Then, it was Swadesh yet who warned that comparison of vocabularies can’t be proof of genetic relationship of languages and some other methods should be used for it, i.e.: analysis of structures. Swadesh method is method of estimation of approximate time of divergence of languages which have been already proved to be relatives. However, Swadesh’s warning has been well forgotten. Also we should keep in mind that even so called basic lexicon is actually culturally determined (Hoijer 1956) and borrowings can be inside it (above considered example of Japanese and Cantonese).
Moreover, we should keep in mind the fact that there are thousands of languages which history is completely unknown and which are described only in their current phase and so there is no ability to distinguish borrowings in their lexicon and so it’s completely impossible to say anything about their genetic relationship basing on methodology of comparison of lexis.
Methodology that ignores structural/grammatical issues allows different scholars to make completely different conclusions about the same language, for instance: Sumerian is thought to be a relative of Kartvelian stock (Nicholas Marr), of Uralic stock (Simo Parpola), of Sino-Tibetan (Jan Braun), of Mon-Khmer (Igor M. Diakonoff) or even of Basque (Aleksi Sahala). Another notable example is Ainu that is attributed to Altaic (James Patrie), to Austronesian (Murayama Shichirō), to Mon-Khmer (Alexander Vovin)6. The most notable fact is that all such attempts coexist and all are considered by public as rather reliable in the same time, obviously it looks much a like a plot for a vaudeville sketch rather than a serious matter of a science.
Different methods can lead to different conclusions but if people use same methodology they supposedly are expected to make same conclusions about the same material, however, we don’t see it; it means only that methodology based on comparison of lexis isn’t relevant for comparative linguistics.
Also a weird issue is that such lexical methodology has never been tested in an appropriate way. Being asked “why you came to the conclusion that it is possible to conclude something about certain languages genetic relationship basing on comparison of lexis only?” megalocomparativists usually answer “morphology doesn’t matter” and don’t explain how they came to such conclusion; they actually look much alike adepts of a religion but not alike scientists since science always supposes experiments and verifications while statements “it is so because it is so” obviously don’t belong to the field of science but actually are statements of a religion.