Yawns

[calibrax]

Why are yawns so infectious?

[andy hughes]

It's a throwback to our days as tribal primeval apes. When one ape smelled or sensed danger, he would yawn, which served as a silent warning to the rest of the tribe, as well as showing off his fighting fangs to the interloper. This would trigger a duplicate response from any other apes who saw it, so that the message would spread quickly and silently round the tribe. As with a number of other inbuilt safety measures, this is one that has not yet evolved out of mankind's physiology, even though the need for it has long since ceased. That's why when we see someone yawn, we get the subconcious urge to do the same. It is deemed sufficiently important as a defence mechanism that foetuses in the womb have the facilty inbuilt in the very earliest weeks of development.

[smudge]

How interesting Andy!

[andy hughes]

Actually, I forgot to mention - my response is the current perceived wisdom on the question, the truth is, no-one is really sure why we yawn, or why others join in, but this is reckoned to be a serious explanation. It used to be that people thought that we were taking in additional oxygen, but that theory was disprived when it was observed that developing foetuses - who don't breathe air - yawn in the womb.

[WaldoMcFroog]

But Andy, couldn't it also be argued that the 'silent warning' is equally invalid on the basis that there are no predetors in the womb..? ;-)

Indeed, if it's a subconscious urge that we've kept from prehistoric days, surely the lack of oxygen in the womb is irrelevant?

More importantly, if yawning were something related to a silent defence mechanism, which would surely also go hand in hand with an increased level of adrenalin, how come I yawn a lot when tired (generally in the entirely benign situation of when I'm with my wife, sitting at home, in front of the idiot box) but not when I'm walking down a street full of yobs and yobbettes..?

[Pickle]

Here's a scientific sounding but completely bogus theory that was going around at one time: We yawn to balance the air pressure on our eardrums. But balancing the air pressure on our own eardrums tends to unbalance the air pressure on the eardrums of other people nearby, so they have to yawn too, until the air pressure on everyone's eardrums is OK.

[andy hughes]

Waldo, yes your argument is absoultely valid. As I pointed out in my second response, no-one is really sure why we yawn, so one theory is pretty much as good as another.