Why only 10% of people are left-handed? So far, this is what scientists know
Which side do you lean toward? No, we’re not talking about politics. We’re talking about being left-handed. And if you don’t have a lot of left-handed friends, you may have noticed how uncommon they are. So why isn’t everyone left-handed?
Even though no one has been able to explain this for sure, there are many theories that have been building up for more than a century, and the evidence points to some kind of genetic influence. Why? Because the number of left-handed people is about the same everywhere on the globe.
Those of you who regularly kick a ball know that the body isn’t perfectly balanced. When you go to kick, you’ll probably choose one foot over the other.
Hannah Fry of BBC Future says that these differences can be found in our feet, ears, eyes, and even the way our brains are set up.
If you hold your thumb out in front of you and look at it with one eye and then the other, the stronger eye is the one that seems to show the thumb closest to you. In the same way, you probably answer the phone or listen behind closed doors with the ear that you hear best with.
But why aren’t there about as many left-handed people as right-handed people?
Some experts think that social cooperation over thousands of years has made the right side of the political spectrum more powerful. In other words, when communities work together to share tools and places to live, it’s good for everyone to play with the same hand.
Others think it has to do with how the brain is split into two halves, with the left half controlling the right side of the body and the right half controlling the left side.
People think that since most people’s language and fine motor skills are controlled by the left side of their brains, this means that the right hand is also more dominant.
Alasdair Wilkins wrote in 2011 for io9 that one of the more unusual theories about why left-handedness is rare is that a genetic mutation in our distant past caused the language centers of the human brain to move to the left hemisphere, making right-handedness the norm.
And even though genes probably play a big role in deciding which hand you use, that’s probably not the whole story. Left-handed parents are more likely to have left-handed kids than right-handed parents, and this can be seen even in the womb. However, left-handed parents still have more right-handed kids overall.
Researchers have had a hard time figuring out which genes make it more likely that a person is a lefty.
In 2019, a study of 400,000 individual records found the first genetic regions linked to being left- or right-handed. There were four of them. But other research suggests that there are probably dozens of genes that affect whether we write with our left or right hand.
On top of that, other studies have found links between left- and right-handedness and things like oestrogen levels and where you were born.
In short, it seems like there are a lot of things to think about, and researchers are having trouble putting them all together. That means we don’t know for sure why some people are left-handed and others are right-handed, but scientists are working hard to find out.
When they do, they will have to explain why some of us look like we can use both hands.
