A number of methods for carrying out language classification have been developed, ranging from simple inspection to computerised hypothesis testing.
[1] In particular, attempting to relate two reconstructed proto-languages by the comparative method has not generally produced results that have met with wide acceptance.
[citation needed] A number of methods based on statistical analysis of vocabulary have been developed to try and overcome this limitation, such as lexicostatistics and mass comparison.
In the twentieth century an alternative method, lexicostatistics, was developed, which is mainly associated with Morris Swadesh but is based on earlier work.
Swadesh used 100 (earlier 200) items that are assumed to be cognate (on the basis of phonetic similarity) in the languages being compared, though other lists have also been used.
An outgrowth of lexicostatistics is glottochronology, initially developed in the 1950s, which proposed a mathematical formula for establishing the date when two languages separated, based on percentage of a core vocabulary of culturally independent words.
In its simplest form a constant rate of change is assumed, though later versions allow variance but still fail to achieve reliability.
Greenberg suggested that the method is useful for preliminary grouping of languages known to be related as a first step toward more in-depth comparative analysis.
[4] However, since mass comparison eschews the establishment of regular changes, it is flatly rejected by the majority of historical linguists.
[6] Since the mid-1990s these more sophisticated tree- and network-based phylogenetic methods have been used to investigate the relationships between languages and to determine approximate dates for proto-languages.
These approaches have been challenged for their methodological problems, since without a reconstruction or at least a detailed list of phonological correspondences there can be no demonstration that two words in different languages are cognate.
[11] There are also strong, albeit areal not genetic, similarities between the Uralic and Altaic languages which provided an innocent basis for this theory.
[12] In the Dissertatio de origine gentium Americanarum (1625), the Dutch lawyer Hugo Grotius "proves" that the American Indians (Mohawks) speak a language (lingua Maquaasiorum) derived from Scandinavian languages (Grotius was on Sweden's payroll), supporting Swedish colonial pretensions in America.
The Frenchman Éloi Johanneau claimed in 1818 (Mélanges d'origines étymologiques et de questions grammaticales) that the Celtic language is the oldest, and the mother of all others.