A Beeb story (http://www.bbc.co.uk/news/health-16052112) suggests contagious yawning has its origins in animal or at least caveman behaviour – most likely to occur amongst family or friends, as some kind of ‘heads up’ signal.
All I know is that it was outlawed by my parents outside our own four walls (rude, they said) and by school teachers, who perhaps interpreted it as a sign of tiredness (go to bed earlier) or boredom (I’ll bore you, lad; just wait and see). Funny how what was probably a way for the tired body to wake up the brain with a fix of blood became a social phenomenon worthy of comment among our mentors!
Boadicea's Chariot 
Fascinating…
(yawn)
http://www.mydaily.co.uk/2011/11/02/lady-gaga-fur-coat-fishnets-london/
Cry, and you cry alone. Yawn, and…
Er …..and….?
One of our Jack Russells is a very yawny little dog.
He is generally affixed to spousal unit’s lap.
He wakes up and yawns and spousal unit returns the favour.
So, interspecies too and quite amusing to watch.