Why do we yawn?

Involuntary and soothing, everybody does it from unborn babies to the wildest of animals.

Yawning, often triggered by fatigue or boredom , is the inhalation of air with our mouths wide open. But why do we yawn? There are many theories over the years to try and figure out the core reason.

Here is a video of ideas and theories on why we yawn:

(Compiled by Tashreeq Vardien, Health24, January 2013)

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Foetuses yawn in the womb