Picture: Jennifer Lawrence is left-handed
Picture: Jennifer Lawrence is left-handed
MARK RALSTON/GETTY

Left-handed people have been vilified and revered in history, often in the same breath.

Either they’re artistic geniuses, like Michelangelo and M C Escher, or they’re touched by Satan.

Approximately 10 per cent of the population is left-handed, and the reason why has been a source of scientific and sociological debate for many years.

General consensus deemed that handedness was a biological and genetic predisposition.

The theory argued that evolutionary natural selection caused speech and language control to develop in the left hemisphere of the brain. This is the side that controls the right hand and over time, predisposed the majority of the population to genetic right-handed development.

New research provides a different origin story.

The cause of handedness is not found in the brain, but the spinal cord.

That’s the conclusion of a new study by lecturer Dr Sebastian Ocklenburg and his team. Together with colleagues from the Netherlands and South Africa, the bio-psychologists confirmed that gene activity in the spinal cord is “asymmetrical already in the womb”.

In the journal eLife the authors write:

These results fundamentally change our understanding of the cause of hemispheric asymmetries.

Previous research confirms that unborn children show a preference to suck either their left or right hand in the 13th week of pregnancy. While the motor cortex in the brain is in charge of hand and arm movements, it is not connected to the spinal cord from the beginning.

The team also found that environmental factors cause symmetry, which affects the baby in the womb. These epigenetic factors may change the enzyme interaction around the baby, and in turn affect how the genes develop, and whether the unborn child will prefer their right or left hand.

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