Why Are Some People Left-Handed? Left-handed people have often been viewed in a negative way. In many cultures, using the left hand has been seen as clumsy, wrong, or even unlucky. In French, the word gauche means both "left" and "clumsy." In English, "left" comes from an old word meaning "weak," and the word "sinister" comes from the Latin word for "left," linking it to bad luck. While these days many places aren't as negative about being left-handed as they once were, left-handed people are still a small group. Only about 10% of the world's population uses their left hand for writing and other tasks. So why are there so few left-handed people? Scientists think it may be a mix of genetics and chance. And one particular gene responsible for protein coding might be part of the answer. In a study involving more than 350,000 people, researchers found that those with a rare version of this gene were more likely to be left-handed. Fewer than 1% of people have this version of the gene, but left-handed people were 2.7 times more likely to carry it than right-handed people. This particular gene helps build tiny structures in our cells called microtubules. Microtubules shape cells, and they're especially important when the brain is growing in the womb. Scientists believe these microtubules may affect how the brain develops, and especially how its two sides form. This matters because different sides of the brain control different things — the left side controls the right side of the body, and the right side controls the left. If one side of the brain becomes stronger during development, it could lead someone to prefer using one hand over the other. This doesn't explain all cases of left-handedness — and some scientists say that, in most cases, being left- or right-handed may actually be random. But this gene does give researchers ideas about how the brain develops, and why handedness may be different from one person to the next.