Mitten Tree Day Day 340 of 2007 25 days left in this year

HAWAIIAN PROVERB OF THE DAY —
“When the mouth yawns, it is a night on which no fish are caught.”

THE MYSTERY OF YAWNING
Although humans have probably been yawning since before the Stone Age, we still don’t know why we do it.  Yawning is an involuntary action that causes us to open our mouths wide and breathe in deeply which causes us to draw in more air and our hearts to beat faster than  normal.

The claim that yawning is caused by lack of oxygen has not been scientifically substantiated. In fact, there are many theories about the nature of yawning.  A recent one raised in 2007 by Andrew C. Gallup and Gordon Gallup of the University of Albany states that yawning may be a means to keep the brain cool.

A similar theory is that yawning is used for regulation of body temperature. Yet another hypothesis is that yawns are caused by the same chemicals (neurotransmitters) in the brain that affect emotions, mood, appetite and other phenomena. These chemicals include serotonin, dopamine, glutamic acid and nitric oxide. As more (or less) of these compounds are activated in the brain, the frequency of yawning increases. 

Still another theory is that yawning is akin to stretching. Stretching, like yawning, increases blood pressure and heart rate while also flexing many muscles and joints. Another hypothesis suggests that yawning occurs to stabilize pressure on either side of the ear drums.

The well known contagious nature of yawning is  not understood any better. Researcher Catriona Morrison states, “We believe that contagious yawning indicates empathy. It indicates an appreciation of other people’s behavioural and physiological state.”

In non-humans, yawning might serve as a warning signal. Charles Darwin, in his book The Expression of the Emotions in Man and Animals, wrote that baboons use the yawn to threaten their enemies. For Adelie Penguins yawning is part of their courtship ritual.

Yawning Facts