Why Do We Yawn?
Everyone yawns, but no one knows why. We start when we are in the womb, and we do it through old age, but the purpose and survival value of yawning remain a mystery.
There is no shortage of theories but a dearth of experimental proof that any of them is correct. “The lack of experimental evidence is sometimes accompanied by passionate discussion,” said Dr. Adrian G. Guggisberg, the lead author. Hippocrates proposed in the fourth century B.C. that yawning got rid of “bad air,” and increased “good air” in the brain. The widely held modern view of this theory is that yawning helps increase blood oxygen levels and decrease carbon dioxide. If this were true, Dr. Guggisberg writes, then people would yawn more when they exercise. And people with lung or heart disease, who often suffer from a lack of oxygen, yawn no more than anyone else.
