Every two weeks the last elderly man or woman with full command of a particular language dies. At that rate, as many as 2500 native tongues will disappear by 2100.
"If we are going to lose half the world's language, that endangers our capacity to understand the genetic basis of language," said David Lightfoot, who heads the directorate of Social, Behavioural and Economic Sciences at the National Science Foundation.
Lightfoot is helping to spearhead a US government initiative to preserve some of these dying languages, believing each is a window into the human mind that can benefit the world at large.
The foundation recently joined the National Endowment for the Humanities in the effort to preserve languages.
The project has awarded US$4.4 million to 26 institutions and 13 individual scholars to investigate the status of 70 languages that are believed to be endangered and to help preserve them.
The project is now asking researchers to apply for additional grants, with the expectation that at least US$2 million a year will be available.
Some experts say there are up to 10,000 different languages left in the world; others put the estimate at thousands lower, depending on how many are characterized as dialects of another language.
Languages are not just words, linguists say, but a people's reflection of looking at the world.
Lightfoot gives the example of Guguyimadjir, spoken by the aboriginal people in the Australian state of Queensland.
They have no words for "left" or "right" but orient themselves and their world by the points of the compass, unlike most of us, who see things in relation to ourselves rather than to the world as a whole.
"Every language is an old-growth forest of the mind, a watershed of thought, an ecosystem of spiritual possibilities"
Wade Davis, anthropologist and National Geographic's explorer-in-residence
People in Brazil's Amazon rain forest who speak Piratapuyo say "The cake ate John" whereas English speakers would say "John ate the cake"; in other words, they put the object of a verb first and the subject last.
These peculiarities feed research on how the human mind works, how it perceives relations in space, how children learn complex languages so quickly and easily, Lightfoot said.
Such research will be aided by one method of saving languages: by recording their speech, analyzing their grammar, and preserving them digitally.
Other researchers are interested in a broader range of knowledge that is more difficult to save.
To do so requires encouraging younger people to learn their language from their elders, preserving not only the words themselves but unwritten traditions, arts, religion and more.
For example, plants used by traditional healers around the world have led to the discovery of new medicines, including aspirin.
Guguyimadjir is spoken by
aboriginals in an Australia state
Some small and declining tribe in Africa or in Papua New Guinea, a country where there are 820 languages among fewer than 5.5 million people, by one count, may know something about a plant that could help treat cancer or Alzheimer's.
For decades children in American Indian schools were discouraged from speaking tribal tongues and punished when they did.
That policy has long been abandoned, but generations were lost to many languages.
Anthony Woodbury, who heads the linguistic faculty of the University of Texas at Austin, suggests that if the motivation is strong enough, even a virtually dead language can be revived.
He points to Hebrew, a language learned for centuries only in its ancient written form.
A modern version is now a vital part of life in Israel. Another example: Irish has survived with political support.
At a conference sponsored by the two federal agencies, the National Science Foundation described how technology helps.
Scholars used to embalm a little-known language in a single book, available in a few research libraries.
Now data, including the actual sounds, will be widely and cheaply available on the internet, standardised so it can be compared with data on other languages.
"If we are going to lose half the world's language, that endangers our capacity to understand the genetic basis of language"
David Lightfoot, head of the US directorate of Social, Behavioural and Economic Sciences
Susan Penfield runs a project at the University of Arizona on two disappearing Indian languages along the Colorado River, where she has been working for more than 30 years.
One is Chemehuevi, a tongue related to that spoken by the ancient Aztecs in Mexico and Central America. She knows only five fluent speakers and told the conference she was especially proud of one, Johnny Hill Jr, who at 51 is comparatively young and also has a good command of English.
She told of training him and other fluent speakers in collecting data on the language, exploring aspects that have not yet been preserved and recording material digitally.
As Wade Davis, an anthropologist who roams the world as an explorer-in-residence at the National Geographic Society, wrote: "Every language is an old-growth forest of the mind, a watershed of thought, an ecosystem of spiritual possibilities."