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

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 for 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 genes determine being left or right-handed.

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 its 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. 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.

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.

Some factors can likely cause hand preference, 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. While some researchers insist on genes as the primary influencer of handedness, others see environmental effects as a more realistic factor. The environmental factors in the womb and exposure to some hormones can impact the hand a person favors as they grow. 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.

Here are two other unusual factors that can likely cause hand preference:

1. 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.

2. Preference Changes

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

Tomohiro Takano
Tomohiro Takano
Co-Founder and CEO