It may seem simple and even humorous, but The phenomenon of yawning is one of the most deeply rooted in our biology Basically, everyone yawns, regardless of what culture they belong to.
Furthermore, it is not only present in babies and even in fetuses of three months of gestation, but it also manifests itself in practically any vertebrate animal, from parrots to sharks.
But… what makes yawning so omnipresent in much of the animal kingdom? Why do we yawn, and why are yawns contagious? Are they useful for anything? Below we will address these questions and some more. But first, let’s start with the basics.
A yawn is the involuntary action of holding the jaws open, breathing in deeply for a few seconds, and closing the jaws again while exhaling briefly.
The yawns They 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 response to stressful situations that, sometimes, can catch us off guard, whether because we are tired or because we are sleepy.
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.
If we start from the idea that yawning It is basically taking in a lot of air through deep breathing we will easily come to the conclusion that yawning serves to oxygenate us.
However, this hypothesis has been refuted since the 1980s, when University of Maryland researcher Robert Provine observed that the frequency of yawning was the same regardless of whether one was in a very well-ventilated room or one with a lot of CO2.
At the moment, it is not known for sure what yawning is for, but a series of theories are being considered.
1. Exercise 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 which, depending on our mood or the social contexts in which we find ourselves, can remain almost completely relaxed for too long.
Thus, when we are bored or sleepy and adopt a neutral and expressionless face, yawning can be a wave of activity that allows that part of the body to regain muscle tone. It would be like an automatic way of waking up.
2. Prepare for a state of alert 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 sensation could help us clear our heads, 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.
An alternative explanation for why we yawn would be that this action allows you to “reset” the position of the jaws, making them fit together better than they did before. Likewise, 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 has no use, at least in our species. It is perfectly feasible that in our ancestors they would have been of some use but that along the way of evolution this adaptive advantage would have been lost, or that since its appearance in the most basic forms of vertebrates it would have been totally useless.
After all, a biological characteristic does not need to provide advantages to exist Evolution does not cause only the most adaptive traits to appear and survive, but there are others that do so despite not benefiting the species that carries them in any way. The pseudo-penis of female spotted hyenas is an example of this.
Why is yawning contagious?
Another of the great unknowns is why we are so prone to being affected by other people’s yawns. In fact, it has been seen that it is not even necessary to see others yawn; Thinking about yawning or seeing a photograph in which that action appears significantly increases the chances of being infected.
It is currently believed that mirror neurons are at the origin of this curious phenomenon which are responsible for initiating “mental rehearsals” about what it would be like to experience on our own skin what we are observing in real or imaginary people or animals.
