High Quality Content by WIKIPEDIA articles! In historical linguistics, the Tree Model (German Stammbaumtheorie), or more recently the Genetic or Cladistic Model, is a model of language change described by an analogy with the concept of family tree. In this scientific metaphor, the family members are languages, the family is a language family and the birth kinships of people are genetic relationships between languages. A language that can therefore be a parent or mother language or a daughter language (fathers and sons are not in the metaphor). Languages can have lines of descent, can be cognate and can be "related." In this metaphor, languages are treated as objects sui generis ("of their own kind"). The biological or sociological circumstances of the speakers are completely irrelevant. They may be biologically related or unrelated, kin or not, but are ignored indifferently by the metaphor.