Disclaimer: guaranteed, at some point, while reading this you will feel an irresistible urge to yawn. And you will yawn.

Yawning, aka oscitation, is a biological process during which we simultaneously inhale air, stretch our eardrums and follow all this with an exhale. It seems simple and straightforward and we all yawn – from grown humans and fetuses to cats, dogs and even snakes. The average person will yawn over 240,000 times over their lifespan but the real physiological reason for yawning is yet to be discovered. A yawn can be caused by anything from boredom to sleepiness, hunger or stress.

Yawning has been perplexing scientists all over the world for thousands of years now. So much so that back in 2010, a first ever International Conference on Yawning was held in Paris. Over a dozen yawning specialist from all over the world were invited to discuss topics like “Yawning over a Lifespan”, “Yawning in Non-Human Primates” or “The Theory of the Hidden Sexuality of the Yawn.” And still, no one really knows what yawning is all about. However, there’s been plenty of theories throughout the centuries…

Early hypotheses for yawning

The first ever theory on yawning came from Hippocrates in 400 BC, who believed the process released ‘bad air’ from the lungs before a fever: “Yawning precedes a fever, because the large quantity of air that has accumulated ascends all at once, lifting with the action of a lever and opening the mouth; in this manner the air can exit with ease.” Nowadays we know, that this theory was not correct but wasn’t until over a thousand years later when this view was even challenged. In 1671, Jan Baptiste van Helmont wrote ‘Principles of medicine and physics for healing diseases’, in which, for the first time in years, challenges Hippocrates idea, saying that yawning comes from the ‘orifice of the stomach’, as it is easily moved by the imagination. Few years later on in 1692, Pierre Brisseau also proposed a different reason for yawning – it was meant to be a sign of an impending epilepsy attack.

A breath of relatively fresh air in explanations for yawning, came in the 18th century, with the main man Johannes de Gorter, being at the forefront of history of knowledge of the yawn. He hypothesised that yawning improves brain oxygenation and this idea along with others claiming increase in heart rate or sweating, persisted over two centuries until contested. Modern tests have shown that the heart rate, sweating or brain’s electrical activity do not increase after yawning, therefore the reason for yawning still remained a mystery.

Modern ‘yawn science’

One of the more ridiculous modern claims, as to why we yawn was produced by Wolter Seuntjens, a Dutch scientist, who claims that yawning has an erotic side, he discusses links he’s found in literature: “In discussing pathology I discovered that yawning and spontaneous ejaculation were mentioned concomitantly in terminal rabies. (…) In discussing pharmacology I found a link between yawning and spontaneous orgasm in withdrawal from heroin addiction. Likewise, yawning and sexual response were associated as clinical side effects of several antidepressant drugs. In one publication an undeniable causal relation was reported: both spontaneous and intentional yawning provoked instantaneous ejaculation orgasm.” Seuntjens and fellow academics, admit they still do not understand the links between yawning and sex, and struggle to distinguish between a sleepy yawn and arousal yawn.

The other, maybe more believable theory, came in 2005 from Dr Robert Provine, who believes that yawning “stirs up our physiology, and it plays an important role in shifting from one state to another”. This claim has been repeated by few other studies, one of which even likened yawning to having a dose of caffeine – this claim was supported by the observation of yawning in athletes or musicians prior to their performance. However, some studies, and this is where things get more interesting, supported a different theory in which yawning has a social bonding function. We have all experienced how contagious yawning can be – even thinking of yawning can make you yawn (and we assume you’ve yawned at least once or twice while reading this) – turns out this effect is not limited to humans, and is present in other species, for example dogs who can yawn, if they see their owners yawn. This has been contributed to the emotional bonds they have with their owners. Some believe that people who are more empathetic than others, can find yawning a lot more contagious.

In 2007 another theory emerged, from Andrew Gallup and Gordon Gallup, claiming that yawning has a thermoregulatory function and can work as a brain cooling mechanism. So far this theory remains most believable explanation for yawning but the scientists all over the world still do not agree on a definite reason behind a good old yawn.

Why is yawning strange

Not only lack of reason for yawning makes it very strange. While it was always considered of minor medical importance, back in 1794 Erasmus Darwin (Charles’ grandfather), first observed involuntary movement in a paralyzed arm while yawning. Modern studies have shown that about 80% of patients with hemiplegia, can indeed move their paralyzed limbs during a yawn – the reasons for this, much like the overall reason for yawning, is still a mystery in the medical field yet to be discovered. Who knows, maybe yawning holds the answers to many of our modern day medical problems?