No matter how many times we have experienced it, it is still pretty impressive that one of our hands is capable of writing Shakespeare, while the other hand can barely work out how to pick up a pen.
As a marker of difference throughout our lives, we’ve all wondered why we end up being right or left-handed, without seemingly having any choice in the matter.
The reason for our right and left-handedness was long presumed by scientists to be a result of activity in the right and left hemispheres of our brain during foetal development.
But now a new study has shown that it is actually the spinal cord that is to blame, not the brain.
The team, from Ruhr-Universitat Bochum, Germany, used foetal ultrasounds to try and trace the earliest signs of gene activity in marking asymmetry and preference.
They saw that as early as eight weeks, a preference for the right or left hand can be seen. And from the thirteenth week of pregnancy, the foetus will suck either their right or left thumb.
It is well known that arm and hand movements are initiated by the motor cortex in the brain, which sends a signal to the spinal cord.
However, at eight weeks development, the motor cortex hasn’t yet made this connection, meaning that precursors of handedness are apparent before the brain is telling the spinal cord what to choose.
From this, authors Dr Sebastian Ocklenburg, Judith Schmitz and Dr Onur Güntürkün, concluded that the spinal cord is responsible for the distinction, not the brain.
Explaining: “These results fundamentally change our understanding of the cause of hemispheric asymmetries.”