Are You Born Right-handed? Is It A Coincidence To Be Left-handed?

Today, almost nine out of ten people are right-handed. That leaves a percentage of left-handers in the world only at 10%. What determines this distribution? Is it the fruit of luck? Is it chance or genetic to be right-handed? Do we acquire it with practice? Can I become left-handed? Does it depend on our tastes?

The explanation is not that simple. There have been many investigations that have been done in this regard and none turns out to be entirely conclusive. However, within this ambiguity there are two hypotheses that seem to enjoy greater scientific support.

For both explanations, the causes of being right-handed or left-handed are neurological, that is, a consequence of a process of evolution of our nervous system. Therefore, we know with certainty that we would not be born with this condition nor that it is not the result of chance, but that we become such during our early childhood. How is this process?

Responsible is the brain

The first of these theories has prevailed for years and provides a neurological explanation of brain origin, that is, for it, being right-handed or left-handed is determined by the brain and depends on the “laterality” of the person.  Laterality is the preference for using one of the symmetrical parts of the body: hand, eye, foot, ear …

At an anatomical level, this concept is symmetrical, but at a functional level, it is asymmetric. There is laterality when one of the sides of the body predominates over the other at the time the person performs activities (writing, opening doors, playing tennis …). Left-handers have it left and right-handers right.

Laterality is forged between the ages of three and six and is fully formed at seven. If by the age of five the child has not developed it, it is necessary to see a specialist.

Lateralization

Necessarily, to understand this first theory, it is necessary to explain the concept of lateralization, a process that depends on the hemispheric dominance of the subject. Broadly speaking, it can be said that the right cerebral hemisphere “directs” the movements of the left side of the body and vice versa, the left hemisphere governs those of the right side. Therefore, it can be deduced that:

• Right- handed people : left hemispheric dominance and right laterality.
• Left-handed people : right hemispheric dominance and left laterality.

The determinant is the spinal cord

Recently, researchers from the Ruhr University of Bochum (Germany) assured that the cause of the choice of one laterality or another is not the brain, but the spinal cord. They found that at eight weeks’ gestation there are already marked genetic differences between left-handed and right-handed people.

That is, since the fetus is in the womb, the genes in the spinal cord responsible for controlling the movement of the limbs are already different in one group and another. For example, the little ones already choose to suck the thumb of one hand or the other. How can it be possible?

The process is as follows: the cerebral cortex sends motor commands to the spinal cord and the spinal cord, in turn, controls the movements of the child’s legs and arms. The researchers’ finding focuses on the fact that at eight months the baby still does not have communicated the cerebral cortex and the spinal cord, so the only person responsible for its movements can be the spinal cord.

For them, the explanation of laterality (the preference of use) would be found in epigenetics. That is, in the influences that the environment has on the genes and that affect the left or the right of the spinal cord in different ways.

And people like Rafa Nadal? Are they right-handed, left-handed, ambidextrous?

If you have not yet identified yourself as right-handed or left-handed, it is likely that your laterality has not developed in a completely correct way. When it occurs, children may be ambidextrous, have cross or cross laterality.

• To be ambidextrous is to have undefined laterality, that is, there is no hemispheric dominance, and, therefore, there is an indifferent use of both symmetrical parts of the body. They are children who can do activities indistinctly with the right and the left.
• Crossed or mixed laterality exists when there is an exchange of its lateralities. For example, the case of Rafael Nadal, whose dominant eye is the right (he is right-handed), but his dominant hand is the left.

• Disgruntled laterality occurs in children who have been externally influenced to change laterality (the most common case is that of a left-handed child who is forced to write with the right). Thus, in activities not mediated by culture, he uses his “natural” hand, such as brushing his teeth, greeting or pushing something.

This upset laterality is related to the poor treatment that language has traditionally had with lefties. To do things “right” is to do them well and “to be right-handed” is to be skillful, but the evolution from Latin sinister to Spanish “sinister” has not been so kind. In fact, in many countries, such as China, someone who uses the left hand is still seen badly and children are corrected.

There are still many unknowns to solve in relation to how we become right-handed or left-handed. However, neurological investigations that attribute the cause to the brain and spinal cord are closer to providing us with an irrefutable scientific explanation.