moving right along...

The methods of Johanna Nichols in determining the regularity of a major split off a prime language stock involve correlations with language groups whose dates of isolation from their language roots are already known. For example some of the languages of New Guinea share a language stock with some of the languages of Australia: in particular, a grammar, called "concord classes", in which verbs and pronouns have to agree with nouns as to gender. Since the migration of mankind into Australia and New Guinea is dated by other means as occurring some 50,000 years ago this gives a top date for her to average 4,000 years increments of major deviations from major stocks.

I guess.

Anyway some of the features of the structural form of languages that she watches for as markers of 4,000 year changes she calls "ergativity" a feature of languages that uses special prefixes or suffixes to modify a verb. For example, the tense of an ergative verb may be indicated by a prefix other than a different form of the verb. Another example given is the Chinese and Navajo use of tone to modify or change the meaning of words. These, as well, are said to be very old and very entrenched structural forms to consider when monitoring changes as they relate to time.

Maybeso.

(Coming next: two waves of migration into the americas calibrated - sorta- by mitochondrial DNA.)