Why do we yawn and what is the function of yawning?
It may seem simple and even humorous, but the yawning phenomenon is one of the most deeply rooted in our biology . Basically, everyone yawns, regardless of the culture to which they belong.
In addition, it is not only present in babies and even in fetuses of three months of gestation, but also manifests itself in practically any vertebrate animal, from parrots to sharks.
But ... what is it that makes yawning an omnipresent fact in much of the animal kingdom? Why yawn, and why yawn? Are they useful for something? We will now address these issues and some more. But first, let's start with the basics.
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What is a yawn?
A yawn is the involuntary action of keeping the jaws open, inspiring deeply for a few seconds and closing the jaws again while briefly expiring.
The yawns are closely linked to the sleep-wake cycle that regulates the hormone called melatonin, and that's why for many years it has been thought to be a physiological phenomenon related to the level of brain activity and the response to stressful situations that can sometimes catch us off guard, either because we are tired or because we are sleepy.
In short, yawning is something very linked to our evolutionary origins and that has entered into 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 to what needs this curious biological mechanism could respond, it is necessary to carry out concrete investigations to find out.
What is it for?
If we start from the idea of yawning it's basically getting a lot of air through a deep breath , we will easily reach the conclusion that the yawn serves to oxygenate us.
However, this hypothesis has been refuted since the 1980s, when the University of Maryland researcher Robert Provine observed that the frequency of yawning was the same regardless of whether he was in a well ventilated room or with a lot of CO2.
At the moment, it is not known with certainty what the yawns are for, but a series of theories is being considered.
1. Exercise the facial muscles
One of the hypotheses that could explain the function of yawning is the ability to keep in shape and tone up the small muscle groups of the face which, depending on our state of mind or the social contexts in which we find ourselves, can remain almost totally relaxed for too long.
Thus, when we get bored or sleepy and adopt a neutral and inexpressive face, the yawning can be a wave of activity that allows that part of the body to recover muscle tone. It would be like an automatic way to stretch ourselves.
2. Prepare for alertness and concentration
The fact of 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, which would make the brain more active and able to pay more attention to important things. It is, let's say, a loop effect: the nervous system moves certain muscles so that this muscular activity keeps us more awake.
3. Correct the position of the bones
An alternative explanation for what yawn would be that this action allows to "reset" the position of the jaws , making them fit again better than they were before. Similarly, the same movement can help clear the ears by correcting differences in air pressure between the inner and outer ear.
4. It has no function
Another possibility is that the yawns have no use, 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 that since its appearance in the most basic forms of vertebrates was something totally useless.
After all, a biological characteristic does not need to assume advantages to exist . Evolution does not mean that only the most adaptive traits appear and survive, but that there are others that do so despite not benefiting the species that carries them. The pseudo-penis of mottled hyena females is an example of this.
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Why is yawning contagious?
Another of the big questions is why we are so prone to being glued to the yawns of others. In fact, it has been seen that it is not necessary to even see others yawn; thinking of a yawn or seeing a picture in which that action appears significantly increases the chances of being contagious.
Currently, it is believed that at the origin of this curious phenomenon are mirror neurons , which are responsible for initiating "mental trials" on what it would be like to experience in our own skin what we are observing in real or imaginary people or animals.
Mirror neurons can be the neurobiological basis of empathy, but one of its side effects could be yawning.
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