But a complex mix of economic, social, and cultural factors is now causing them to disappear at a faster pace.
Experts believe that more than half of the world's roughly 7,000 languages will vanish by the end of this century alone, at the rate of one language every two weeks.
"[When a language dies] what is primarily lost is the expression of a unique vision of what it means to be human," said David Crystal, honorary professor of linguistics at the University of Wales in the United Kingdom, and author of the book Language Death.
India's languages fall into at least seven major language families.
Of these, the Munda family—comprising at least a dozen tribal tongues spoken in eastern and central India—is among the most threatened.
"Definitely 10 to 20 percent of all Indian languages are in bad shape and on their death bed, but the Munda languages are the most vulnerable," said Panchanan Mohanty, a professor of linguistics at the University of Hyderabad, in the south Indian state of Andhra Pradesh.
Over the last few decades, linguists have analyzed several Munda languages such as the widely spoken Santali and Mundari, but the majority are poorly studied and sparsely documented. Many have yet to be rendered into computer typefaces, unable to cross the digital divide.
Fortunately, even the most obscure of the Munda tongues—such as that of the isolated Asur tribe in the eastern state of Jharkhand—still have at least a few thousand speakers, according to Ganesh Murmu, a linguist at Ranchi University in Jharkhand State.
"Even though many Munda languages are spoken by relatively smaller numbers of people, they are still the only languages spoken in the villages where these communities live," said Murmu, himself of tribal descent. (Murmu spoke to National Geographic News in Bengali.)
It's a situation that bodes well for the future, said the Enduring Voices team.
"Compared to some indigenous languages of North America that have only one or two speakers left, a lot of endangered languages in India still have between 2,000 to 10,000 speakers, so we can still imagine effective interventions to prevent extinction," said Harrison.
One such intervention is the creation of a digitized "talking dictionary" for Ho, a Munda language spoken by around a million people in the eastern states of Jharkhand, Orissa, and West Bengal.
Gregory Anderson, a member of the Enduring Voices team and a leading expert on the Munda languages, helped create an online Ho-English dictionary where users can click on words and hear recordings of native speakers pronouncing them.
Part of the overall revitalization strategy is to send graduate students to live in "hotspot" communities, to help continue language activities—from continued recordings to the publication of local-language stories, and creation of educational programs.
Anderson and Harrison have also visited the northeastern state of Arunachal Pradesh and rural Aka and Apatani communities there. Their team recorded samples of nearly half a dozen different local languages that could be used later for projects like the online dictionary. (Download a PDF of their full trip report.)
But members maintain that the success of such expeditions largely depends on the willingness of communities to preserve their own mother tongues.
With growing interest in language diversity, it may be possible for fading languages to get a new lease on life. Awareness of language preservation has steadily grown with the emergence of state-funded language programs, the potential to study minor languages at the college level, and new academic centers devoted to the study of endangered languages.
Ranchi University's Murmu believes most tribal communities will welcome the attention.
"Before, there was a feeling that if you speak a tribal language, you are in a lower social class," said Murmu. "But now there is pride. People are thinking: 'We too have status, we too have tradition, we too have identity.'"
"Just as people are doing so much to save the tiger or preserve ancient temples, it is as important to protect linguistic diversity, which is a part of India's cultural wealth and a monument to human genius," added Swarthmore's Harrison.
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