I just finished reading 'Sapiens'. In the book, Harari mentions multiple times that "An ancient script was discovered and we came to know stuff about the civilization that lived in 2000 BCE"
How is this done? The last person who spoke 'language X' died 2000 years ago, we discover this new text now, how exactly do we know the semantics of the language? The grammar, the meaning of the words and letters?
There's always more to be said on the topic, but I wrote about the process for decipherment, with reference to cuneiform and Linear B, in Why haven't we deciphered Indus Valley Civilization script yet?
As I discuss in that post, you typically need knowledge of the language(s) (e.g. ancient Greek for Linear B, the Maya languages for Maya hieroglyphs) or a bilingual/multilingual inscription (e.g. the Rosetta Stone for Egyptian hieroglyphs and the Behistun inscription for cuneiform) for successful decipherment.