That's a beautiful thought, thank you for taking the time to write that out. I agree with what you're saying, and see what you mean.

I suppose the one thing about human language is how specific it can be. You can never communicate the concept of a red sweater to a cow, unless there is one physically present. This "de-localization" of ideas is the main thing that sets human language apart, it seems. And if you look at a human brain, it has many more folds than a typical mammal brain. The intersection of folds on parts of the brain that are far in data/connectivity space, but close in physical proximity, results in neurons that fire together in patterns that don't necessarily go together. I think this is a useful tool that is the basis for language. But some people have extra physical overlap between brain sectors, and that results in synesthesia. Because if you look at a picture of a cat brain, it doesn't have the folds in the same way that overlap, so it can never truly make the mapping between a spoken phrase like "red sweater" and the actual red sweater. In that sense I think the cortex crossover is a bit of a superpower, and I think every human has it to some extent, and that's where the ability for language comes from. Specifically where the green part (temporal lobe, where language is stored) touches the pink part (frontal lobe) on this diagram, because those two lobes are mostly separate in function and operation but they do touch and overlap somewhat, and no other animal has that lobe-overlapping brain design feature: http://slideplayer.com/slide/4280537/14/images/1/Parietal+Lobe.jpg

Just a theory I have about synesthesia and language that I've been thinking about for a long time. I think this is the physical basis for it.