A language tree model is a means of visualizing the development of languages. Strictly speaking, this is the linguistic equivalent of a family tree. It is also fraught with the same problems of missing evidence and supposition to fill the gaps. The ultimate goal of the language tree model is to find the mother tongue of all humans, if such a language ever existed. The creation of such tree models is a part of language comparison and is the result of numerous studies into the origins and commonalities of languages across the world.
The model itself is often presented in a similar way to the family tree. Family trees tend to begin with a single couple and then record their children and their children’s children and so on until the tree reaches the modern day. While there are exceptions, the language tree model is more like a real tree, whereas instead of couplings, a branch will split into a number of other branches and so on until the tree reaches modern or terminus languages.
Exceptions include languages like English, which even in its old form, was an amalgam of a series of related languages such as Angle — modern day Angeln in southern Denmark —, Saxon, Jute and Frisian. In this sense, the branches split from proto-Germanic, then later merge to form English. The tree model of English is littered with dominant waves of language ideas from verb cases and sentence structures to how to pluralize nouns. For example, the subject-verb-object formation comes from West Saxon while the ‘s’ plural is from Northumbrian, a variety of Angle and Jute.
English falls into a good example of how a language family tree works. English is linked, via those various dialects and sub-languages, to Proto-Germanic. Also sprouting from the Proto-Germanic branch are the Nordic languages such as Swedish, Faroese and Icelandic; the Dutch languages such as Frisian, Dutch and Limburghish; and the High German languages from Austrian to High German. The Proto-Germanic language, in turn, branched off the Germano-Slavic branch of languages, which is a branch of the Proto-Indo-European language.
There are a number of causes of branching. These can include the relative isolation of communities, which develop their own distinct vocabularies and conventions, and also migration. Interacting and competing languages are a large influence on the fragmenting of proto-languages. Some languages like Serbo-Croatian splinter because one group uses one alphabet and the other uses a different one.
There are a number of problems with creating a language tree model. The biggest problem of all is the supposed proto-languages. In essence, there are no concrete proto-languages and any proto-language probably had dozens if not hundreds of dialects and sub-divisions.
Another factor undermining the language tree model is its failure to demonstrate the complexity of languages. As seen with English, languages are liable to pick up all manner of influences from other languages around them. Some languages can be mergers of different tongues such as the creation of Creole tongues in the Americas and in Africa. Others, like Hungarian, began as a mixture of the Mongolian languages such as Chinese, Korean and Japanese, but picked up all manner of influences along the way including Turkish and Latin.