What does sticking your tongue out at someone mean?

Go to Desmond Morris for this one. He sees it as a literal “Fuck You!” gesture (The arm is a super-phallus that it being forced into some aperture until stopped by the edge, indicated by the other arm stopping it at the elbow).
Makes sense to me.
And, if true, a very different sort of comment than the stuck-out tongue. The tongue is a childish and not very serious little rejection. The arm-and-fist is a serious, adult, violent insult. Even if done in a kidding way between friends it undeniably packs more of a punch, which is understandable if the Morris explanation is true.

Followed by an unzip and an awkward scamper over to press your sack on someone’s thigh.

Thigh? Oh, yes, I guess that would be a little less offensive.

I remembered that it was a Tibetan custom to stick out one’s tongue as a greeting, and googled about as to why. My first rather wiseass simple thought was that it would be an extreme sign of respect to stick your tongue out in that sort of freezing cold environment. But, I was on the wrong track: From this site :

So, that custom would be tongue as passport, rather than an emotional reaction. Though, I remember reading previously that the tongue was displayed as a symbol of life force, which makes sense, as Tibetan and other Asian medicine tradition makes use of tongue diagnosis for state of health. (So do Westerners, in a less specific manner; “Say Ahhhhh”)

Anyone else know about this tradition, somewhat at odds with the basic explainations in this thread?

Another “tongue custom”: Laying the blade of a hot knife on a suspect’s tongue to prove honesty.

The logic was if you were lying, your mouth would be so dry your tongue wouldn’t be protected by enough saliva to keep it from burning you.

Q

I seem to recall a similar theory regarding the universal head jesture meaning ‘no’. The theory was that the head shake came from the infant turning his head away from the breast when he did not wish to eat. However, it has been so long since I read that, I have no idea *where *I read it.