Approximately 10% of the world population is left-handed. What causes this anomaly?While there are several theories that try to explain this trait -- such as the
positioning of the baby during the final trimester,
hormone exposure during pregnancy, or
epigenetic factors -- the most consistent and hardwired explanation boils down to plain old
genetics. In other words, the reason you're right-handed or left-handed is because it's written in your DNA.
Research suggests that handedness displays a complex inheritance pattern. For example, if both parents of a child are left-handed, there is a 26% chance of that child being left-handed. A large study of twins from 25,732 families also indicated that the heritability of handedness is roughly 24%.
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