To me, the cosmic question is: Even if contact were made with a sentient civiliations, and even if we could communicate in reasonable time, is there any evidence whatever, that even humans with completely different language on Earth could ever learn to understand each other via, say, morse code?

I am not talking about generalized ascertions that "mathematics is the answer," etc., etc., but whether it has ever been tried.

Given our inability to decode ancient middle Eastern languages until the Rosetta Stone was discovered, and our continued inability to decode Maya--all written by genetically similar humans--I think any claims that aliens could understand us requires some pretty strong proof.