Left Handed? It's All Because Of What Happened Before You Were Born

In a world designed for right-handed people, being a leftie can be a real struggle.

The preference for using one hand over the other puzzled scientists for a long time, with many coming up with the idea that it must have something to do with genetic differences between the right and left hemispheres. Yeah, science.

However, strange as it may seem, the real reason you're left-handed may have more to do with your spine than your brain.

Research carried out by Sebastian Ocklenburg, Judith Schmitz, and Onur Gunturkun from Ruhr University Bochum, along with other colleagues from the Netherlands and South Africa, found that gene activity in the spinal cord was asymmetrical in the womb and could be what decides whether someone will be a leftie or a righty.

Limb movements begin in the motor cortex before being sent as a signal to the spinal cord which then translates them into motions.

What the researchers found was that babies can already make movements and have a favourite hand before the brain and the spinal cord have had a chance to connect.

In order to further examine this, the researchers analysed gene expression in the spinal cord during the eighth to the 12th week of pregnancy.

What they found were significant differences in the left and right segments of the spinal cord, where arm and leg movement is controlled.

They determined that it could all be down to something called epigenetics - or how organisms are affected by changes in their gene expression rather than in the genes themselves.

This could affect the right and left parts of the spinal cord differently, determining whether a child will be right or left-handed. However, none of that explains why lefties are so rare.

In order to try and solve this mystery, researchers at Northwestern University put a mathematical model together to show that the low percentage of left-handed people was likely to be down to evolution.

"The more social the animal - where cooperation is highly valued - the more the general population will trend toward one side," Daniel Abrams, an assistant professor at the McCormick School of Engineering and Applied Science who helped develop the model, told LiveScience.

"The most important factor for an efficient society is a high degree of cooperation," he added. "In humans, this has resulted in a right-handed majority."

This means that while genetics do have a part to play in handedness, there are social and environmental factors at work, too.

Schmitz, one of the authors of the new study, explained to Business Insider how bird research can show how genetics and environment can be the cause.

"In chicken and pigeons, a genetic factor determines the position in the egg before hatch - the embryo is curled such that the right eye is turned to the semi-translucent eggshell, while the left eye is covered by the embryo's own body," she said.

"Thus, the right eye is stimulated by light before hatch, whereas the left one is mostly light deprived. This combination of genetic and environmental factors (light) induces a visual asymmetry - pigeons and chicken are better in visual discrimination, categorization, and memorization of visual patterns with their right eye than with their left eye. If chicken or pigeon eggs are incubated in darkness, the development of this asymmetry is prevented."

So, there you have it lefties. Mystery solved...sort of.

Featured Image Credit: PA

Paddy Maddison

Paddy Maddison is a freelance journalist and frequent contributor to LADbible. He specialises in men's lifestyle, music and news, which has seen him work with publications including ShortList, FashionBeans, Menswear Style and many industry-leading brands. Contact him at [email protected]

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