While no one has been able to definitively explain this, there are many hypotheses that have been building for over a century, and the evidence points to some kind of genetic influence. Why? Because the percentage of left-handers is about the same, wherever you look in the world.
For those of you who regularly kick a ball, you will know that there are natural asymmetries throughout the body; they are likely to opt for one foot over the other when it comes to kicking.
These asymmetries can be found in everything from our feet to our ears to our eyes to the design of our brains, explains Hannah Fry in BBC Future.
If you hold your thumb at arm’s length, and look at it with one eye and then the other, the eye that seems to show the thumb closest to you is the strongest. Similarly, you probably tend to answer the phone or listen behind closed doors with one ear rather than the other; that’s your strongest ear.
But why aren’t left-handed and right-handed people born in roughly a 50:50 ratio?
Some experts suggest that social cooperation, developed over thousands of years, has given right-handers dominance. In other words, when communities act together, in terms of sharing tools and living spaces, it pays to use the same hand as everyone else.
Others suggest what does it have to do with the way the brain is organized into two hemispheres; with the left half controlling the right side of the body and the right half controlling the left side of the body.
If most people’s brains use the left hemisphere to control intensive language and fine motor skills, that bias is thought to make the right hand more dominant as well.
In fact, one of the more unusual hypotheses to explain the rarity of left-handedness is that a genetic mutation in our distant past caused the language centers of the human brain to shift to the left hemisphere, effectively causing right-handedness to dominate. , Alasdair. Wilkins explains for io9 .
And while genetics likely plays a role in determining the hand, it’s not the whole answer. Left-handed parents are more likely to have left-handed children than right-handed parentsa preference that can even be seen in utero, but they still tend to have more right-handed children overall.
So far, DNA studies have been unable to identify which gene might be responsible for increasing the chances of being left-handed, and recent research generally accept that probably there are dozens of genes that play a role in determining whether we end up writing with our left or right hand.
In addition to that, other studies have linked factors such as estrogen levels and the birth position with different levels of lefties and righties.
In short, there seem to be a lot of considerations at play, and researchers are having a hard time linking them all. That means we still can’t tell you exactly why he was born left-handed or right-handed, but scientists are clearly hard at work finding an answer.
And when they do, they’ll have to explain why some of us seem to be ambidextrous too.