Why 90% of people are right-handed: Scientists trace answer back millions of years

New research suggests that upright walking and brain development shaped humans’ right-handedness. This evolutionary process begins when the hands are freed from the task of movement. As hominins evolved, right-handedness became stronger as brain size increased. Larger brains promote specialization of the cerebral hemispheres, making consistent hand use more common. This explains why most people prefer the right hand over others.