The New Yorker:
In 1923, Sir Francis Walshe, a British neurologist, noticed something interesting while testing the reflexes of patients who were paralyzed on one side of their bodies. When they yawned, they would spontaneously regain their motor functions. In case after case, the same thing happened; it was as if, for the six or so seconds the yawn lasted, the patients were no longer paralyzed. What’s more, Walshe reported that some of his patients had noticed “that when the fingers are extended and abducted during a yawn, they are able to flex and extend them rapidly, a thing they were unable to do at any other time. Indeed, one man added that he always waited for a yawn so that he might exercise his fingers in this way.”
Walshe concluded that yawning was activated by a primal center of the brain that fell outside conscious control. One’s ability to yawn could thus remain completely intact, even when “cortical control is more or less completely abolished over the musculature of one half of the body.” Yawning, then, was one of our most primitive, fundamental behaviors—a conclusion that echoed Charles Darwin’s observation, in 1838, that “seeing a dog & horse & man yawn, makes me feel how much all animals are built on one structure.”
Yawning is one of the first things we learn to do. “Learn” may not even be quite the right word. Johanna de Vries, a professor of obstetrics at Vrije University Amsterdam, has discovered that the human fetus yawns during its first trimester in the womb. And, unless we succumb to neurodegenerative disease, yawning is something we keep doing throughout our lives. “You don’t decide to yawn,” Robert Provine, a neuroscientist and the author of “Curious Behavior: Yawning, Laughing, Hiccupping, and Beyond,” told me. “You just do it. You’re playing out a biological program.” We yawn unconsciously and we yawn spontaneously. We can’t yawn on command—and we sometimes can’t stop ourselves from letting out a big yawn, even at the most inopportune times. (Case in point: Sasha Obama’s infamous yawn during her father’s 2013 Inaugural Address.) But what, precisely, are we accomplishing with all this yawning? If it’s so evolutionarily old, it must be doing something important to have survived.
Read the whole story: The New Yorker