Around 85% of humans prefer their right hand for tasks like writing and eating, a bias that is universal across all human populations. Archaeologist Natalie Uomini of the University of Liverpool notes that no left-handed majority population has ever been reported. This asymmetry, known as lateralisation, originates in the brain, where the left hemisphere controls the right side of the body.
Lateralisation may have evolved over 500 million years, allowing the brain to process routine and unexpected tasks simultaneously. For instance, fish, toads, and birds are more likely to attack prey seen with the right eye, suggesting an ancient origin. As early hominins adopted upright walking, their hands became free for tool use, potentially strengthening individual hand preferences. A study of chimpanzees found that when forced to stand upright, they showed lateral preferences, though not specifically right-handed.
Evidence from ancient stone tools indicates that right-handedness became species-wide over time. Tools from Koobi Fora, Kenya, dating to 1.5 million years ago, show signs of right-handedness in Homo habilis and Homo erectus. By around 600,000 years ago, Homo heidelbergensis clearly favoured the right hand, as shown by wear patterns on teeth suggesting food was brought to the mouth with the right hand.
The exact cause of the shift remains debated. One leading hypothesis, the Homo loquens hypothesis, links right-handedness to the evolution of language. Since language processing is primarily located in the left hemisphere—even more consistently than handedness—it is thought that as language evolved, right-hand preference intensified as a side effect. This suggests that bipedalism drove general lateralisation, while language later pushed the bias toward the right side.
