A new international study has suggested that humans became overwhelmingly right-handed because of two major evolutionary changes — walking upright on two legs and developing larger brains.
The research, published in the journal PLOS Biology, found that nearly 90 per cent of humans favour their right hand, unlike other primates which show only mild hand preference or remain largely ambidextrous.
Researchers analysed data from more than 2,000 individuals across 41 primate species, including humans, apes and monkeys, to understand what made human handedness unique.
Upright walking changed how humans used hands
According to the study, early human ancestors such as Australopithecus likely showed only a mild preference for one hand, similar to modern apes.
However, stronger right-handedness appeared later in species belonging to the Homo genus, including Homo erectus and Neanderthals, before reaching its peak in modern humans.
Scientists believe the shift began when early humans started walking upright, freeing their hands from movement-related tasks and allowing them to specialise in activities such as carrying objects, making tools and throwing weapons.
“When animals walk on all fours, their hands are mostly used for locomotion,” researchers explained.
Bigger brains reinforced hand preference
The study also found that growing brain size and increased left-right brain specialisation played a major role in strengthening handedness.
Researchers said human brains gradually became more specialised, improving coordination, motor control and manual dexterity.
Lead researcher Thomas Püschel from the University of Oxford said humans stand out among primates because of both strong individual hand preference and a shared population-wide bias towards the right hand.
Scientists believe handedness may have evolved as part of broader neurological and behavioural adaptations that helped humans become more skilled at tool use and complex tasks.