Alright, you had some kind of primitive system for communicating certain "messages". It could be comparable to Morse code - two taps on the table means "me hungry", etc.
But I don't think that's related to people saying things like "70% of all communication is non-verbal". I just took it at face value, and tried to point out that it's not. It's just a comment that's tempting to throw around because it's kind of dramatic.
Instead of slapping an arbitrary percentage value on it, I'd be more comfortable saying "a considerable part of our communication is non-verbal", which it obviously is. 70% is just too high a percentage to be realistic.
Yes, language had to start somewhere, and because grunting and gesturing just isn't enough, it had to evolve to what we have now.