BY- JAYA CHOUDHARY
About 10% of the world’s population, or 700 million people, are left-handed, and August 13 is designated as International Left Hander’s Day. Despite accounting for up to 10% of the population, left-handed people are often labeled as odd. In fact, the Italian word for left ‘sinistra’, is derived from the Latin word for sinister. But the real question is why certain people are born left-handed?
According to studies dating back to the 1980s, our preference for the right or left hand is most likely decided before we are even born. Ultrasound screening revealed that a preference for moving the left or right hand emerges in the womb as early as the eighth week while sucking the right or left thumb begins in the thirteenth week. However, a group of scientists from the Netherlands, the United Kingdom, and China conducted a genetic study to determine what factors led to the nervous system’s left-right variations.
The researchers discovered that gene activity in the spinal cord was asymmetrical in the womb, which may explain whether people became left or right-handed. Arm and leg movement start in the brain, in an area, called the motor cortex. This cortex sends signals to the spinal cord, which allows the movement of our arms and legs. The study concluded that variations in gene expression, rather than the genes themselves, have an effect on species.
These changes are often caused by environmental factors and can have an impact on a baby’s development. Enzymes can bind methyl groups to DNA as a result of these environmental factors, affecting and minimizing gene reading. When it comes to the rarity of left-handed individuals, researchers conclude that a high level of engagement, rather than something strange or sinister, plays a key role. ‘The more social the animal where cooperation is highly valued, the more the general population will lean towards one side,’ says researcher Daniel Abrams.
Using a mathematical model, researchers discovered that the low percentage of lefties is the result of the balance between cooperation and competition in human evolution. All would be even-handed if communities were fully cooperative. However, if competition were a great factor, the population would be split 50/50. In reality, we humans seem to prefer right-handedness more than left-handedness.
So, considering their genetic predisposition, someone who deviates from this may have been conditioned to use the left hand primarily. As a result, left-handedness is an uncommon occurrence. It’s partly genetic and partly environmental that people tend to use one side over the other.