Yawning is strange. It happens when we’re tired, when we see someone else doing it, and sometimes if we even just really think about it. But why do we do it?
Interestingly, nobody knows exactly why we yawn. It has physical and social triggers, but the jury is still out on the exact benefits.
We know that yawning begins long before birth, as early as in our 11th week in the womb. Once we start yawning, we don’t stop, though it’s not quite as simple as just yawning when we’re tired.
The most common belief is that yawning wakes us back up again. When we’re tired, the act of yawning can increase alertness and provide a short burst of energy.
This happens because yawning causes us to breathe in deeply. The action opens up the muscles in your skull and jaw, increasing blood flow to the brain, allowing cooler air in. It has therefore led researchers to believe that one of the reasons we yawn is when our brain is warming up.
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While there might be a slight correlation between warm temperatures and feeling dozy, there is no concrete evidence as to why cooling our brains down means we so regularly yawn when we’re tired.
Another recent theory is that yawning is a learned behavior, developed over thousands of years of human interaction. It is an obvious tell of fatigue, and it signals to those around us that we are tired, bored, under pressure or want to go to bed.
This would explain why it is so contagious. As a physical communication of how we feel, mirroring it from someone else can be linked to human empathy and togetherness. But that still doesn’t explain why we start yawning before birth.
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