Regarding visual communication, I think you downsell posturing, gesturing and facial expressions a little. They may not be as high bandwidth as talking but they are very low latency and pretty stealthy if necessary.
Well, there is sign language, so I guess you're right. It would be interesting to see how high bandwidth gesturing can be compared to speaking.
I thought about this some more and I think the prevalence of making sounds rather than gesturing etc. is due to sound being a broadcasting mechanism that works over long distances and without line of sight.
Visually indicating that you've claimed some territory is pretty hard.
Well, there is sign language, so I guess you're right. It would be interesting to see how high bandwidth gesturing can be compared to speaking.
I thought about this some more and I think the prevalence of making sounds rather than gesturing etc. is due to sound being a broadcasting mechanism that works over long distances and without line of sight.
Visually indicating that you've claimed some territory is pretty hard.