Before the appearance of the Tungus in the Northern Siberia, Yukaghirs occupied a vast area from the Olenyok and Anabar Rivers in the West to the middle reaches of the Anadyr River in the East; the southern boundary of their settlement was the upper Lena River, the northern boundary was the Arctic Ocean. Currently Yukaghirs live in two isolated groups in the upper and lower reaches of the Kolyma River.
A map of the Yukaghir settlement
Source: Wikipedia. Yukaghir people https://ru.wikipedia.org/wiki/%D0%AE%D0%BA%D0%B0%D0%B3%D0%B8%D1%80%D1%8B