Dene-Yeniseian is a proposed genealogical link between the widespread North American language family Na-Dene (Athabaskan, Eyak, Tlingit) and Yeniseian in central Siberia, represented today by the critically endangered Ket and several documented extinct relatives. The Dene-Yeniseian hypothesis is an old idea, but since 2006 new evidence supporting it has been published in the form of shared morphological systems and a modest number of lexical cognates showing interlocking sound correspondences. Recent data from human genetics and folklore studies also increasingly indicate the plausibility of a prehistoric (probably Late Pleistocene) connection between populations in northwestern North America and the traditionally Yeniseian-speaking areas of south-central Siberia. At present, Dene-Yeniseian cannot be accepted as a proven language family until the purported evidence supporting the lexical and morphological correspondences between Yeniseian and Na-Dene is expanded and tested by further critical analysis and their relationship to Old World families such as Sino-Tibetan and Caucasian, as well as the isolate Burushaski (all earlier proposed as relatives of Yeniseian, and sometimes also of Na-Dene), becomes clearer.
“Altaic” is a common term applied by linguists to a number of language families, spread across Central Asia and the Far East and sharing a large, most likely non-coincidental, number of structural and morphemic similarities. At the onset of Altaic studies, these similarities were ascribed to the one-time existence of an ancestral language—“Proto-Altaic,” from which all these families are descended; circumstantial evidence and glottochronological calculations tentatively date this language to some time around the 6th–7th millennium bc, and suggest Southern Siberia or adjacent territories (hence the name “Altaic”) as the original homeland of its speakers. However, since the mid-20th century the dominant view in historical linguistics has shifted to that of an “Altaic Sprachbund” (diffusion area), implying that the families in question have not sprung from a common source, but rather have acquired their similarities over a long period of mutual linguistic contact. The bulk of “Altaic” has traditionally included such uncontroversial families as Turkic, Mongolic, and Manchu-Tungusic; additionally, Japanese (Japonic) and Korean are also frequently seen as potential members of the larger Altaic family (the entire five branches are sometimes referred to as “Macro-Altaic”). The debate over the nature of the relationship between the various units that constitute “Altaic,” sometimes referred to as “the Altaic controversy,” has been one of the most hotly debated topics in 20th-century historical linguistics and a major focal point of studies dealing with the prehistory of Central and East Eurasia. Supporters of “Proto-Altaic,” commonly known as “(pro-)Altaicists,” claim that only divergence from an original common ancestor can account for the observed regular phonetic correspondences and other structural similarities, whereas “anti-Altaicists,” without denying the existence of such similarities, insist that they do not belong to the “core” layers of the respective languages and are therefore better explained as results of lexical borrowing and other forms of areal linguistic contact. As a rule, “pro-Altaicists” claim that “Proto-Altaic” is as reconstructible by means of the classic comparative method as any uncontroversial linguistic family; in support of this view, they have produced several attempts to assemble large bodies of etymological evidence for the hypothesis, backed by systems of regular phonetic correspondences between compared languages. All of these, however, have been heavily criticized by “anti-Altaicists” for lack of methodological rigor, implausibility of proposed phonetic and/or semantic changes, and confusion of recent borrowings with items allegedly inherited from a common ancestor. Despite the validity of many of these objections, it remains unclear whether they are sufficient to completely discredit the hypothesis of a genetic connection between the various branches of “Altaic,” which continues to be actively supported by a small, but stable scholarly minority.
Different methods exist for classifying languages, depending on whether the task is to work out the relations among languages already known to be related—internal language classification—or whether the task is to establish that certain languages are related—external language classification. The comparative method in historical linguistics, developed during the latter part of the 19th century, represents one method for internal language classification; lexicostatistics, developed during the 1950s, represents another. Elements of lexicostatistics have been transformed and carried over into modern computational linguistic phylogenetics, and currently efforts are also being made to automate the comparative method. Recent years have seen rapid progress in the development of methods, tools, and resources for language classification. For instance, computational phylogenetic algorithms and software have made it possible to handle the classification of many languages using explicit models of language change, and data have been gathered for two thirds of the world’s language, allowing for rapid, exploratory classifications. There are also many open questions and venues for future research, for instance: What are the real-world counterparts to the nodes in a family tree structure? How can shortcomings in the traditional method of comparative historical linguistics be overcome? How can the understanding of the results that computational linguistic phylogenetics have to offer be improved? External language classification, a notoriously difficult task, has also benefitted from the advent of computational power. While, in the past, the simultaneous comparison of many languages for the purpose of discovering deep genealogical links was carried out in a haphazard fashion, leaving too much room for the effect of chance similarities to kick in, this sort of activity can now be done in a systematic, objective way on an unprecedented scale. The ways of producing final, convincing evidence for a deep genealogical relation, however, have not changed much. There is some room for improvement in this area, but even more room for improvement in the way that proposals for long-distance relations are evaluated.