Scientists from the University of Oxford believe they may have finally uncovered why the vast majority of humans are right-handed.
Across cultures worldwide, only around 10 per cent of people are naturally left-handed, a mystery that has puzzled researchers for decades.
According to the new study, the answer may lie in two major developments in human evolution — walking upright on two legs and the dramatic growth of the human brain.
Lead researcher Thomas A. Püschel described the study as the first to test several major theories about handedness within a single scientific 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,” he said.
To investigate the mystery, researchers analysed data involving 2,025 individuals across 41 species of monkeys and apes.
The team examined multiple factors believed to influence handedness, including tool use, diet, habitat, social behaviour, body size, brain size and movement patterns.
Initially, humans appeared to stand far outside the patterns observed in other primates.
However, researchers found that once brain size and the relative length of arms compared to legs were included in the analysis, humans no longer appeared evolutionarily unusual.
The findings suggest that upright walking freed the hands for activities such as tool use, communication and fine motor tasks, which may have encouraged stronger hand preference over time.
Researchers also believe the rapid growth and reorganisation of the human brain further strengthened right-handed dominance through greater hemispheric specialisation.
Using the same evolutionary model, scientists estimated the likely handedness of extinct human ancestors.
The study found that early human species such as Australopithecus and Ardipithecus probably showed only mild preferences for using the right hand.
However, stronger right-handed tendencies appeared to emerge later in species such as Homo erectus and Neanderthal.
One notable exception was Homo floresiensis, often referred to as the “hobbit” species discovered in Indonesia.
Researchers found the species showed a much weaker preference for right-handedness, likely because it had a smaller brain and relied on both upright walking and climbing.
The study proposes a two-stage evolutionary explanation for modern human handedness: first, walking upright freed the hands, and later, brain expansion reinforced specialised hand dominance.
The findings were published in the scientific journal PLOS Biology.
