Do you ever think about ‘handedness’? If you are right-handed, you probably don’t have to since you belong to the vast majority who use it as the dominant hand. If you are left-handed, though, things may be difficult for you. It may make you wonder why naturally left-handed people are a minority and what causes handedness.
Sinisitrality or left-handedness makes people do their daily work with their left hand. This causes them to face daily problems using scissors, desks, notebooks, etc. Life’s difficult for them as things are created to make the lives of the right-hand users easier. Approximately 10% of the population are left-handed, obviously making them the minority.
Being left-handed has never been easy, especially for left-handed children. In medieval times, left-handed people were accused of being possessed by the devil. It was believed that the devil himself was left-handed.
The word ‘sinistrality‘ has been derived from Latin word ‘sinistra‘, which originally meant ‘left’. Now, we understand that the term ‘sinister’ is the connotation for ‘evil‘. On the other hand, ‘right’ is associated with being correct and just.
So, what is responsible for left-handedness or handedness in general? The first theory claims that natural selection has mostly produced individuals with the left side of their brains controlling their speech, language, etc. This left hemisphere is responsible for the control of the right hand resulting in the majority being right-handed.
Another theory that pertains to left-handers and a left-handed child talks about genetic mutation. Two alleles- the C gene and D gene, are associated with handedness (i.e. right-handed parents). While the D gene is found more often in people, the C gene is also present. D gene promotes right-handedness in people, although people don’t have a hand preference. However, a very small part of the population is left-handed.
An individual with a C gene has a 50% chance of being either left-handed or right-handed. One might wonder why left-handedness has not been forced out of the genetic pool, as it is not the dominant trait. Scientists claim that things are more complex, and the study is ongoing.
Meanwhile, just 10% of left-handers of the world’s population demonstrated right hemisphere activity for this task when studied. The vast majority of them, like most right-handers, processed language in the left half of the brain.
Simple theories have never stood up to scientific examination; environmental factors and genetics is no exception. Over the course of decades, when the mysteries of the DNA double helix were unraveled, handedness researchers pondered if this new information.
Others believe it has to do with the way the brain is divided into two halves, with the left half regulating the right side of the body and the right half controlling the left.
If most people’s brains are using the left hemisphere to manage complex language with fine motor skills, the reasoning goes, the right hand will be more dominant as well.
While there are those who are strictly right-handed or left-handed, there are also those who use both their hands equally. They are ambidextrous. Animals like Chimpanzees and Polar bears show handedness. All Polar bears are left-handed.
In the brain is where the arm and hand movements start, in the motor cortex, that sends a signal to the spinal cord that’s translated into a motion.