Roughly one tenth of the world’s population is left-handed. Despite what many people may think, being left-handed or right-handed is not a choice and it can even be determined while a baby is growing in the womb. Though it was previously thought that genetics was the only factor that played a role in determining hand preference, research that started 30 years ago suggests otherwise. In fact, research from the 1980s showed that hand preference could be determined as early as the eighth week of gestation, or pregnancy. However, a recent study done by researchers from Ruhr University Bochum in Germany has found that the potential determining factor of hand preference is actually the spinal cord. Through the study, it was discovered that gene activity in the spinal cord was asymmetrical in the womb. The arm and hand movements of a fetus begin in the part of the brain known as the motor cortex. The motor cortex then sends a signal to the spinal cord that translates into a motion; however, the motor cortex and spinal cord do not connect until the first trimester is over. This means that the fetus technically has the ability to move around and choose a favourite hand before its brain connects to its spinal cord and starts controlling the rest of its body. This discovery prompted the researchers to analyze the gene expression in the spinal cord in the eighth to twelfth week of pregnancy. They ultimately found remarkable differences in the right and left sections of the spinal cord that control arm and leg movement. It was concluded that epigenetics, changes in organisms caused by modification of gene expression, was at play and could ultimately determine hand preference. However, more research needs to be conducted to ultimately determine what causes hand preference. For now, we will continue to enjoy the mystery behind those who are left-handed.
