WHY do we yawn? For no reason, apparently. It's an essential part of normal lung development in unborn babies, but serves no purpose in adults, say two researchers in the US.
Other theories on the significance of yawning have ranged from social cues to a craving for oxygen ("The big yawn",
Roberts and his colleague Will Blackburn of the Greenwood Genetic Center in South Carolina think these actions reduce pressure in the lungs and clear out webs of tissue that might block the airways. Fetal lungs secrete liquid that makes up the amniotic fluid, along with urine. If it can't escape the ...
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