system
Given the following post, respond as if you're commenting on Reddit:
human
How do scientists decipher a language with no known speakers?

How do scientists decipher ancient languages (like a carving, insription, scripture or whatever) with no known speakers? Can they figure out the sounds would relate to each visual symbol? What if there aren't any languages that were verbally or visually similar (as if none evolved into or from it and it was "unique")? What are the main problems scientists face while trying to decipher an unknown language?
gpt
Sometimes you can find a document in both an unknown and known language. But often you have to resort to cribs (phrases that you know will appear in the text). For example you know a text was issued by a king, you can guess that the word king and the king's name appear. It's basically a known plaintext attack.

Sounds? Not sure how they'd figure that out.