In linguistics, the technique of glottochronology is used to estimate the time of divergence of two related languages. It is analogous to the use of C14 dating of organic materials in that a "lexical half-life" is estimated and used to extrapolate to the time the two languages being compared diverged. The method presumes that the basic vocabulary may be used as a sort of clock, on the assumption that basic vocabulary changes at a more-or-less constant rate through time. Morris Swadesh compiled a list of concepts for a basic vocabulary, the Swadesh list. The basic vocabulary was selected as to pick only concepts common to every human language and not subject to cultural changes. The method is highly controversial and many linguists argue that there is no evidence that language change occurs at a steady rate. In fact, there is evidence that unwritten languages tend to change more rapidly than written ones, and languages spoken in only a small area change faster than widely spoken ones. Many linguists thus discount glottochronological results as invalid.

Lexicostatistics involves measuring the percentage of cognates (that is, similar words with similar meanings in two languages where the similarity is attributable to descent from a common ancestral form in an ancestral language) in "basic word lists". The larger the percentage of cognates, the more recently the two languages being compared are presumed to have separated.

Bibliography

• Robert Lees(1953), The Basis of Glottochronology, Language, Vol. 29, No. 2., pp. 113-127.
• John McWhorter (2001), The Power of Babel. New York: Freeman. ISBN 0-7167-4473-2.
• Andree Sjoberg and Gideon Sjoberg (1956), Problems in Glottochronology, American Anthropologist , New Series, Vol. 58, No. 2., pp. 296-308.

Recent opinion suggests that the main problem with grottochronolgy (which is a sub-branch of lexicostatistics) is the insistence that languages change or lose their vocabulary at a constant rate. Swadesh calculated an average rate, which does of course exist, but this cannot be used as an absolute for every language.

External link

• Swadesh list http://en.wiktionary.org/wiki/Swadesh_list in Wiktionary.
• Discussion with some statistics http://linguistlist.org/issues/5/5-1168.html
• Indo-European lexicostatistical data http://www.ntu.edu.au/education/langs/ielex/HEADPAGE.html