Did you know that just 10% of the population is left-handed? Scientists don't know why some people are lefties. Genetics seems to be responsible about 25% of the time, but even identical twins who share the same genes can sometimes have differing dominant hands. People believe left-handedness can affect many things your performance in school, your skills at sports, and even how much money you make. There are plenty of theories about what determines which hand you write with, but a growing number of experts believe it's random. Mixed-handers (people who use both hands equally) appear to be more different from people who favor one hand over the other. In comparison, the differences between righties and lefties are minimal. Which of the statements restates the main idea of the passage?