It seems - nobody is sure of anything nowadays that yawning was once seen as a chance of evil spirits to enter the body while the soul slipped out. So, we began covering the mouth to frustrate the to-and-fro, but that hasn’t put a lid on certain vital questions such as: Who yawns?

Science replies: fish yawn on switching from one activity to another, chickens stand on tiptoe, flap their wings - and yawn. With its head out of the sand, the South African ostrich has been caught yawning. Dogs yawn like mad when they become aggressive, unless - and this goes for cats and apes, too - they are signaling peaceful coexistence.

Dr. Jacques Barbizet, of Saint Antoine Hospital, in Paris, studied yawning with radiography made every half second. He detected dilation of pharynx, larynx, nostrils and bronchial tubes; lifting of the eyebrows; lowering of the diaphragm; retreat of the tongue; a slight racing of the heart; increased flow of the blood to the brain; rhythmic lateral motions of the mandible; closure of the eyes; occasional tears and saliva, as well as, now and then, dislocation of the jaw.