This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
Isolates gathers three languages the atlas records as related to nothing else known, each a survivor of a linguistic landscape the surrounding language families erased.
Basque is the last surviving language of western Europe from before the Indo-European expansion, spoken in the western Pyrenees, with no demonstrated relative anywhere; proposals linking it to the Caucasian languages, to Iberian and to a wider Vasconic substrate have all been made and none accepted. Sumerian is the language of the earliest cities and the earliest writing, spoken in southern Iraq and related to nothing else known; Akkadian replaced it in speech in the early second millennium BCE, yet Sumerian carried on for two further millennia as the language of ritual, of the scribal curriculum and of a large body of hymns, an afterlife as a sacred and scholarly language rather than a spoken one. Ainu, historically spoken on Hokkaido and, in now extinct dialects, on Sakhalin and the Kuril Islands, is unrelated to Japanese or to any other known family; suppressed under Meiji era assimilation policy, it survives today with only a handful of fully fluent native speakers and is classified by UNESCO as critically endangered.
What unites the three is only the negative fact of isolation, not a shared history; a family with no known relatives is what a language looks like after every relative it once had has vanished from the record, or the branch itself never had one to begin with.