Proto-Inuit-Yupik-Unangan or Proto-Eskimo-Aleut was the common ancestor of the Eskimo languages and Aleut. Its existence is known through similarities in Eskimo and Aleut. The existence of Proto-Eskimo-Aleut is generally accepted among linguists. It was for a long time true that no linguistic reconstruction of Proto-Eskimo-Aleut had yet been produced, as stated by Bomhard (2008:209). Such a reconstruction was offered by Knut Bergsland in 1986. Michael Fortescue (1998:124-125) has offered another version of this system, largely based on the reconstruction of Proto-Eskimo in the Comparative Eskimo Dictionary he co-authored with Steven Jacobson and Lawrence Kaplan (1994:xi).
Fortescue reconstructs the phoneme inventory of Proto-Eskimo-Aleut as follows:
There are no generally accepted relations between Proto-Eskimo-Aleut and other language families. A substantial case for a genetic relationship between Proto-Eskimo-Aleut and several languages of northern Eurasia was published by Michael Fortescue in 1998 in Language Relations across Bering Strait (see Uralo-Siberian languages).