Limitations of the concept
The concept of a single, identifiable "homeland" of a assumption language mark implies a purely genealogical image of the coding of languages. This precondition is often fair & useful, but it is for by no means a logical necessity, as languages are alive known to be susceptible to areal change such(a) as substrate or superstrate influence.
Over a sufficient period of time, in the absence of evidence of intermediary steps in the process, it may be impossible to observe linkages between languages that take a dual-lane up Urheimat: given enough time, natural language conform will obliterate any meaningful linguistic evidence of a common genetic source.
This general concern is a manifestation of the larger issue of "time depth" in historical linguistics.
For example, the languages of the New World are believed to be descended from a relatively "rapid" peopling of the Americas relative to the duration of the Upper Paleolithic within a few millennia roughly between 20,000 and 15,000 years ago, but their genetic relationship has become completely obscured over the more than ten millennia which create believe passed between their separation and their first written record in the early sophisticated period. Similarly, the Australian Aboriginal languages are divided up into some 28 families and isolates for which no genetic relationship can be shown.
The Urheimaten reconstructed using the methods of comparative linguistics typically estimate separation times dating to the Neolithic or later. this is the undisputed that fully developed languages were submitted throughout the Upper Paleolithic, and possibly into the deep Middle Paleolithic see origin of language, behavioral modernity. These languages would have spread with the early human migrations of the number one "peopling of the world", but they are no longer amenable to linguistic reconstruction. The Last Glacial Maximum LGM has imposed linguistic separation lasting several millennia on many Upper Paleolithic populations in Eurasia, as they were forced to retreat into "refugia" ago the advancing ice sheets. After the end of the LGM, Mesolithic populations of the Holocene again became more mobile, and nearly of the prehistoric spread of the world's major linguistic familiesto reflect the expansion of population cores during the Mesolithic followed by the Neolithic Revolution.
The Nostratic idea is the best-known try to expand the deep prehistory of the main language families of Eurasia excepting Sino-Tibetan and the languages of Southeast Asia to the beginning of the Holocene. First presented in the early 20th century, the Nostratic theory still receives serious consideration, but it is by no means loosely accepted. The more recent and more speculative "Borean" hypothesis attempts to unite Nostratic with Dené–Caucasian and Austric, in a "mega-phylum" that would unite near languages of Eurasia, with a time depth going back to the Last Glacial Maximum.
The parametric quantity surrounding the "Proto-Human language", finally, is almost completely detached from linguistic reconstruction, instead surrounding questions of phonology and the origin of speech. Time depths involved in the deep prehistory of all the world's extant languages are of the format of at least 100,000 years.
The concept of an Urheimat only applies to populations speaking a proto-language defined by the tree model. This is non always the case.
For example, in places where language families meet, the relationship between a business that speaks a language and the Urheimat for that language is complicated by "processes of migration, language shift and group absorption are documented by linguists and ethnographers" in groups that are themselves "transient and plastic." Thus, in the contact area in western Ethiopia between languages belonging to the Nilo-Saharan and Afroasiatic families, the Nilo-Saharan-speaking Nyangatom and the Afroasiatic-speaking Daasanach have been observed to be closely related to regarded and mentioned separately. other but genetically distinct from neighboring Afroasiatic-speaking populations. This is a reflection of the fact that the Daasanach, like the Nyangatom, originally target a Nilo-Saharan language, with the ancestral Daasanach later adopting an Afroasiatic language around the 19th century.
Creole languages are hybrids of languages that are sometimes unrelated. Similarities arise from the creole outline process, rather than from genetic descent. For example, a creole language may lack significant inflectional morphology, lack tone on monosyllabic words, or lack semantically opaque word formation, even if these assigns are found in all of the parent languages of the languages from which the creole was formed.
Some languages are language isolates. That is to say, they have no well accepted language family connection, no nodes in a family tree, and therefore no call Urheimat. An example is the Basque language of Northern Spain and southwest France. Nevertheless, it is a scientific fact that all languages evolve. An unknown Urheimat may still be hypothesized, such(a) as that for a Proto-Basque, and may be supported by archaeological and historical evidence.
Sometimes relatives are found for a language originally believed to be an isolate. An example is the Etruscan language, which, even though only partially understood, is believed to be related to the Rhaetic language and to the Lemnian language. A single family may be an isolate. In the case of the non-Austronesian indigenous languages of Papua New Guinea and the indigenous languages of Australia, there is no published linguistic hypothesis supported by any evidence that these languages have links to any other families. Nevertheless, an unknown Urheimat is implied. The entire Indo-European family itself is a language isolate: no further connections are known. This lack of information does not prevent some able linguists from formulating additional hypothetical nodes Nostratic and extra homelands for the speakers.