On the one end of the scale, we smile when we're happy and we cry when we're not. These things appear to be universal to the human race (and even typical among some of the great apes).
On the other end, you had to ask someone what it meant when they showed you a fist with their middle finger being the only one extended.
So my question is : To what degree is our non-verbal communication determined by genetics, and to what degree is it learned?
If I nod my head in a certain direction as if to say "go on, take it", would you know what I meant if you'd never seen anyone else do it before?