of right- to left-handed chimpanzees is about 2: 1 or 3: 1 (in the case of gesture and throwing) which is lower than most reports of handedness in various human cultures (Raymond and Pontier, 2004). Whether this difference reflects the emergence of socio-cultural evolution or alterations in the genome between chimpanzees and humans remains unknown but warrants further investigation.