Yuki

Yuki is the language of the Yuki people of northern California, spoken in Round Valley and the upper Eel River. Together with Wappo of the Napa Valley it forms the small Yukian family, counted among the oldest linguistic strata in California, perhaps established before the spread of Hokan and Penutian speakers; the two languages are thought to have diverged in the course of the second millennium BCE.

Yuki had three dialects, Valley Yuki, Huchnom and Coast Yuki, matching the people's three divisions. Its most striking feature was a base-four counting system, reckoned on the spaces between the fingers rather than on the fingers themselves, and the language had no writing system.