Recent research from the University of Oxford and the University of Reading reveals that bipedalism and increased brain size are key factors contributing to the notable predominance of right-handedness in humans.
Reconstruction of Homo erectus.
According to Thomas Püschel, a researcher at the University of Oxford, “Approximately 90% of individuals globally show a preference for using their right hand.”
“Some researchers propose that this trend has existed since the Neolithic period, while others suggest it has been constant throughout human history,” he adds.
The research highlights that the pronounced lateralization of hand use in humans results in rare occurrences of ambiguous hand preferences or forms of ambidexterity, a stark contrast to findings in other primate species.
Despite some level of hand lateralization in certain primate groups, the consistent handedness seen in humans stands out as a remarkable evolutionary phenomenon that remains largely unexplained.
The study analyzed data from 2,025 individuals representing 41 different monkey and ape species.
Employing Bayesian modeling, the researchers explored evolutionary relationships across species to examine existing hypotheses regarding handedness evolution, including aspects like tool use, diet, habitat, body weight, social structures, brain size, and locomotion.
Interestingly, humans deviated from typical primate patterns, a difference that disappeared when brain size and the relative limb lengths—key indicators of bipedalism—were involved in the model.
Essentially, the upright walking and larger brains of humans clarify our evolution and no longer categorize us as anomalies.
The researchers also estimated the likely handedness of our extinct ancestors, indicating a gradual shift: Ardipithecus and Australopithecus likely exhibited a mild right-handed preference akin to modern great apes.
However, the emergence of the Homo genus, including species such as Homo ergaster, Homo erectus, and Neanderthals, marked a significant increase in right-handedness, peaking in modern Homo sapiens.
A notable exception is Homo floresiensis, a small-brained species from Indonesia, which exhibited a much weaker handedness tendency, aligning with their unique adaptations for a mix of bipedalism and climbing.
The research team posits a two-step evolutionary narrative.
Initially, upright walking liberated human hands from locomotion tasks, introducing new selective pressures for fine manual movements.
As larger brains developed and reorganized, the inclination toward right-handedness strengthened, resulting in the nearly universal pattern observed today.
“This groundbreaking study is the first to assess several major hypotheses concerning human handedness within a unified framework,” remarked Dr. Püschel.
“Our findings indicate that our distinct handedness is likely connected to the evolution of crucial human traits, particularly bipedalism and larger brain size.”
“By examining multiple primate species, we can distinguish which aspects of handedness have remained consistent over time versus those that are unique to humans.”
For the full study, refer to the article published in PLoS Biology here.
_____
Püschel, T. et al. 2026. Bipedalism and brain enlargement explain human handedness. PLoS Biol 24 (4): e3003771; doi: 10.1371/journal.pbio.3003771
Source: www.sci.news
