Speakers of thousands of the world's languages are now abandoning their ancestral tongues at an unprecedented rate. What is lost when a language dies? And what are the implications?

"Languages are the repository of thousands of years of a people's science and art - from observations of ecological patterns to creation myths," says Swarthmore College linguist K. David Harrison, who spoke this weekend at the American Association for the Advancement of Science's annual meeting held this month in San Francisco.