Overview
- The peer-reviewed study, published in PLOS Biology, tested multiple theories and found that two traits best account for humans’ strong rightward bias: a shift to walking on two legs and later increases in brain size and reorganization.
- Researchers combined a meta-analysis with phylogenetic comparative models using data from 2,025 individuals across 41 monkey and ape species to control for shared evolutionary history and compare competing explanations.
- Model reconstructions project a gradual strengthening of right-hand preference through the Homo lineage — weak bias in Ardipithecus and Australopithecus rising in H. ergaster and H. erectus and peaking in H. sapiens — with Homo floresiensis as a notable outlier.
- The paper leaves key questions open: roughly 10% of people are left-handed, and the roles of rare genetic variants, prenatal brain asymmetry, and cultural forces in maintaining or amplifying left-handedness remain unresolved.
- The study’s method offers a roadmap for future work by linking anatomy and behavior across species and by encouraging tests of similar limb-preference patterns in other animals and more detailed genetic and developmental studies in humans.