vocabulary items will negate individual inaccuracies; thus, they can be used to determine relatedness but not to determine the proto-language. History The earliest method of this type was the comparative method, which was developed over many years, culminating in the nineteenth century. This uses a long word list and detailed study. However, it has been criticized for example as subjective, informal, and lacking testability. The comparative method uses information from two or more languages and allows reconstruction of the ancestral language. The method of internal reconstruction uses only a single language, with comparison of word variants, to perform the same function. Internal reconstruction is more resistant to interference but usually has a limited available base of utilizable words and is able to reconstruct only certain changes (those that have left traces as morphophonological variations). In the twentieth century an alternative method, lexicostatistics, was developed, which is mainly associated with Morris Swadesh but is based on earlier work. This uses a short word list of basic vocabulary in the various languages for comparisons. 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. Distance measures are derived by examination of language pairs but such methods reduce the information. 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. Glottochronology has met with mounting scepticism, and is seldom applied today. Dating estimates can now be generated by computerised methods that have fewer restrictions, calculating rates from the data. However, no mathematical means of producing proto-language split-times on the basis of lexical retention has been proven reliable. Another controversial method, developed by Joseph Greenberg, is mass comparison. The method, which disavows any ability to date developments, aims simply to show which languages are more and less close to each other. 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. However, since mass comparison eschews the establishment of regular changes, it is flatly rejected by the majority of historical linguists. Recently,