[ivape]

Why would a human need to develop the ability to convince others if truth should be enough? One would have to make the argument that convincing others and oneself involves things that are not true to at least one party (as far as they know). I don't know why a species would develop misunderstanding if truth is always involved. If emotions/perception are the things that create misunderstanding, then I can see the argument for language as necessary to fix misunderstanding in the group. On some level, nature thought it correct to fix misunderstanding on a species level.

[justonceokay]

The problem with this line of reasoning is that “truth” is a word, and therefore not “enough” be definition of not being a physical thing in the world. Without communication there can be no lies, so truth doesnt mean anything.

If by “truth” you mean more like Kants “the thing in itself”, then the problem there is we need abstraction. If I show you how to make an arrowhead, somehow I need to convey that you can follow the same process with your own piece of flint, and that they are both arrowheads. Without any language abstraction my arrowhead and your arrowhead are just two different rocks with no relation to each other.