The ancestor of hundreds of languages, including English, Italian, Russian, Farsi, and Punjabi; the last speaker of Yahi; the last speaker of Yaghan; and nests to revive endangered languages.
Cristina Calderón is the last native speaker of Yaghan; when she dies, the language may die with her.
Ishi was the last speaker of Yahi. He died nameless because no-one else alive could formally introduce him.
Proto-Indo-European is the ancestor of many languages of Europe, India, and elsewhere – and we have some good guesses about what it sounded like.
If you want to resurrect an endangered language, it’s best to start young.