Most of us have noticed that when we get tired we can often yawn; however, there is no proof to link yawning with tiredness. In fact, there is no proof to suggest why we yawn at all, there are many theories but as yet none of them have been proved. The theories are quite diverse ranging from a need to supply our bodies with extra oxygen to a throwback from the early days of mankind whereby bearing their teeth was a way of warning each other, quite as to why this would cause yawning is unclear and why yawning hasn’t stopped after all this time when it serves no obvious purpose is unclear too. One of the theories involves the intake of oxygen acting like an airflow to cool the brain, rather much like the way in which a fan inside a computer cools the internal parts. This theory can relate to why we might yawn when we are tired, as it would indicate that our bodies are in a warm place, hence the warm brain – and tiredness is often linked to when we are warm, hence why it is advisable to keep the window open on the car door if you’re driving late at night and there is a risk of falling asleep (although in this situation it is more advisable just go to sleep).
The other main theory is that yawning involves a deep intake of breath which is needed to replace the lack of oxygen that is in our lungs – replacing the old oxygen that is sitting at the bottom of the lungs with fresh air. Quite as to why this may relate to tiredness and sleeping is unsure just as with many other theories, such as the theory that it is some sort of throwback to our caveman days where a yawn was seen as a warning due to the bearing of our teeth. Other reasons also seem unclear as to what link it might have with tiredness, as well as being equally as unproven as any other theory as to why we may yawn.
The fact that we sometimes we yawn when we are not tired and also that yawns have a contagious quality about them, or so it seems, suggests that maybe tiredness is not actually a factor in yawning rather it is some kind of coincidence or otherwise. Whilst at the same time, yawns may be associated with boredom; however, why do we yawn when we are not bored? The reasons behind this are very confusing and no one quite knows what it is that causes us to yawn as yet, despite all the debate. It may be a simple thing such as when we are tired we use less energy, therefore, we take this deep intake of breath, as in the case of the yawn every now and then, because our breathing rate has slowed, we may never know and it may be one of those things that is never proved.