Oxford-led PLOS Biology study links human population-wide right-handedness to bipedalism and brain expansion, not culture alone.
Key Takeaways
Paper in PLOS Biology models handedness across primates; adding brain size and arm-to-leg ratio removes humans as an evolutionary outlier.
Predicted handedness gradient across hominin lineage: weak rightward bias in Ardipithecus/Australopithecus, strengthening through Homo ergaster, erectus, Neanderthals, peaking in Homo sapiens.
Homo floresiensis (small brain, mixed bipedal/climbing body) predicted to have weak handedness, consistent with the two-factor model.
Two-stage mechanism proposed: bipedalism freed hands first, creating selective pressure for lateralized manual skill; brain expansion then locked in the rightward bias.
Open questions remain: role of cumulative culture, persistence of left-handedness, and convergent limb preferences in parrots and kangaroos.
