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Mass lexical comparison or mass comparison is a controversial method developed by the Joseph H. Greenberg to find genetic relationships among languages in the remote past, beyond the limits of the traditional comparative method, or in situations where there are too many languages to practically apply the latter without many generations of work.1 Traditional historical linguistics
1.1 The comparative method
Since the development of comparative linguistics in the 19th century, a linguist who claims that two languages are related, in the absence of historical evidence, is expected to back up that claim by presenting general rules that describe the differences between their lexicons, morphologies, and grammars. The procedure is described in detail in the Wikipedia article comparative method.
For instance, one could prove that Spanish is related to Italian by showing that many words of the former can be mapped to corresponding words of the latter by a relatively small set of replacement rules — such as change initial es- by s-, final -os by -i, etc. Many similar correspondences exist between the grammars of the two languages. Since those systematic correspondences are extremely unlikely to be random coincidences, the most likely explanation by far is that the two languages have evolved from a single ancestral tongue ( Latin, in this case.) Most pre-historical language groupings that are widely accepted today — such as the Indo-European, Algonquian, and Bantu families — have been proved in this way, although many - such as Niger-Congo, and until quite recently Afro-Asiatic and Sino-Tibetan - have not, and some families whose proponents claim to have proved them in this way (eg Nostratic) have not been widely accepted.
1.2 Limitations of the comparative method
However, besides systematic changes, languages are also subject to random mutations (such as borrowings from other languages, irregular inflections, compounding, and abbreviation) that affect one word at a time, or small subsets of words. For example, Spanish perro, which does not come from Latin, cannot be rule-mapped to its Italian equivalent cane.
As those sporadic changes accumulate, they will increasingly obscure the systematic ones — just as enough dirt and scratches on a photograph will eventually make the face unrecognizable. Given the rate at which those random mutations occur, they are expected to obliterate any systematic similarities between languages that have split off more than 10,000 years ago. Considering that humans probably have been speaking fully developed languages since at least 60,000 years ago (when Australia was first populated), it is hardly surprising that many languages and language families still have no known relationship with other groups.
2 Mass lexical comparison
2.1 Lexical similarity
In an effort to extend comparative linguistics beyond its present limits, and arrive at his broad super-family groupings, Greenberg invented a new statistical method, mass lexical comparison. In this method, one simply compares a large sample of words from one language with its equivalents in the other language , looking for similar sound patterns. Thus, for example, Spanish cabeza and Italian capo are similar to the extent that both contain the same consonantA consonant is a sound in spoken language that is characterized by a constriction or closure at one or more points along the vocal tract. The word consonant comes from Latin meaning "sounding with" or "sounding together", the idea being that consonants do sound [k], similar vowelIn phonetics, a vowel is a sound in spoken language that is characterized by an open configuration of the vocal tract, in contrast to consonants, which are characterized by a constriction or closure at one or more points along the vocal tract. The word vo sounds [a], and similar consonants [b], [p], in the same sequence.
Departing from the traditional criterion, Greenberg did not look for any systematic trend in these similarities, trusting that a sufficiently large percentage of sufficiently similar pairs among the samples would be enough to prove a common origin for the two languages. This assumption is valid in principle, because is expected to be higher for languages that have split off more recently, and decrease as the split recedes into the past. The difficult part is deciding what constitutes "sufficient" similarity.
