Darwin's Tongues: Languages, like Genes, Can Tell Evolutionary Tales

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Talk is cheap, but scientific value lurks in all that gab. Words cascading out of countless flapping gums contain secrets about the evolution of language that a new breed of researchers plan to expose with statistical tools borrowed from genetics.

For more than a century, traditional linguists have spent much of their time doing fieldwork-listening to native speakers to pick up on words with similar sounds, such as mother in English and madre in Spanish, and comparing how various tongues arrange subjects, verbs, objects and other grammatical elements into sentences. Such information has allowed investigators to group related languages into families and reconstruct ancestral forms of talk. But linguists generally agree that their methods can revive languages from no more than 10,000 years ago. Borrowing of words and grammar by speakers of neighboring languages, the researchers say, erases evolutionary signals from before that time.

Now a small contingent of researchers, many of them evolutionary biologists who typically have nothing to do with linguistics, are looking at language from in front of their computers, using mathematical techniques imported from the study of DNA to wring scenarios of language evolution out of huge amounts of comparative speech data.

These data analyzers assume that words and other language units change systematically as they are passed from one generation to the next, much the way genes do. Charles Darwin similarly argued in 1871 that languages, like biological species, have evolved into a series of related forms.

And in the same way that geneticists use computerized statistical approaches to put together humankind's family tree from the DNA of living people and a few long-dead individuals, these newcomers can generate family trees, called phylogenies, for languages. From existing data on numbers of speech sounds and types of grammatical structure, these phylogenies can point to ancient root languages and trace a path to today's tongues.

The new approach is making a splash--some would say a splatter--among mainstream linguists, who haven't exactly been anxiously waiting for advice from the fossils-and-genes crowd.

One recent study upends the traditional view that ancient languages did not evolve neatly, one into another and so on, arguing that modern tongues indeed contain telltale marks of how past languages moved across continents. Other results question the influential idea that grammar everywhere reflects innate properties of the human mind. Both investigations have appeared in high-profile science journals, drawing unprecedented publicity for explorations of speech sounds and word orders.

"Linguists spin a bit of a story with case studies of individual languages," says evolutionary biologist Russell Gray of the University of Auckland in New Zealand, a pioneer of the phylogenetic analysis of speech. "Statistical methods can now be used to examine languages rigorously and on a global scale."

Traditional language studies are still vital, he says, because they provide the massive amounts of speech and grammatical information needed for statistical breakdowns.

Talk of ages

Auckland's Quentin Atkinson, a psychologist and colleague of Gray's, stands in the eye of the phylogenetic storm. In a controversial paper in the April 15 Science, Atkinson concluded that because African languages have greater numbers of speech sounds than others, language probably originated in Africa. A parallel argument from evolutionary biology holds that greater numbers of DNA alterations in African populations reflect humankind's African roots.

Atkinson's study grew out of observations by other researchers that the number of sounds, or phonemes, employed in words declines as populations shrink and increases as populations enlarge. A succession of smaller and smaller groups migrating away from a larger founding population should thus lose more and more phonemes with increasing distance from the point of origin, Atkinson reasoned. …