What makes you a lefty or a righty?

It is not the brain that determines whether a person is a lefty or a righty, but the spinal cord, a study has claimed.

Until now, it had been assumed that differences in gene activity of the right and left hemisphere might be responsible for a person's handedness - people's tendency to naturally favour the use of one hand over the other.

But the recent study demonstrated that gene activity in the spinal cord is asymmetrical already in the womb and could be linked to the handedness of a person.

"Our findings suggest that molecular mechanisms for epigenetic regulation within the spinal cord constitute the starting point for handedness, implying a fundamental shift in our understanding of the ontogenesis of hemispheric asymmetries in humans," said Sebastian Ocklenburg from Ruhr University Bochum in Germany. According to ultrasound scans carried out in the 1980s, a preference for moving the left or right hand develops in the womb from the eighth week of pregnancy. From the 13th week of pregnancy, unborn children prefer to suck either their right or their left thumb.