Human handedness: an inherited evolutionary trait

Our objective was to demonstrate that human population-level, right-handedness, is not species specific, precipitated from language areas in the brain, but rather is context specific and inherited from a behavior common to both humans and great apes. In general, previous methods of assessing human handedness have neglected to consider the context of action, or employ methods suitable for direct comparison across species. We employed a bottom-up, context-sensitive method to quantitatively assess manual actions in right-handed, typically developing children during naturalistic behavior. By classifying the target to which participants directed a manual action, as animate (social partner, self) or inanimate (non-living functional objects), we found that children demonstrated a significant right-hand bias for manual actions directed towards inanimate targets, but not for manual actions directed towards animate targets. This pattern was revealed at both the group and individual levels. We used a focal video sampling, corpus data-mining approach to allow for direct comparisons with captive gorillas (Forrester et al. in Anim Cogn 14(6):903–907, 2011) and chimpanzees (Forrester et al. in Anim Cogn in press, 2012). Comparisons of handedness patters support the view that population-level, human handedness, and its origin in cerebral lateralization is not a new or human-unique characteristic. These data are consistent with the theory that human right-handedness is a trait developed through tool use that was inherited from an ancestor common to both humans and great apes.