December 7, 2021

Can your Genes Determine If You’re Left or Right-Handed?

Hand preference or handedness is the ability to be more skilled with one hand
Tomohiro Takano

Can Your Genes Determine if You’re Left or Right-Handed?

For over 150 years, scientists have studied the brain’s functions and how it influences a person’s preference between being left and right-handed. However, they still couldn’t reach a compromise on why a significant percentage of the population is left-handed.

Before left-handedness became more accepted, some cultures in the past have revealed naturally left-handed children being forced to switch to their right hand. This is probably due to most tools built for right-hand handling or the assumed awkwardness of left-hand writing. The controversies around this thought have resulted in people wondering if right-handed and left-handed genetics are real.

Until recently, scientific studies have uncovered the first genetic instructions associated with determining why people are left or right-handed. While this discovery potentially offers a different insight into the structure and function of the human brain, it also shows how genetics play a vital role in the hand of a personal favor.

The Truth About Being Left And Right-Handed  

Hand preference or handedness is the ability to be more skilled with one hand and use it more comfortably than the other for specific tasks, such as writing, throwing a ball, or handling a tool. Even though the percentage of people specified with particular hand preferences varies by culture, about 10 to 15 percent of Western countries are right-handed, while 85-90 percent are left-handed.

There are uncommon cases within these sets of people, some mixed-handed, meaning they prefer to perform different tasks with either hand or ambidextrousness and use both hands equally well for functions.

The development of handedness begins before birth. Often, babies use both hands equally, but their hand preferences become increasingly apparent and consistent as they grow. However, there is not yet enough information on its biological influences.

One inevitable aspect of hand preference is how it relates to the brain’s hemispheres, such that it's part of the development process between the right and left sides of the body. This way, the left hemisphere controls the movements of the right side of the body and the right hemisphere.

How Your Genes Influence Your Handedness

Researches on human hand preferences have shown that the source of handedness is biological and even genetic. But the initial thought of a single gene controlling handedness became invalid when researchers found studies suggesting that multiple genes contribute to this trait. 

Each one contributes a weak effect in establishing hand preference. However, right from the earliest stages of development, these genes play a more significant role in determining the overall right-left asymmetry of the body.

Identifying these genes has been another task for researchers; only a few are known.  For instance, people with a psychiatric disorder, schizophrenia, are increasingly likely to have the right-handed PCSK6 gene. Also, people with a condition causing difficulties with spelling and reading – dyslexia have an increasing chance of association with the left-handed LRRTM1 gene or left-hand genetics. It’s not an assurance that these genes would relate to a person’s handedness without these conditions.

Development Of Preferred Handedness

Handedness is another complex trait with no simple pattern of inheritance. Children of left-handed parents may likely have more chances to be left-handed than children of right-handed parents. But since the general possibility of being left-handed is relatively low, most children of left-handed parents often turn out to be right-handed.

Identical twins should have more chances than non-identical twins or other siblings to both have one preference between being left and right-handed. In many cases, twins are oppositely handed.

With the absence of a definite genetic factor backing handedness, it’s believed that hand preferences are still more of a matter of choice and learning than anything else. Since genetic factors associated with handedness show a relatively weak and subtle connection, there are reasons for future studies.

Although some conclusions are being made that even if there are future identification of genes related to handedness in the future, it’s unlikely that analysis of human DNA can predict handedness.

7 Factors That Can Likely Cause Hand Preference

There remains a mystery why only an average of one in ten people favor their left hand. Two left-handed parents producing right-handed children still show a weak direct genetic link to handedness.

Some theories that separate between being left-handed and right-handed can depend on multiple conditions, including prenatal environment, chance, cultural influence, or even random variation among humans.

1. Genes

Some factors can likely cause, such as, genetic factors which can influence a child’s hand preference. Yet, there is no profound confirmation of this theory. A single gene from parents can be why a child favors the right hand.

In other cases, they can inherit a version of genes that influences them to be left-handed. It can also depend on reinforcement or other environmental factors. But with recent discoveries, it’s more accurate to say that the combination of minor influences of genes determines the hand preference. 

2. Environment (Modeling)

While some researchers insist on genes as the primary influencer of handedness, others see environmental effects as a more realistic factor. Speaking of birth, children are more prone to learning from what they see. Most things they start to exhibit as they grow are those they observe from their parents. However, modeling parents may not be entirely reasonable for hand preference, and it’s impossible to pass on this factor.

4. Fetal Development

The environmental factors in the womb and exposure to some hormones can impact the hand a person favors as they grow.

5. Sex

Slightly fewer girls than boys are left-dominant. This statistic leads some researchers to believe that left-hand genetics may be related to the male hormone testosterone.

6. Brain Impairment

Quite a small percentage of researchers believe that all humans are supposed to be right-handed. However, even though there is no hard evidence to support this, some theories point out that being left-handed results in certain types of brain injury in their early years.

7. Preference Changes

Another cause of hand preference is the adjustments they make early enough or due to certain conditions. Some right-handed people have been forced to shift their choice to their left hands due to injuries or illnesses.

Is Left-Handedness Bad?

There was once a time when left-handed children were forced to learn right-hand dominance. The bias against left-handedness may have begun in ancient Rome, where superstitions linked the left hand with evil doing. During the Middle Ages, left-handed people were accused of associating with the devil and were at risk of being burned at the stake. 

With such extreme prejudice against being left-handed, it’s no wonder being left-dominant was discouraged. Unfortunately, ancient peoples had no way of knowing about left-handed genetics and the role biology plays in hand dominance. 

The Challenges of Being Left-Handed

Whether the hand you use is the result of left-handed genetics, living in a world made for right-dominant people isn’t always easy. Left-handed people must learn to deal with practical problems on an everyday basis. 


Learning to write in Western cultures can be frustrating for left-handed people. Western languages are read and written from left to right, making it difficult to move the left hand across a freshly written page without smearing the ink or pencil lead. Fortunately, more students and workplaces are using laptops and other electronic devices that limit the need for handwriting documents. 

Tool Use

Most tools, from power tools to scissors, are made with right-dominant people in mind. This makes sense. After all, about 90% of people in the U.S. are right-handed. In many cases, this equates to a minor inconvenience, but in other cases, a lack of left-handed tools can make some activities dangerous. Imagine trying to use a circular saw with your left hand. 

Learning Difficulties

Some studies suggest learning difficulties like autism and epilepsy are more common in people who are left-hand dominant. Left-handed children were at once more likely to be incorrectly diagnosed with dyslexia because of their natural inclination to write from back to front — also called “mirror writing.”

The incorrect diagnosis of learning differences can create social and academic obstacles and prevent the correct diagnosis of other issues. 

Everything’s Backwards

Having to turn your coffee cup awkwardly to see the graphics or artwork on it isn’t a life crisis, but when you’re left-handed, small inconveniences add up. From safety rails on a stairway to sitting at a dining table in the middle of right-handed friends, left-handedness requires extra thought and extra steps to navigate even the simplest of daily tasks. 

The Advantages of Being Left-Handed

Not everything about left-handedness is a disadvantage. Being left-handed in a right-dominant world also has some benefits. 

Sports Performance

Leading with your left is a definite advantage in some athletic endeavors. Left-handed people are overrepresented in boxing and martial arts, and they enjoy a higher percentage of wins than their right-handed competitors. Other professional sports where left-handedness provides the upper hand include table tennis, fencing, cricket, and baseball. 

Part of the explanation may be that right-handed athletes have less experience playing against those that are left-handed, leaving them at a disadvantage. 

Mathematical Ability

Left-handed people outperform right-handed in advanced problem-solving. A study by European universities found there was no discernible difference in simple arithmetic skills when it came to handedness, but in difficult mathematics, left-handers did better. 


If your left-handed friend seems to remember things better than you do, it may not be a mere coincidence. Researchers from the University of Toledo in Ohio concluded that left-handed people are more skilled at recalling events. The theory is that the two brain hemispheres of left-handed people communicate better with one another than the brain hemispheres of right-handed people. 

Nature and Nurture Influence Handedness

Right-handed and left-handed genetics play an interesting role in human development. Left-handed people have faced social rejection in the past, and everyday tasks may be more difficult to perform, but being left-handed also comes with benefits. 

Not enough information is yet known about the biological basis for left-handed genetics. Scientists understand that which hand you hold your fork with is influenced by a complex collection of factors, including genetics, environment, sex, and personal preference. 


Tomohiro Takano
Tomohiro Takano
Co-Founder and CEO