Why do we yawn and what is the function of yawning?

It may sound simple and even humorous, but the phenomenon of yawning is one of the most deeply ingrained in our biology. Basically everyone yawns, regardless of what culture they belong to.

In addition, it is not only present in babies and even three-month-old fetuses, but also manifests itself in practically any vertebrate animal, from parrots to sharks.

But... what is it that makes yawning so ubiquitous in much of the animal kingdom? Why do you yawn, and why do yawns spread? Are they good for anything? We will address these issues and a few more below. But first, let's start with the basics.

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What is a yawn?

A yawn is the involuntary action of holding the jaws open, taking a deep breath in for a few seconds, and closing the jaws again while exhaling briefly.

Yawning are closely linked to the sleep-wake cycle that regulates the hormone called melatonin, and that is why for many years it has been believed that it is a physiological phenomenon related to the level of brain activity and the responding to stressful situations that can sometimes catch us off guard, either because we are tired or because we have dream.

In short, yawning is something closely linked to our evolutionary origins and that has penetrated the most basic functioning of our nervous system. Now, knowing this does not tell us anything concrete about its usefulness. If we want to know what needs this curious biological mechanism could respond to, it is necessary to carry out specific research to find out.

What is it for?

If we start from the idea that yawning is basically taking in a lot of air by taking a deep breath, we will easily come to the conclusion that yawning serves to oxygenate us.

However, this hypothesis has been disproved since the 1980s, when University of Maryland researcher Robert Provine observed that the frequency of yawning was the same regardless of whether it was in a very well ventilated room or with a lot of CO2.

At the moment, it is not known for sure what the yawns are for, but a number of theories are being considered.

1. Exercise the facial muscles

One of the hypotheses that could explain the function of yawning is the possibility of keeping fit and tone the small muscle groups of the face that, depending on our state of mind or the social contexts in which we find ourselves, they can remain almost totally relaxed for too long.

Thus, when we get bored or sleepy and adopt a neutral and expressionless face, yawning can be a surge of activity that allows that part of the body to regain muscle tone. It would be like an automatic way to stretch ourselves.

2. Prepare for alertness and concentration

Keeping the muscles of the face activated does not have to serve only to keep them ready for action. It can also have a psychological effect: noticing that feeling could help us to clear ourselves, which would make the brain more active and able to pay more attention to the important things. It is, let's say, a looping effect: the nervous system moves certain muscles so that muscular activity keeps us more awake.

3. Correct the position of the bones

An alternative explanation for why we yawn would be that this action allows to “reset” the position of the jaws, making them fit together better than they were before. Similarly, the same movement can help clear the ears by correcting air pressure differences between the inner and outer ear.

4. It has no function

Another possibility is that yawning is useless, at least in our species. It is perfectly feasible that in our ancestors they would have served something but that along the path of evolution that adaptive advantage would have been lost, or else since its appearance in the most basic forms of vertebrates it was something totally Useless.

After all, a biological characteristic does not need to suppose advantages to exist. Evolution does not make only the most adaptive traits appear and survive, but there are others that do so despite not benefiting the species that carries them at all. The pseudo-penis of female spotted hyena is an example of this.

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Why is yawning contagious?

Another of the great unknowns is why we are so prone to the yawns of others sticking to us. In fact, it has been found that it is not even necessary to see others yawn; Thinking of a yawn or seeing a photograph in which that action appears significantly increases the chances of it being infected.

It is currently believed that mirror neurons are at the origin of this curious phenomenon, who are in charge of initiating “mental tests” on what it would be like to experience on our own skin what we are observing in real or imaginary people or animals.

Mirror neurons may be the neurobiological basis for empathy, but one of its side effects could be yawning.

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