Being left-handed can start before you are even born. The first clues show up long before your first pencil.
When does it start?
In the womb, babies already prefer sucking one thumb. Years later, most of them write with that same hand.
Is it in your genes?
Genes play a part, but they explain only about a quarter of it. There is no single lefty gene, just many tiny nudges. Even identical twins with the same genes can use different hands.
Why were lefties rare?
About 100 years ago, left-handed kids were often pushed to use their right. Since that pressure faded, lefties have become about three times as common.
Are animals lefties too?
And humans are not the only lefties. Most wild kangaroos use their left paw to eat and groom.
Sources
- Psychology Today: Does left-handedness develop before or after birth?
- ScienceAlert: Science can predict left-handed people before they are born
- NPR (via VPM): Genes play a very small role in left-handedness
- Medical Republic: No single gene governs left-handedness
- Washington State Twin Registry: Hand preference
- University of St Andrews: Handedness in twins, meta-analyses
- UCL News: Left-handers on roll as numbers triple
- Live Science: Number of Lefties Bounces Back
- National Geographic: Kangaroos are lefties
- The Naked Scientists: Kangaroos are left handed
