Overview
- The PLOS Biology paper, published Monday, links humans’ strong right-hand bias to upright walking plus larger brains using Bayesian comparisons across 41 primate species.
- In the models, humans no longer looked exceptional after adding brain size and the intermembral index, a standard arm-to-leg ratio used to gauge bipedal movement.
- The authors describe a two-stage path in which upright walking freed the hands for asymmetric tasks, then brain expansion strengthened rightward control through greater hemispheric specialization.
- Using fossil proxies for limb proportions and endocranial volume, the team infers a gradual rise in right bias across the genus Homo with a weaker pattern in Homo floresiensis.
- Open questions include why a left-handed minority persists and how culture may have reinforced right-hand norms, which the authors identify as priorities for follow-up research.