More use, less change

Vox Populi

An occasional Jurisdynamics series on language and linguistic diversity

It has been nearly a year since I last wrote in my Vox Populi series, in a post called Heritage speakers, but human language, my first and favorite intellectual paramour, has always waited for me.

By way of the New York Times' weekly science section, I've learned of this fascinating new article:

Mark Pagel, Quentin D. Atkinson & Andrew Meade, Frequency of word-use predicts rates of lexical evolution throughout Indo-European history, 449 Nature 717-720 (11 October 2007) (doi:10.1038/nature06176; Received 30 April 2007; Accepted 17 August 2007)

The geographic distribution of the Indo-European languages (click the image or here to enlarge).

Greek speakers say ουρ, Germans schwanz and the French queue to describe what English speakers call a tail, but all of these languages use a related form of two to describe the number after one. Among more than 100 Indo-European languages and dialects, the words for some meanings (such as tail) evolve rapidly, being expressed across languages by dozens of unrelated words, while others evolve much more slowly -- such as the number two, for which all Indo-European language speakers use the same related word-form. No general linguistic mechanism has been advanced to explain this striking variation in rates of lexical replacement among meanings. Here we use four large and divergent language corpora (English, Spanish, Russian and Greek) and a comparative database of 200 fundamental vocabulary meanings in 87 Indo-European languages to show that the frequency with which these words are used in modern language predicts their rate of replacement over thousands of years of Indo-European language evolution. Across all 200 meanings, frequently used words evolve at slower rates and infrequently used words evolve more rapidly. This relationship holds separately and identically across parts of speech for each of the four language corpora, and accounts for approximately 50% of the variation in historical rates of lexical replacement. We propose that the frequency with which specific words are used in everyday language exerts a general and law-like influence on their rates of evolution. Our findings are consistent with social models of word change that emphasize the role of selection, and suggest that owing to the ways that humans use language, some words will evolve slowly and others rapidly across all languages.

The power of this article is instantly apparent to any careful student of diachronic linguistics and evolutionary biology. Indeed, it unifies the two fields. George Kingsley Zipf, meet Charles Darwin. The same process of random mutation, natural selection, sexual selection, and genetic drift that defines biological evolution also explains Zipf's law.

In practical terms, this phenomenon explains how any perceptive speaker of an Indo-European language can make astonishing headway in a previously unfamiliar Indo-European language simply by focusing on these classes of words:

• Numbers
• Body parts
• Animals
• Family members

Once again, in science as elsewhere, somehow the vital connection is made: