, the technique of glottochronology
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 method is highly controversial and many linguists argue that there is no evidence that language change occurs at a steady rate. Glottochronological results are considered by many linguists to be 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.
- Robert Lees, The Basis of Glottochronology, Language, Vol. 29, No. 2., pp. 113-127.
- Andree Sjoberg and Gideon Sjoberg, Problems in Glottochronology, American Anthropologist, New Series, Vol. 58, No. 2., pp. 296-308.