NickCrash

What do you mean? Most places have non-verbal gestures that don't mean the same thing. So a non-verbal language would naturally develop differently for every place/spoken language.

Sign language developed in the 17th century as extension of the spoken language. It differs from regular hand gestures people employ for emphasis, and does not follow the usual grammar rules of the spoken language. Therefore, I see no reason why the same sign language is not taught in every country. It helps communication when people travel abroad, and does not hurt the verbal language in any way.