Video: "The linguistic genius of babies" by Patricia Kuhl at TED Talk. http://www.ted.com/talks/patricia_kuhl_the_linguistic_genius_of_babies
What does preserving a language really means? Record it and preserve it in archival? No. Teach a language to others? No.
To truly preserve a language is to speak (manually or vocally, depending on which language it is) to babies in a native environment, as shown an example in the video: a mother (one of 800 people in the world) speaks Koro to her baby.
Why? It has to do with your brain -- the critical period from birth to age seven.
A study shows that at 6-8 month old babies don't discriminate sounds of different language, but in an amazing short time, at 10-12 month old babies turn head to sounds of a language of their own culture. It is a 2 month critical period. They are absorbing certain sounds of the language and shaping in their brain.
Researchers compare each component of nonreferential babbles with the phonetic inventory of an adult signlan. Yonekawa (1984) suggested the number of primes in each parameter such as handshape, movement and location. In a participant, 29% of handshape, and 54% of movement inventory in adult JSL were used in non0referential gestures. discuss that nonreferential babbles with the phonetic inventory of adult JSL.
Petitto and Marentette (1991) showed that 32% of the handshape and 54% of the movement that made up the phonetic inventory of adult ASL were observed in manual babbling. These nonreferential gestures are produced before the onset of signed words.
Native-sign-language people who are culturally Deaf around the world are truly living preservers of their native signed languages and culture, passing on to next generations.