A genealogical connection between the Tlingit, Eyak and Athabaskan languages was suggested early in the 19th century, but not universally accepted until much later.
Haida, with 15 fluent speakers (M. Krauss, 1995), was originally linked to Tlingit by
Franz Boas in 1894. Both Haida and Tlingit were then connected to Athabaskan by Edward Sapir in 1915. Linguists such as
Lyle Campbell today consider the evidence inconclusive. They have classified Haida as a
language isolate. In order to emphasise the exclusion of Haida, Campbell refers to the language family as
Athabaskan–Eyak–Tlingit rather than
Na-Dene. In 2010 Jeff Leer published extensive primary materials on what he calls
PAET (Proto-Athabaskan–Eyak–Tlingit).
Dene–Yeniseian Connections between the Na-Dené family and the Siberian languages have occasionally been proposed, possibly as early as 1923. As evidence has mounted that
the Americas were populated by people who crossed the Bering Sea land bridge from Siberia, such proposals have grown more historically plausible. The best-known of these proposals is the
Dené–Yeniseian languages hypothesis from
Edward Vajda and others. Under this hypothesis, the Na-Dené languages might be related to the
Yeniseian (or Yeniseic) languages of
Siberia, the only living representative of which is the
Ket language. The core motivations for the proposed family connection are homologies in verb prefixes and a systematic correspondence between the distribution of Ket tones and consonant articulations found in Athabaskan–Eyak–Tlingit.
Sino–Tibetan A link between the Na–Dene languages and Sino–Tibetan languages, known as
Sino–Dene, was first proposed by
Edward Sapir. Around 1920, Sapir became convinced that Na–Dene was more closely related to Sino–Tibetan than to other American families. He wrote a series of letters to
Alfred Kroeber where he enthusiastically spoke of a connection between Na–Dene and "Indo–Chinese". In 1925, a supporting article summarizing his thoughts, albeit not written by him, entitled "The Similarities of Chinese and Indian Languages", was published in Science Supplements. The Sino–Dene hypothesis never gained foothold in the
United States outside of Sapir's circle, though it was later revitalized by Robert Shafer (1952, 1957, 1969) and
Morris Swadesh (1952, 1965).
Alfredo Trombetti, who was the first to propose a relationship between the Yeniseian and Na–Dene language families (1923), had also independently discovered the idea of Sino–Dene (1923, 1925). A 2023 analysis by
David Bradley using the standard techniques of comparative linguistics supports a distant genetic link between the Sino–Tibetan, Na–Dene, and Yeniseian language families. Bradley argues that any similarities Sino–Tibetan shares with other language families of the East Asia area such as
Hmong–Mien,
Altaic (which is a
sprachbund),
Austroasiatic,
Kra–Dai, and
Austronesian came through contact; but as there has been no recent contact between the Sino–Tibetan, Na–Dene, and Yeniseian language families, any similarities these groups share must be residual.
Other proposals According to
Joseph Greenberg's controversial classification of the languages of Native North America, Na-Dene (including Haida) is one of the three main groups of Native languages spoken in the Americas. Contemporary supporters of Greenberg's theory, such as
Merritt Ruhlen, have suggested that the Na-Dene language family represents a distinct migration of people from
Asia into the New World that occurred six to eight thousand years ago, placing it around four thousand years later than the previous migration into the Americas by
Amerind speakers; this remains an unproven hypothesis. Ruhlen speculates that the Na-Dene speakers may have arrived in boats, initially settling near the
Haida Gwaii, now in
British Columbia, Canada. Bouda, in various publications in the 1930s through the 1950s, described a linguistic network that (besides Yeniseian and Sino-Tibetan) also included
Caucasian, and
Burushaski, some forms of which have gone by the name of Sino-Caucasian. The works of R. Bleichsteiner and O.G. Tailleur, the late
Sergei A. Starostin and
Sergei L. Nikolayev have sought to confirm these connections. Others who have developed the hypothesis, often expanded to Dene–Caucasian, include J.D. Bengtson, V. Blažek,
J.H. Greenberg (with
M. Ruhlen), and M. Ruhlen.
George Starostin continues his father's work in Yeniseian, Sino-Caucasian and other fields. This theory is very controversial or viewed as obsolete by other linguists. == Genetics and dispersal ==