He mapped the glottochronology of the Romance languages.    From Wordnet, Princeton University. 

Note 9: The evidence supporting the continued value of glottochronology is most convincingly seen when again and again there are correlations found between archaeology and linguistic based conclusions.    From Wordnik.com.  [Societies, Religion, and History: Central East Tanzanians and the World They Created, c. 200 BCE to 1800 CE] Reference

(1909-67) to calculate the degree of time depth behind divergent members of a family or of an area through glottochronology, that is, by assuming constancy for the rate with which “basic” vocabulary is replaced.    From Wordnik.com.  [LINGUISTICS] Reference

Historical linguistics, in particular, has provided a method for measuring change in language, called glottochronology.    From Wordnik.com.  [D. Africa, 500-1500] Reference

The reason for the criticism appears to stem largely from a mix-up about what the tool of glottochronology claims to do.    From Wordnik.com.  [Societies, Religion, and History: Central East Tanzanians and the World They Created, c. 200 BCE to 1800 CE] Reference

Obviously this is not the whole picture, but I think it helps with the relative glottochronology between a few important dialect groups.    From Wordnik.com.  [Winter's Law in Balto-Slavic, "Hybrid Theory" and phonation - Part 2] Reference

Ehret's view is that both the detractors of glottochronology and many of its early supporters misunderstood it as a phenomenon involving regular and predictable change.    From Wordnik.com.  [Societies, Religion, and History: Central East Tanzanians and the World They Created, c. 200 BCE to 1800 CE] Reference

It is important to recognize, however, that many linguists do not agree on the validity and accuracy of glottochronology and lexicostatistics in determining linguistic diffusion.    From Wordnik.com.  [Are you related to the Aztecs?] Reference

As to the fact that the Ute and the Aztec spoke languages derived from the same root-language, you might want to introduce your readers to glottochronology, the science of dating origins by language attrition.    From Wordnik.com.  [Centennial]

What glottochronology adds to this is the ability to assign very rough dating estimates to the stratigraphy. 7 Having these estimates allows us to compare them with conclusions drawn from archaeological research.    From Wordnik.com.  [Societies, Religion, and History: Central East Tanzanians and the World They Created, c. 200 BCE to 1800 CE] Reference

27Just as there are debates waged on the use of dendrogram illustrations, there are also uncertainties surrounding the use of glottochronology.    From Wordnik.com.  [Societies, Religion, and History: Central East Tanzanians and the World They Created, c. 200 BCE to 1800 CE] Reference

6 In other words, glottochronology never suggests that all languages substitute core vocabulary at a fixed rate, or that they substitute the same words.    From Wordnik.com.  [Societies, Religion, and History: Central East Tanzanians and the World They Created, c. 200 BCE to 1800 CE] Reference

Some 20th-century introductions into linguistic vocabulary make use of the root: we find Bloomfield's glosseme and Hjelmslev's glossematics; the isoglottic line of linguistic geography; and glottochronology, Swadesh's system for dating the divergence of linguistic family members.    From Wordnik.com.  [VERBATIM: The Language Quarterly Vol X No 4] Reference

26The dendrogram provides a constructive visual representation of the pathways of language divergence, but the application of an additional linguistic tool, glottochronology, provides a useful way for historians to hypothesize relative approximations for the likely dating of language divergence over time.    From Wordnik.com.  [Societies, Religion, and History: Central East Tanzanians and the World They Created, c. 200 BCE to 1800 CE] Reference