Written language doesn't exist for over 15,000 years.
Even though linguists have been able to trace language, or rather certain words, till this given period of 15,000 years ago, there isn't any evidence (at least for now) that this language had been used in written form. This is a language that is classified as proto-Euroasiatic language, and some words of it are still used in the same or similar form nowadays, but a written form has not been discovered of it.
