Internal reconstruction

Internal reconstruction is a method of reconstructing an earlier state in a language's history using only language-internal evidence of the language in question. The comparative method compares variations between languages, such as in sets of cognates, under the assumption that they descend from a single proto-language, but internal reconstruction compares variant forms within a single language under the assumption that they descend from a single, regular form. For example, they could take the form of allomorphs of the same morpheme. The basic premise of internal reconstruction is that a meaning-bearing element that alternates between two or more similar forms in different environments was probably once a single form into which alternation has been introduced by the usual mechanisms of sound change and analogy. Language forms that are reconstructed by internal reconstruction are denoted with the pre- prefix, as in Pre-Old Japanese, like the use of proto- to indicate a language reconstructed by means of the comparative method, as in Proto-Indo-European. (However, the pre- prefix is sometimes used for an unattested prior stage of a language, without reference to internal reconstruction.) It is possible to apply internal reconstruction even to proto-languages reconstructed by the comparative method. For example, performing internal reconstruction on Proto-Mayan would yield Pre-Proto-Mayan. In some cases, it is also desirable to use internal reconstruction to uncover an earlier form of various languages and then submit those pre- languages to the comparative method. Care must be taken, however, because internal reconstruction performed on languages before the comparative method is applied can remove significant evidence of the earlier state of the language and thus reduce the accuracy of the reconstructed proto-language. When undertaking a comparative study of an underanalyzed language family, one should understand its systems of alternations, if any, before one tackles the greater complexities of analyzing entire linguistic structures.