How to become left-handed?

You don’t become left-handed, you’re born left-handed!

For researchers around the world, left-handedness is at least a subject as fascinating as the invention of the wheel! We make up around 10% of the world’s population, and yet we adapt. But how do we become left-handed? Is it a question of genetics? Development? Something else? Contrary to certain beliefs, the family environment – yes, it’s always the mother’s fault – has almost nothing to do with it.

The genetic basis of left-handedness

How do you become left-handed? Genetically, researchers are searching like Shaddocks, and they may end up succeeding in proving definitively that yes, there is indeed a left-handed gene or genes.

If you look hard enough, you always end up finding your lost glasses. What is known is that genetics play an important role in determining laterality.

Several studies have shown that left-handedness can be inherited and that it does not generate taxes. A study conducted by the University of Oxford revealed that if both parents are left-handed, there is a 46% chance that the child will also be left-handed, 17% if one of the parents is left-handed and 2% if neither parent is left-handed. Certain genes, such as LRRTM1, have been associated with a predisposition to left-handedness. Genetics alone cannot explain everything, because in this case we would observe much higher rates of left-handedness in certain families.

Prenatal development

As usual, certain things happen in the mother’s womb. Studies suggest that the position of the foetus in the womb may influence laterality. However, we notice manual asymmetry very early on in the foetal stage, which is thought to be genetic in origin and to result in an asymmetrical posture of the head. From this point onwards, the foetus is more likely to repeat movements with its right or left arm.

Very recent studies have shown that increased exposure to testosterone before birth could increase the probability of becoming left-handed. Perhaps we should carry out surveys in sports halls to see whether exercise makes people more left-handed! Prenatal environmental factors, such as maternal stress or a specific diet, could also play a role, but these studies are somewhat contradicted by twin pregnancies…

According to a study published in the Journal of Neuroscience, left-handed men account for around 12% of the male population, compared with 8% of women, suggesting a potential link with prenatal exposure to testosterone (and not postnatal, we’ve got that right!).

How do you become left-handed? Environmental and cultural influences

My beloved was convinced that I had influenced the laterality of our children, both of whom were left-handed like me. He was both right and wrong. Genetics and other factors no doubt have a lot to do with it, but perhaps the role model we are for our children also plays a part. After birth, environment and culture can also influence manual preference. On closer examination, some researchers have even gone so far as to study adoptive families in which parental mimicry is even more important: a few cases studied showed that children who were ‘born right-handed’ became left-handed when their adoptive parents were left-handed.

In some cultures, being left-handed was (and still is) frowned upon, leading some left-handed children to adapt and use their right hand. Tools and objects designed for right-handers can also force left-handers to develop a degree of ambidexterity.

According to a Stanford University survey, 11% of Western children are left-handed, while in some East Asian cultures this figure falls to around 3%, no doubt due to cultural pressures.

Left-handed, an advantage or not?

Left-handed people have a different cerebral organisation from a neurological point of view, which could give us some advantages in terms of creativity or in certain sports requiring unpredictable movements or very fast reflexes, such as fencing, racket sports or boxing.

Why are left-handed people so rare?

Because everything that’s rare is expensive! What’s surprising is that the prevalence of left-handedness has been stable for as long as humans have used their hands.

• Evolutionary theory: some researchers believe that the preference for the right hand could be linked to evolutionary advantages, such as efficiency in everyday tasks, but in that case, we would be increasingly rare.
• Social and cultural pressures: in many cultures, a preference for the right hand has historically been encouraged, thereby reducing the prevalence of left-handedness, and yet we resist! Left-handedness is less and less the norm, and the percentage of left-handers has returned to its original level.

Let’s keep exploring!

So, in the end, how do you become left-handed? There are a whole host of factors that science is still exploring. The little human raises his little left-handed fist, claiming a difference that will undoubtedly make him unique!