Why are some people left-handed?
About 10 percent of people are left-handed. Handedness is influenced by many genes as well as environmental factors before birth, and it is linked to how the brain divides tasks between its two halves.
Handedness starts to develop before birth. Ultrasound studies show that most fetuses prefer sucking their right thumb. Scientists have found dozens of genes that slightly influence handedness, but no single left-handed gene. Even identical twins can have different dominant hands.
The left side of the brain controls the right side of the body, and vice versa. In most right-handed people, language is centered in the left hemisphere. Many left-handed people also have language mainly on the left side, but they are more likely than right-handers to have it on the right or spread across both sides.
History of left-handedness
For centuries, left-handed people faced prejudice, and children were often forced to write with their right hand. The word sinister comes from the Latin for left. Today, left-handedness is widely accepted, and tools like left-handed scissors are easy to find.
Did You Know?
International Left-Handers Day is celebrated every year on August 13.
This answer is general information, not medical advice. For a personal health question, talk to a doctor.