"...they go back so far that the great apes share some of them."

Like beating your chest at the "I Confess".

........................

Maggie Thatcher used to do "keeps (his) elbow down close to (his) ribs, hand raised up" as a way of silencing interviewers. It works quite well in other situations - for example, when you don't want to be stopped by someone inspecting tickets, or are trying to go somewhere that is sort of not open to the public. Not always, but surprisingly often - it more or less says "this is all sorted out already - don't delay me".

If I was a ticket inspector, I'd be inclined to insist on a strip search of anyone who tried it on me. (What a horrible thought with Maggie Thatcher...).

It's also something glove puppets go in for, for reasons of anatomy.