 The theory of an Indo-European—Ainu relation was popular until 1960, later linguists did not follow the theory any more and concentrated on more local language families.Tambotsev (2008) proposes that Ainu is typologically most similar to Native American languages and suggests that further research is needed to establish a genetic relationship between these languages.Until the 20th century, Ainu language was also spoken throughout the southern half of the island of Sakhalin and by small numbers of people in the Kuril Islands.