Left handedness occurs in few people. So few in fact that around 85% of the population are actually right handed. But why do we have left and right-handed people?
Previously, it had been thought that the preference for using our left or right hand to write, eat or even hold a tennis racquet was determined by gene differences in the right or left hemisphere of the brain. However, research published by Ocklenburg et al., suggests otherwise. Their research printed in the journal eLife states how our preference for handedness comes from hemispheric asymmetries within the spinal cord and not as previously thought, the brain.
Our preference for using our right or left hand begins in the womb from around 8 weeks of pregnancy. As such, unborn children begin to suck their preferred thumb at approximately 13 weeks and so the inclination to be left or right handed is born.
The left and right hemispheres of the brain control the opposite sides of the body. In other words, if you’re right handed the left side of your brain is in control and vice versa. For the majority of people, the left hemisphere is the dominant one and controls speech as well as hand actions. As humans have evolved they have used either their left or right hand to hold tools, give hand gestures and hold a pen. Psychologists have speculated that our use of tools and hand gestures played a significant role in the development of our speech.
Being left or right handed is not something you inherit from you’re parents either. It is instead influenced by environmental factors. Although not entirely sure what these environmental factors are, scientists believe they change how enzymes work around the developing body. Thus, influencing the asymmetrical genetic activity within the spine.