Why are most people right-handed? Scientists link it to walking

If you walk into a café, you’ll see people sipping their morning coffee, biting into a croissant, scrolling through their phones, or flipping through a book. The odds are that almost all of them are using their right hands. It’s no surprise that about 90% of the people you meet are right-handed. But have you ever wondered why we use our right hands? No other primate species has this kind of preference. Our closest relatives, like chimpanzees, gorillas and orangutans, show individual hand preferences, but nothing like the near-universal right-handedness seen in humans.

A new Oxford-led study has finally unravelled the secret behind this right-hand preference. Interestingly, this traces back to the way we walk and to brain expansion. The findings are published in PLOS Biology.

Right-hand use and its link to walking straight

About 90% of people across every human culture use their right hand. This is an exception among primate species. For decades, researchers struggled to find the reason behind this strange puzzle. However, the new Oxford researchers found that the mystery comes down to two defining features of human evolution – walking on two legs and the dramatic expansion of the human brain.

The study, conducted by Dr Thomas A. Püschel and Rachel M. Hurwitz at Oxford’s School of Anthropology and Museum Ethnography, with Professor Chris Venditti at the University of Reading, analysed data from 2,025 individuals across 41 species of monkeys and apes. Using Bayesian modelling, they tested the major existing hypotheses for why handedness evolved. These include tool use, diet, habitat, body mass, social organisation, brain size and movement.

What they found

The findings were striking. They found that humans stood conspicuously outside the pattern that explained every other primate, until the researchers added two critical factors: brain size and bipedalism. When these factors – walking upright and developing larger brains – were considered, humans stopped looking like an evolutionary anomaly. These two factors explain why we use our right hands.

The researchers also estimated whether handedness preferences existed in extinct ancestors. What they found tells a compelling evolutionary story. Early hominins such as Ardipithecus and Australopithecus probably had only mild rightward preferences. This is broadly similar to modern great apes. But with the arrival of the genus Homo, this bias grew stronger. The use of the right hand increased from Homo ergaster, Homo erectus and Neanderthals, ultimately reaching us, Homo sapiens.

One exception

And yet, there is one exception – Homo floresiensis, the small-brained ‘hobbit’ species from Indonesia. It showed a weaker predicted preference. The researchers think this exception aligns perfectly with their broader findings: Homo floresiensis had a small brain and a body adapted to a mix of upright walking and climbing, rather than full bipedalism.

According to the researchers, the evidence points to a two-stage evolutionary narrative. First, walking upright came, freeing the hands from the work of movement and creating new selective pressure for fine, lateralised manual behaviours. Larger brains came later. As they grew and reorganised, the rightward bias strengthened and became a near-universal pattern seen today.

“This is the first study to test several of the major hypotheses for human handedness in a single framework. Our results suggest it is probably tied to some of the key features that make us human, especially walking upright and the evolution of larger brains. By looking across many primate species, we can begin to understand which aspects of handedness are ancient and shared, and which are uniquely human,” Dr Thomas A. Püschel, Wendy James Associate Professor in Evolutionary Anthropology at the University of Oxford, said in a statement.

The study opens new avenues for future research, including the role of human culture in reinforcing right-handedness, why left-handedness exists at all, and whether there are similar limb preferences in other animals, pointing to a convergent story.