Why Are Some People Left-handed?

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About 10% of the population is left-handed. For the left-handed people of the world, life isn’t easy. Everyday objects of use such as desks, spiral notebooks, scissors, rulers…are a constant battle to use. Lefties have been labeled as evil in the past. Many parents force children to use their “proper” hand if they watch their child use their left hand.

The “proper” meaning- their right hand, which is viewed as the “correct” hand. However, the world has gotten progressively more accepting of left-handed folk. Luckily, there are now more manufacturers who make special left-handed versions of many items. 

Why are some people left-handed?

Some theories suggest that our preference for being left or right-handed can be predicted even before birth based on the fetus’s position in the womb. 


Researchers who study human hand preference agree that the side of the preferred hand (right versus left) is produced by biological and, most likely, genetic causes. Evolutionary natural selection produced a majority of individuals with speech and language control in the left hemisphere of the brain. Because the left hemisphere also controls the movements of the right hand–and notably the movements needed to produce written language–millennia of evolutionary development resulted in a population of humans that is biased genetically toward individuals with left hemisphere speech/language and right-hand preference. Approximately 90 percent of people are right-handed. 

Spinal Cord: 

Arm and hand movements start in the brain, in an area called the motor cortex, which sends a signal to the spinal cord. This is where the signal is translated into a motion. While the baby is growing in the womb, up until about 15 weeks, the motor cortex and the spinal cord are not yet connected, but right or left-handedness is already decided. In other words, the baby can already make movements and has chosen its favorite hand before the brain starts controlling the body. This led the neuroscience psychology researchers to believe the spinal cord is the decider for the hand preference.

Evolutionary perspective. 

Right-handed people account for 90% of the population. What caused our extreme bias toward right-handedness to evolve and persist? From an evolutionary perspective, if right-handedness evolved because it had some kind of advantage, then you might expect left-handers to disappear completely, there are some disadvantages to being left-handed, such as higher frequencies of work accidents. But there’s a leading theory to explain why left-handers have maintained a constant minority: the fighting hypothesis. 

“The idea is that in hand-to-hand combat, or in combat with weapons, there is an evolutionary advantage to being a minority left-hander,” “If you’re left-handed, you have a surprise advantage because most people are used to fighting against right-handers.” If that hypothesis is correct, it would mean that even though the downsides to left-handedness were significant enough to keep lefties in the minority, lefties’ advantage in combat at least gave them a fighting chance against eventual extinction.

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Humans are an interesting species, we don’t have all the answers yet but the key is to stay curious.

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Ritika Matta
Ritika Matta
This is Ritika Matta, I’m a Counseling Psychologist and a writer. I am passionate about spreading mental health awareness and do the same through my work which is reflected in my blogs and articles.

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