Linguists rebuilt a language no one has spoken in 5,000 years

No text in Proto-Indo-European has ever been found; it left no writing because it likely predates writing itself. Using the comparative method, linguists reconstructed thousands of its words and much of its grammar purely by systematically comparing sound patterns across its descendants, from English and Hindi to Russian and Persian. Reconstructed words are conventionally marked with an asterisk, like *wódr̥ for 'water'.

— Wikipedia contributors, Proto-Indo-European language — Comparative method reconstruction