Languages aren't concrete things. They are historical chains of interacting cause and effect where a person learns to speak from a community then joins the comm

Languages aren't concrete things. They are historical chains of interacting cause and effect where a person learns to speak from a community then joins the community and in so doing propagates the language to others. Asking about the "age" of a language doesn't really make any sense, except for constructed languages like Esperanto, and even those aren't really denovo because they inevitably are created by people who already spoke another language. A better question is what language has the longest period of mutual comprehensibility, e.g. if you took a speaker from time A to time B. As an English speaker, I could talk to Shakespeare with some mild accommodations, but I would have a lot of trouble talking to Chaucer. For written languages, the period of mutual comprehensibility can end up being thousands of years long because people in later generations are trained on the earlier texts, but for spoken languages, things tend to break up after a few hundred years. The best chance for a spoken language to maintain intelligibility is to have some kind of religious community that insists on preserving the old dialect, like Sanskrit (where there is a well preserved canon of pronunciation), Classical Arabic (Quran recitation), Hebrew, Latin, etc.