As I think I've remarked before in this space, there are a number of things fundamental to being human that science still cannot fully explain. These "mundane marvels" interest me — I'm thinking of laughing, crying, sleeping . . . and yawning. We yawn 25,000 times in our life. Fetuses do it, apparently. We do it when we're bored, anxious, hungry, tired.
And that's the problem. Nobody has the answer. Or, there are too many answers. Have a look at this article, which gives you something of the essence of Wolter Seuntjens's dissertation, a work in which he presented "a systematic-encyclopedic overview of all available knowledge about yawning." Have no fear, the short article is considerably less than encyclopedic. But it does shoot down most of the theories as to why we open wide. And it walks us through some theories we might never have imagined (I speak for myself), such as a connection with sex.
The question of why we yawn is interesting enough to have engaged the attention of the Library of Congress, if you can believe it. And the best thing to come from it was a link over to a site by one Dr. Walusinski, a site that does approach encyclopedic status. I learn that there was an international conference on yawning held in Paris in 2010 (love the logo; see at the right, above) and that there's a neural basis to contagious yawning, though I couldn't tell you what it is. But by then I was weary and had to get up and stretch — and yawn — taking with me, though, from the good doctor's site the pleasing fact that the stretching and stiffening of the spine I did while yawning is known as "pandiculation."
*photo credit Sean Drelinger