A new study suggests humans became overwhelmingly right-handed because of two major evolutionary shifts: walking on two legs and developing much larger brains. Researchers found that as human ancestors evolved, their right-hand preference steadily intensified — transforming a mild tendency into one of humanity’s most distinctive traits.

A new study suggests humans became overwhelmingly right-handed because of two major evolutionary shifts: walking on two legs and developing much larger brains. Researchers found that as human ancestors evolved, their right-hand preference steadily intensified — transforming a mild tendency into one of humanity’s most distinctive traits.