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5h ago

Study Links Human Right-Handedness to Bipedalism and Later Brain Growth

A cross-species meta-analysis using evolutionary models attributes the human right-hand majority to walking upright followed by later brain expansion.

© Adriano Contreras / Gizmodo
Two Ancient Clues May Finally Explain Why 90% of Us Are Right-Handed
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Scientists may have finally cracked why 90% of humans are right-handed — and the answer has nothing to do with our hands, it has to do with our legs

Overview

  • The PLOS Biology paper by Püschel, Hurwitz and Venditti, published Wednesday, compiled hand-use data from 2,025 individuals across 41 monkey and ape species and tested those data with models that account for shared ancestry.
  • The authors propose a two-stage explanation: the shift to bipedalism freed the hands and created opportunities for manual specialization, and later encephalization reinforced a population-level rightward direction.
  • Modern humans stand out with an extreme right-hand bias, the study projects stronger rightward preferences in Homo ergaster/erectus and Neanderthals, and identifies Homo floresiensis as a notable exception.
  • The team tested common alternatives such as tool use, language lateralization, diet, habitat and sociality and found those factors explained population handedness less well than limb proportions tied to bipedalism and brain size.
  • Key questions remain about why about 10 percent of people are left-handed, how culture or genes maintain that minority, and how the study’s approach can refine interpretations of handedness in the fossil record.