If you’re a leftie – and by that we mean left-handed, not in Trump’s way – you’ll know all too well about the pain of desks made for right-handed people, scissors that aren’t meant for you, and ending up with a silver, leaded hand every time you go to draw something with a pencil. But what exactly do you have to blame for hearing the phrase “Are you left-handed?” (usually accompanied by a gawping stare) every time you write something?
Over the years, a fair few theories have been put forward to explain why some people are right-handed while other people lead with their left – in Medieval times, it was even considered a sure sign you were possessed by the Devil – but now, it appears scientists might actually have cracked it, with some surprising results.
For a while, doctors have believed that gene activity in the brain defines whether someone is left or right-handed – there is either more activity in the left hemisphere, which controls the right side of the body, or vice versa. But according to a study published in the biomedical science journal eLife, it’s actually got a lot less to do with our brains and a lot more to do with our spines. Yes, you read that right, it’s your spine that controls the way your hands work.
By keeping an eye on the gene expression taking place within the developing spinal cords of growing babies inside the womb between the eighth and twelfth weeks of pregnancy, researchers led by biophysicists at Ruhr University Bochum were able to figure out that this asymmetry exists in the spine long before it’s ever even connected up to the part of the brain that controls movement.
But, while it would be easy to think that gene asymmetry would be dictated by inherited traits or genetic mutations, it actually seems that it is environmental factors which impact the baby in the womb and make the biggest difference.
Even more compellingly, the gene activity appears to be linked to the very parts of the spine responsible for sending electrical messages to the hands, arms, legs and feet. Incredibly, babies have been shown to have a preference as to whether they suck their left or their right thumb from as early as the 13th week of pregnancy.
There’s definitely still work to be done, however, because the researchers aren’t quite sure what exactly these environmental factors actually are yet; either way, they alter the way the enzymes that develop around the baby, which in turn affects the way the genes develop.
But whatever the cause is, all in all it’s fair to say that left-handed people are pretty damn special – it’s estimated that just 10 per cent of people have the trait, and some scientists even think that they are more likely to fare better in combat, have better spatial awareness and can process information quicker than righties.