Why Are More People Right-Handed Than Left-Handed?

The right half of the brain controls the left side of the body, and the left side of the brain controls the right side of the body.

In most people, the left side of the brain is better developed, so the right hand is stronger and more controllable than the left hand. But sometimes, the right side of the brain is more developed; then the person is left-handed.

Less than one person in six is left-handed. No one is sure why so many more people are right-handed. It’s possible that the reasons go back to the days of the caveman.

A person who was born right-handed would fight with a weapon in his right hand and use his left hand to shield himself; a left-handed person would fight with his left hand and shield himself with his right hand.

A person who uses his left hand to shield himself protects his heart, which is on the left side of the body. So, many right-handed persons who were wounded would survive, while left-handed persons would suffer wounds around their heart and die.

Over the course of evolution, this higher survival rate among right-handed persons could have led to more persons being born right-handed.

Comments

  1. Matt says

    The “sword-and-shield” hypothesis was debunked decades ago. In studies of countries with high rates of violence and murder, left handedness is actually more common, presumably because a left-handed person can catch someone off guard if the victim is used to fighting only right-handed people.

    The prevailing hypothesis today is that it was in the “meningitis belt” of Africa, early in human history. Meningitis is disproportionately more lethal in right-brained individuals (and thus more commonly left-handed people).

    Stats on handedness are also skewed because social stigma causes many natural left-handed people to use their right hands.

  2. Richard says

    Im right handed but many of my friends are left handed. But studies show that left handed people die nine year earlier than a right handed person. Justin bieber barack Obama and bill gates are left handed. Bill gate made right handed mouse because their is more tight handed people. I still used my left hand to twist caps open and open doors. Be glad that you got two hands rather than one!

  3. dee cee says

    I am a biologist, or was one when I graduated 30 years ago. Left or right handedness does have, off the top of my head, a genetic component. Not saying that there are not other factors during fetal development that are also significant.
    But now with wikipedia and google, everyone can know what I know in 10 minutes or less.

    For instance: “A large study of twins from 25,732 families by Medland et al. (2006) has indicated that the heritability of handedness is 24%.[14] This leaves about three quarters of the effect to be explained by environmental factors.”

    And: “Previc, after reviewing a large number of studies, found evidence that the position of the fetus the final trimester and a baby’s subsequent birth position can affect handedness.”

    Also interesting, left handed college grads make 10 to 15% more than right handed grads. Left handed people are about one and a half times more likely to die in a fatal accident and have two times the chance for a stressful delivery. Which brings us back to the postulate that there is a cause and effect going on in fetal development.

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