Last modified 14 Nov 07
All languages change during the course of time, and the longer the time period the greater the changes. When a language is culturally transmitted by speakers to their offspring over many generations, it can become so different that it is given a different name. Thus for example the Latin spoken in parts of the Iberian peninsula changed over time and became Spanish, Proto-Germanic became English in England, etc. A language whose speakers lose contact with one another can eventually evolve into numerous distinct languages. This is what happened with Proto-Indo-European, Latin, Proto-Germanic, and countless other languages spoken at various earlier periods in human history. Latin became Spanish, Portuguese, Italian, French, and a number of other languages spoken by groups currently without national status. We call such groups of languages related languages, because they are related to each other by virtue of paths of parent-to-offspring cultural transmission that trace back to a common source language.
Cultural transmission that happens between groups of adults, in which one group takes some of the words of the other group's language, is a different kind of relation called language contact. The term "related languages" is not used for this kind of situation.
Metaphorically, we can refer to the relation defined by a parent-child pattern of language transmission as genetic relationship of languages. The source language can be called the "ancestor language" or the "mother language", and the later languages deriving from it are called the "descendant languages" or the "daughter languages". Daughter languages are descended from the mother language. If there is only cultural contact as described above, the relationship is not one of genetic descent.
Genetically related languages can be closely related, or more distantly related, depending on how directly they trace back to a common source. Degree of relatedness can be represented by setting up a genetic classification of languages, shown in the form of a family tree in which daughter languages are plotted in relation to their mother languages, with direct connections representing closer relationship and indirect connections representing more distant relations. For example, English and German are closely related languages and would be right next to each other on the Indo-European family tree, because they are both directly descended from Proto-Germanic. English and Latin are also related, because they both trace back to the ancient Proto-Indo-European language, but they are much more distantly related because more time has passed between the source and the daughter languages and there were several language splits that happened in the meantime. The intermediate splits define groupings of more closely related languages like the Germanic languages and the Romance languages.
The family tree metaphor for language relationship is useful because it captures some similarities between language transmission and transmission of genes. Both involve transmission from generation to generation, but in one case it is cultural (the languages), the other biological (the genes).
The main problem of the family tree metaphor is that people often logically confuse language relationship with biological relationship, and think that people having the same language ancestry necessarily have the same biological ancestry and vice versa. This is obviously false, since a language can always be adopted by a people whose ancestors spoke other languages. Do you speak the language of your biological ancestors? Most Americans do not.
This problem can easily be avoided if we just recall that all culturally transmitted artifacts, technologies, and institutions are learned, not innate, including human languages; and that the family tree metaphor of language relationships is just that, a metaphor.
© 2005-2007 Suzanne Kemmer
Last modified 14 Nov 07