I would say the palm on the bent arm looks like it has sexual connotations (and possibly sodomy) which is similar to the fuck off, or more closely 'fuck you' with the raised middle finger. ALthough it really means 'I fuck you' it has more to do with power and dominance than sex, just like animals mounting each other to show dominance. (Desmond Morris has done books, and tv shows on the subject and it is quite fascinating just how much meaning there is associated with gestures and how it differs around the world.)

I noticed when I lived in Japan, that when someone waves to summon you the hand faces down (instead of up which would be really rude - similar to curling the index finger as if calling a child.

some other gestures: the hitch hiking thumb, in one part of south east asia it means 'wheres the nearest bathroom'

a friend who lived in South America noticed that when they say 'I was this small' and hold out their hand to indicate height they have their palm up (instead of down).

there is the evil eye: hand forward with index and small finger up and thumb holding down the middle and ring. (some kind of curse)

the cuckold; placing of the thumb toward the nose and fingers spread out.

the greeks use the hands making an upward motion from closed fist to open palm (as if throwing at someone) supposedly excrement.

my favorite: the placing of thumb and fingers in a circle as if holding a glass but thumb and index touching, and placing it on the forehead and making an outward motion with the hand. (translation Dickhead) this is used as a car signaling gesture (but dont hit the windshield). THis is more british than north am.

(I for one like the archer (agincourt/crecy) origins of the two finger salute as it is only common to britain, although the aussie version (i think) is with two fingers but together.)

WHat gets me is the space people need-; those who grow up in more congested areas tend to move in closer in conversation than those who live in the country. petr